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@@ -18,7 +18,7 @@
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</affiliation>
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</author>
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- <date>September 10, 2007</date>
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+ <date>Oct 15, 2007</date>
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<edition>0.3.7</edition>
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<abstract>
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@@ -67,7 +67,7 @@
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This document describes how to write an
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<ulink url="http://www.alsa-project.org/"><citetitle>
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ALSA (Advanced Linux Sound Architecture)</citetitle></ulink>
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- driver. The document focuses mainly on the PCI soundcard.
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+ driver. The document focuses mainly on PCI soundcards.
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In the case of other device types, the API might
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be different, too. However, at least the ALSA kernel API is
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consistent, and therefore it would be still a bit help for
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@@ -75,23 +75,23 @@
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</para>
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<para>
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- The target of this document is ones who already have enough
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- skill of C language and have the basic knowledge of linux
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- kernel programming. This document doesn't explain the general
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- topics of linux kernel codes and doesn't cover the detail of
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- implementation of each low-level driver. It describes only how is
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+ This document targets people who already have enough
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+ C language skills and have basic linux kernel programming
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+ knowledge. This document doesn't explain the general
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+ topic of linux kernel coding and doesn't cover low-level
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+ driver implementation details. It only describes
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the standard way to write a PCI sound driver on ALSA.
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</para>
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<para>
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- If you are already familiar with the older ALSA ver.0.5.x, you
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- can check the drivers such as <filename>es1938.c</filename> or
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- <filename>maestro3.c</filename> which have also almost the same
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+ If you are already familiar with the older ALSA ver.0.5.x API, you
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+ can check the drivers such as <filename>sound/pci/es1938.c</filename> or
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+ <filename>sound/pci/maestro3.c</filename> which have also almost the same
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code-base in the ALSA 0.5.x tree, so you can compare the differences.
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</para>
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<para>
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- This document is still a draft version. Any feedbacks and
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+ This document is still a draft version. Any feedback and
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corrections, please!!
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</para>
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</preface>
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@@ -106,7 +106,7 @@
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<section id="file-tree-general">
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<title>General</title>
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<para>
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- The ALSA drivers are provided in the two ways.
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+ The ALSA drivers are provided in two ways.
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</para>
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<para>
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@@ -114,15 +114,14 @@
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ALSA's ftp site, and another is the 2.6 (or later) Linux kernel
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tree. To synchronize both, the ALSA driver tree is split into
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two different trees: alsa-kernel and alsa-driver. The former
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- contains purely the source codes for the Linux 2.6 (or later)
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+ contains purely the source code for the Linux 2.6 (or later)
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tree. This tree is designed only for compilation on 2.6 or
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later environment. The latter, alsa-driver, contains many subtle
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- files for compiling the ALSA driver on the outside of Linux
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- kernel like configure script, the wrapper functions for older,
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- 2.2 and 2.4 kernels, to adapt the latest kernel API,
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+ files for compiling ALSA drivers outside of the Linux kernel tree,
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+ wrapper functions for older 2.2 and 2.4 kernels, to adapt the latest kernel API,
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and additional drivers which are still in development or in
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tests. The drivers in alsa-driver tree will be moved to
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- alsa-kernel (eventually 2.6 kernel tree) once when they are
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+ alsa-kernel (and eventually to the 2.6 kernel tree) when they are
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finished and confirmed to work fine.
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</para>
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@@ -168,7 +167,7 @@
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<section id="file-tree-core-directory">
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<title>core directory</title>
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<para>
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- This directory contains the middle layer, that is, the heart
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+ This directory contains the middle layer which is the heart
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of ALSA drivers. In this directory, the native ALSA modules are
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stored. The sub-directories contain different modules and are
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dependent upon the kernel config.
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@@ -181,7 +180,7 @@
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The codes for PCM and mixer OSS emulation modules are stored
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in this directory. The rawmidi OSS emulation is included in
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the ALSA rawmidi code since it's quite small. The sequencer
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- code is stored in core/seq/oss directory (see
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+ code is stored in <filename>core/seq/oss</filename> directory (see
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<link linkend="file-tree-core-directory-seq-oss"><citetitle>
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below</citetitle></link>).
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</para>
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@@ -200,7 +199,7 @@
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<section id="file-tree-core-directory-seq">
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<title>core/seq</title>
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<para>
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- This and its sub-directories are for the ALSA
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+ This directory and its sub-directories are for the ALSA
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sequencer. This directory contains the sequencer core and
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primary sequencer modules such like snd-seq-midi,
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snd-seq-virmidi, etc. They are compiled only when
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@@ -229,22 +228,22 @@
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<title>include directory</title>
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<para>
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This is the place for the public header files of ALSA drivers,
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- which are to be exported to the user-space, or included by
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+ which are to be exported to user-space, or included by
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several files at different directories. Basically, the private
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header files should not be placed in this directory, but you may
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- still find files there, due to historical reason :)
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+ still find files there, due to historical reasons :)
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</para>
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</section>
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<section id="file-tree-drivers-directory">
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<title>drivers directory</title>
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<para>
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- This directory contains the codes shared among different drivers
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- on the different architectures. They are hence supposed not to be
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+ This directory contains code shared among different drivers
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+ on different architectures. They are hence supposed not to be
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architecture-specific.
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For example, the dummy pcm driver and the serial MIDI
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driver are found in this directory. In the sub-directories,
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- there are the codes for components which are independent from
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+ there is code for components which are independent from
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bus and cpu architectures.
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</para>
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@@ -271,7 +270,7 @@
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<para>
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Although there is a standard i2c layer on Linux, ALSA has its
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- own i2c codes for some cards, because the soundcard needs only a
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+ own i2c code for some cards, because the soundcard needs only a
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simple operation and the standard i2c API is too complicated for
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such a purpose.
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</para>
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@@ -292,28 +291,28 @@
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<para>
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So far, there is only Emu8000/Emu10k1 synth driver under
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- synth/emux sub-directory.
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+ the <filename>synth/emux</filename> sub-directory.
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</para>
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</section>
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<section id="file-tree-pci-directory">
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<title>pci directory</title>
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<para>
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- This and its sub-directories hold the top-level card modules
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- for PCI soundcards and the codes specific to the PCI BUS.
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+ This directory and its sub-directories hold the top-level card modules
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+ for PCI soundcards and the code specific to the PCI BUS.
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</para>
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<para>
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- The drivers compiled from a single file is stored directly on
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- pci directory, while the drivers with several source files are
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- stored on its own sub-directory (e.g. emu10k1, ice1712).
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+ The drivers compiled from a single file are stored directly
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+ in the pci directory, while the drivers with several source files are
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+ stored on their own sub-directory (e.g. emu10k1, ice1712).
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</para>
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</section>
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<section id="file-tree-isa-directory">
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<title>isa directory</title>
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<para>
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- This and its sub-directories hold the top-level card modules
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+ This directory and its sub-directories hold the top-level card modules
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for ISA soundcards.
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</para>
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</section>
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@@ -321,16 +320,16 @@
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<section id="file-tree-arm-ppc-sparc-directories">
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<title>arm, ppc, and sparc directories</title>
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<para>
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- These are for the top-level card modules which are
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- specific to each given architecture.
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+ They are used for top-level card modules which are
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+ specific to one of these architectures.
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</para>
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</section>
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<section id="file-tree-usb-directory">
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<title>usb directory</title>
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<para>
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- This contains the USB-audio driver. On the latest version, the
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- USB MIDI driver is integrated together with usb-audio driver.
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+ This directory contains the USB-audio driver. In the latest version, the
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+ USB MIDI driver is integrated in the usb-audio driver.
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</para>
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</section>
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@@ -338,16 +337,17 @@
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<title>pcmcia directory</title>
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<para>
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The PCMCIA, especially PCCard drivers will go here. CardBus
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- drivers will be on pci directory, because its API is identical
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- with the standard PCI cards.
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+ drivers will be in the pci directory, because their API is identical
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+ to that of standard PCI cards.
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</para>
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</section>
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<section id="file-tree-oss-directory">
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<title>oss directory</title>
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<para>
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- The OSS/Lite source files are stored here on Linux 2.6 (or
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- later) tree. (In the ALSA driver tarball, it's empty, of course :)
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+ The OSS/Lite source files are stored here in Linux 2.6 (or
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+ later) tree. In the ALSA driver tarball, this directory is empty,
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+ of course :)
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</para>
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</section>
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</chapter>
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@@ -362,7 +362,7 @@
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<section id="basic-flow-outline">
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<title>Outline</title>
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<para>
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- The minimum flow of PCI soundcard is like the following:
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+ The minimum flow for PCI soundcards is as follows:
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<itemizedlist>
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<listitem><para>define the PCI ID table (see the section
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@@ -370,9 +370,13 @@
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</citetitle></link>).</para></listitem>
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<listitem><para>create <function>probe()</function> callback.</para></listitem>
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<listitem><para>create <function>remove()</function> callback.</para></listitem>
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- <listitem><para>create pci_driver table which contains the three pointers above.</para></listitem>
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- <listitem><para>create <function>init()</function> function just calling <function>pci_register_driver()</function> to register the pci_driver table defined above.</para></listitem>
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- <listitem><para>create <function>exit()</function> function to call <function>pci_unregister_driver()</function> function.</para></listitem>
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+ <listitem><para>create a <structname>pci_driver</structname> structure
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+ containing the three pointers above.</para></listitem>
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+ <listitem><para>create an <function>init()</function> function just calling
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+ the <function>pci_register_driver()</function> to register the pci_driver table
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+ defined above.</para></listitem>
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+ <listitem><para>create an <function>exit()</function> function to call
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+ the <function>pci_unregister_driver()</function> function.</para></listitem>
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</itemizedlist>
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</para>
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</section>
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@@ -382,15 +386,14 @@
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<para>
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The code example is shown below. Some parts are kept
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unimplemented at this moment but will be filled in the
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- succeeding sections. The numbers in comment lines of
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- <function>snd_mychip_probe()</function> function are the
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- markers.
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+ next sections. The numbers in the comment lines of the
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+ <function>snd_mychip_probe()</function> function
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+ refer to details explained in the following section.
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<example>
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- <title>Basic Flow for PCI Drivers Example</title>
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+ <title>Basic Flow for PCI Drivers - Example</title>
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<programlisting>
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<![CDATA[
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- #include <sound/driver.h>
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#include <linux/init.h>
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#include <linux/pci.h>
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#include <linux/slab.h>
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@@ -398,6 +401,7 @@
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#include <sound/initval.h>
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/* module parameters (see "Module Parameters") */
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+ /* SNDRV_CARDS: maximum number of cards supported by this module */
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static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX;
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static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR;
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static int enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP;
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@@ -405,13 +409,13 @@
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/* definition of the chip-specific record */
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struct mychip {
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struct snd_card *card;
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- /* rest of implementation will be in the section
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- * "PCI Resource Managements"
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+ /* the rest of the implementation will be in section
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+ * "PCI Resource Management"
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*/
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};
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/* chip-specific destructor
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- * (see "PCI Resource Managements")
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+ * (see "PCI Resource Management")
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*/
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static int snd_mychip_free(struct mychip *chip)
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{
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@@ -442,7 +446,7 @@
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*rchip = NULL;
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/* check PCI availability here
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- * (see "PCI Resource Managements")
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+ * (see "PCI Resource Management")
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*/
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....
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@@ -454,7 +458,7 @@
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chip->card = card;
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/* rest of initialization here; will be implemented
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- * later, see "PCI Resource Managements"
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+ * later, see "PCI Resource Management"
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*/
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....
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@@ -521,7 +525,7 @@
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return 0;
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}
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- /* destructor -- see "Destructor" sub-section */
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+ /* destructor -- see the "Destructor" sub-section */
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static void __devexit snd_mychip_remove(struct pci_dev *pci)
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{
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snd_card_free(pci_get_drvdata(pci));
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@@ -536,16 +540,16 @@
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<section id="basic-flow-constructor">
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<title>Constructor</title>
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<para>
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- The real constructor of PCI drivers is probe callback. The
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- probe callback and other component-constructors which are called
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- from probe callback should be defined with
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- <parameter>__devinit</parameter> prefix. You
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- cannot use <parameter>__init</parameter> prefix for them,
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+ The real constructor of PCI drivers is the <function>probe</function> callback.
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+ The <function>probe</function> callback and other component-constructors which are called
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+ from the <function>probe</function> callback should be defined with
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+ the <parameter>__devinit</parameter> prefix. You
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+ cannot use the <parameter>__init</parameter> prefix for them,
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because any PCI device could be a hotplug device.
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</para>
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<para>
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- In the probe callback, the following scheme is often used.
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+ In the <function>probe</function> callback, the following scheme is often used.
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</para>
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<section id="basic-flow-constructor-device-index">
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@@ -570,7 +574,7 @@
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</para>
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<para>
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- At each time probe callback is called, check the
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+ Each time the <function>probe</function> callback is called, check the
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availability of the device. If not available, simply increment
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the device index and returns. dev will be incremented also
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later (<link
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@@ -594,7 +598,7 @@
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</para>
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<para>
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- The detail will be explained in the section
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+ The details will be explained in the section
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<link linkend="card-management-card-instance"><citetitle>
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Management of Cards and Components</citetitle></link>.
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</para>
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@@ -619,9 +623,9 @@
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</programlisting>
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</informalexample>
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- The detail will be explained in the section <link
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+ The details will be explained in the section <link
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linkend="pci-resource"><citetitle>PCI Resource
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- Managements</citetitle></link>.
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+ Management</citetitle></link>.
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</para>
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</section>
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@@ -640,7 +644,7 @@
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</informalexample>
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The driver field holds the minimal ID string of the
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- chip. This is referred by alsa-lib's configurator, so keep it
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+ chip. This is used by alsa-lib's configurator, so keep it
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simple but unique.
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Even the same driver can have different driver IDs to
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distinguish the functionality of each chip type.
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@@ -648,7 +652,7 @@
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<para>
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The shortname field is a string shown as more verbose
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- name. The longname field contains the information which is
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+ name. The longname field contains the information
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shown in <filename>/proc/asound/cards</filename>.
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</para>
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</section>
|
|
|
@@ -703,7 +707,7 @@
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</informalexample>
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In the above, the card record is stored. This pointer is
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- referred in the remove callback and power-management
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+ used in the remove callback and power-management
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callbacks, too.
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</para>
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</section>
|
|
|
@@ -746,7 +750,6 @@
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<informalexample>
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<programlisting>
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<![CDATA[
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- #include <sound/driver.h>
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#include <linux/init.h>
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#include <linux/pci.h>
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#include <linux/slab.h>
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@@ -757,22 +760,22 @@
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</informalexample>
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where the last one is necessary only when module options are
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- defined in the source file. If the codes are split to several
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- files, the file without module options don't need them.
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+ defined in the source file. If the code is split into several
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+ files, the files without module options don't need them.
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</para>
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<para>
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- In addition to them, you'll need
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- <filename><linux/interrupt.h></filename> for the interrupt
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- handling, and <filename><asm/io.h></filename> for the i/o
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- access. If you use <function>mdelay()</function> or
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+ In addition to these headers, you'll need
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+ <filename><linux/interrupt.h></filename> for interrupt
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+ handling, and <filename><asm/io.h></filename> for I/O
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+ access. If you use the <function>mdelay()</function> or
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<function>udelay()</function> functions, you'll need to include
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- <filename><linux/delay.h></filename>, too.
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+ <filename><linux/delay.h></filename> too.
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</para>
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<para>
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- The ALSA interfaces like PCM or control API are defined in other
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- header files as <filename><sound/xxx.h></filename>.
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+ The ALSA interfaces like the PCM and control APIs are defined in other
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+ <filename><sound/xxx.h></filename> header files.
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They have to be included after
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<filename><sound/core.h></filename>.
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</para>
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@@ -795,12 +798,12 @@
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<para>
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A card record is the headquarters of the soundcard. It manages
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- the list of whole devices (components) on the soundcard, such as
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+ the whole list of devices (components) on the soundcard, such as
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PCM, mixers, MIDI, synthesizer, and so on. Also, the card
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record holds the ID and the name strings of the card, manages
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the root of proc files, and controls the power-management states
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and hotplug disconnections. The component list on the card
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- record is used to manage the proper releases of resources at
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+ record is used to manage the correct release of resources at
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destruction.
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</para>
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@@ -824,9 +827,8 @@
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<constant>THIS_MODULE</constant>),
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and the size of extra-data space. The last argument is used to
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allocate card->private_data for the
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- chip-specific data. Note that this data
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- <emphasis>is</emphasis> allocated by
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- <function>snd_card_new()</function>.
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+ chip-specific data. Note that these data
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+ are allocated by <function>snd_card_new()</function>.
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</para>
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</section>
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@@ -834,10 +836,10 @@
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<title>Components</title>
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<para>
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After the card is created, you can attach the components
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- (devices) to the card instance. On ALSA driver, a component is
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+ (devices) to the card instance. In an ALSA driver, a component is
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represented as a struct <structname>snd_device</structname> object.
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A component can be a PCM instance, a control interface, a raw
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- MIDI interface, etc. Each of such instances has one component
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+ MIDI interface, etc. Each such instance has one component
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entry.
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</para>
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@@ -859,7 +861,7 @@
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(<constant>SNDRV_DEV_XXX</constant>), the data pointer, and the
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callback pointers (<parameter>&ops</parameter>). The
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device-level defines the type of components and the order of
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- registration and de-registration. For most of components, the
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+ registration and de-registration. For most components, the
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device-level is already defined. For a user-defined component,
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you can use <constant>SNDRV_DEV_LOWLEVEL</constant>.
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</para>
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@@ -867,13 +869,13 @@
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<para>
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This function itself doesn't allocate the data space. The data
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must be allocated manually beforehand, and its pointer is passed
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- as the argument. This pointer is used as the identifier
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- (<parameter>chip</parameter> in the above example) for the
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- instance.
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+ as the argument. This pointer is used as the
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+ (<parameter>chip</parameter> identifier in the above example)
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+ for the instance.
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</para>
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<para>
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- Each ALSA pre-defined component such as ac97 or pcm calls
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+ Each pre-defined ALSA component such as ac97 and pcm calls
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<function>snd_device_new()</function> inside its
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constructor. The destructor for each component is defined in the
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callback pointers. Hence, you don't need to take care of
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@@ -881,19 +883,19 @@
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</para>
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<para>
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- If you would like to create your own component, you need to
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- set the destructor function to dev_free callback in
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- <parameter>ops</parameter>, so that it can be released
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- automatically via <function>snd_card_free()</function>. The
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- example will be shown later as an implementation of a
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- chip-specific data.
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+ If you wish to create your own component, you need to
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+ set the destructor function to the dev_free callback in
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+ the <parameter>ops</parameter>, so that it can be released
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+ automatically via <function>snd_card_free()</function>.
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+ The next example will show an implementation of chip-specific
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+ data.
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</para>
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</section>
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<section id="card-management-chip-specific">
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<title>Chip-Specific Data</title>
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<para>
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- The chip-specific information, e.g. the i/o port address, its
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+ Chip-specific information, e.g. the I/O port address, its
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resource pointer, or the irq number, is stored in the
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chip-specific record.
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@@ -909,13 +911,14 @@
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</para>
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<para>
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- In general, there are two ways to allocate the chip record.
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+ In general, there are two ways of allocating the chip record.
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</para>
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<section id="card-management-chip-specific-snd-card-new">
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<title>1. Allocating via <function>snd_card_new()</function>.</title>
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<para>
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- As mentioned above, you can pass the extra-data-length to the 4th argument of <function>snd_card_new()</function>, i.e.
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+ As mentioned above, you can pass the extra-data-length
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+ to the 4th argument of <function>snd_card_new()</function>, i.e.
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<informalexample>
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<programlisting>
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@@ -925,7 +928,7 @@
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</programlisting>
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</informalexample>
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- whether struct <structname>mychip</structname> is the type of the chip record.
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+ struct <structname>mychip</structname> is the type of the chip record.
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</para>
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<para>
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@@ -1037,8 +1040,8 @@
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<title>Registration and Release</title>
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<para>
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After all components are assigned, register the card instance
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- by calling <function>snd_card_register()</function>. The access
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- to the device files are enabled at this point. That is, before
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+ by calling <function>snd_card_register()</function>. Access
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+ to the device files is enabled at this point. That is, before
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<function>snd_card_register()</function> is called, the
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components are safely inaccessible from external side. If this
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call fails, exit the probe function after releasing the card via
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@@ -1047,7 +1050,7 @@
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<para>
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For releasing the card instance, you can call simply
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- <function>snd_card_free()</function>. As already mentioned, all
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+ <function>snd_card_free()</function>. As mentioned earlier, all
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components are released automatically by this call.
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</para>
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@@ -1055,7 +1058,7 @@
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As further notes, the destructors (both
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<function>snd_mychip_dev_free</function> and
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<function>snd_mychip_free</function>) cannot be defined with
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- <parameter>__devexit</parameter> prefix, because they may be
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+ the <parameter>__devexit</parameter> prefix, because they may be
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called from the constructor, too, at the false path.
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</para>
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@@ -1071,20 +1074,20 @@
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<!-- ****************************************************** -->
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-<!-- PCI Resource Managements -->
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+<!-- PCI Resource Management -->
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<!-- ****************************************************** -->
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<chapter id="pci-resource">
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- <title>PCI Resource Managements</title>
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+ <title>PCI Resource Management</title>
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<section id="pci-resource-example">
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<title>Full Code Example</title>
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<para>
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- In this section, we'll finish the chip-specific constructor,
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- destructor and PCI entries. The example code is shown first,
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+ In this section, we'll complete the chip-specific constructor,
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+ destructor and PCI entries. Example code is shown first,
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below.
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<example>
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- <title>PCI Resource Managements Example</title>
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+ <title>PCI Resource Management Example</title>
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<programlisting>
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<![CDATA[
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struct mychip {
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@@ -1103,7 +1106,7 @@
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/* release the irq */
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if (chip->irq >= 0)
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free_irq(chip->irq, chip);
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- /* release the i/o ports & memory */
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+ /* release the I/O ports & memory */
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pci_release_regions(chip->pci);
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/* disable the PCI entry */
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pci_disable_device(chip->pci);
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@@ -1196,13 +1199,13 @@
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.remove = __devexit_p(snd_mychip_remove),
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};
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- /* initialization of the module */
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+ /* module initialization */
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static int __init alsa_card_mychip_init(void)
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{
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return pci_register_driver(&driver);
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}
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- /* clean up the module */
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+ /* module clean up */
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static void __exit alsa_card_mychip_exit(void)
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{
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pci_unregister_driver(&driver);
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@@ -1228,10 +1231,10 @@
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</para>
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<para>
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- In the case of PCI devices, you have to call at first
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- <function>pci_enable_device()</function> function before
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+ In the case of PCI devices, you first have to call
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+ the <function>pci_enable_device()</function> function before
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allocating resources. Also, you need to set the proper PCI DMA
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- mask to limit the accessed i/o range. In some cases, you might
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+ mask to limit the accessed I/O range. In some cases, you might
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need to call <function>pci_set_master()</function> function,
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too.
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</para>
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@@ -1261,15 +1264,15 @@
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<section id="pci-resource-resource-allocation">
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<title>Resource Allocation</title>
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<para>
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- The allocation of I/O ports and irqs are done via standard kernel
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+ The allocation of I/O ports and irqs is done via standard kernel
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functions. Unlike ALSA ver.0.5.x., there are no helpers for
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that. And these resources must be released in the destructor
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function (see below). Also, on ALSA 0.9.x, you don't need to
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- allocate (pseudo-)DMA for PCI like ALSA 0.5.x.
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+ allocate (pseudo-)DMA for PCI like in ALSA 0.5.x.
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</para>
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<para>
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- Now assume that this PCI device has an I/O port with 8 bytes
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+ Now assume that the PCI device has an I/O port with 8 bytes
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and an interrupt. Then struct <structname>mychip</structname> will have the
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following fields:
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@@ -1288,7 +1291,7 @@
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</para>
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<para>
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- For an i/o port (and also a memory region), you need to have
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+ For an I/O port (and also a memory region), you need to have
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the resource pointer for the standard resource management. For
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an irq, you have to keep only the irq number (integer). But you
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need to initialize this number as -1 before actual allocation,
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@@ -1299,7 +1302,7 @@
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</para>
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<para>
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- The allocation of an i/o port is done like this:
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+ The allocation of an I/O port is done like this:
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<informalexample>
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<programlisting>
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@@ -1318,12 +1321,12 @@
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<para>
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<!-- obsolete -->
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- It will reserve the i/o port region of 8 bytes of the given
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+ It will reserve the I/O port region of 8 bytes of the given
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PCI device. The returned value, chip->res_port, is allocated
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via <function>kmalloc()</function> by
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<function>request_region()</function>. The pointer must be
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- released via <function>kfree()</function>, but there is some
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- problem regarding this. This issue will be explained more below.
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+ released via <function>kfree()</function>, but there is a
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+ problem with this. This issue will be explained later.
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</para>
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<para>
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@@ -1351,8 +1354,8 @@
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</para>
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<para>
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- On the PCI bus, the interrupts can be shared. Thus,
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- <constant>IRQF_SHARED</constant> is given as the interrupt flag of
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+ On the PCI bus, interrupts can be shared. Thus,
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+ <constant>IRQF_SHARED</constant> is used as the interrupt flag of
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<function>request_irq()</function>.
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</para>
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@@ -1364,7 +1367,7 @@
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</para>
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<para>
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- I won't define the detail of the interrupt handler at this
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+ I won't give details about the interrupt handler at this
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point, but at least its appearance can be explained now. The
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interrupt handler looks usually like the following:
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@@ -1386,11 +1389,11 @@
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Now let's write the corresponding destructor for the resources
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above. The role of destructor is simple: disable the hardware
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(if already activated) and release the resources. So far, we
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- have no hardware part, so the disabling is not written here.
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+ have no hardware part, so the disabling code is not written here.
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</para>
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<para>
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- For releasing the resources, <quote>check-and-release</quote>
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+ To release the resources, the <quote>check-and-release</quote>
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method is a safer way. For the interrupt, do like this:
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<informalexample>
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@@ -1410,7 +1413,7 @@
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<para>
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When you requested I/O ports or memory regions via
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<function>pci_request_region()</function> or
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- <function>pci_request_regions()</function> like this example,
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+ <function>pci_request_regions()</function> like in this example,
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release the resource(s) using the corresponding function,
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<function>pci_release_region()</function> or
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<function>pci_release_regions()</function>.
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@@ -1429,7 +1432,7 @@
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or <function>request_mem_region</function>, you can release it via
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<function>release_resource()</function>. Suppose that you keep
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the resource pointer returned from <function>request_region()</function>
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- in chip->res_port, the release procedure looks like below:
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+ in chip->res_port, the release procedure looks like:
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|
<informalexample>
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<programlisting>
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@@ -1442,7 +1445,7 @@
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<para>
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Don't forget to call <function>pci_disable_device()</function>
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- before all finished.
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+ before the end.
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</para>
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<para>
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@@ -1459,14 +1462,14 @@
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<para>
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Again, remember that you cannot
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- set <parameter>__devexit</parameter> prefix for this destructor.
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+ use the <parameter>__devexit</parameter> prefix for this destructor.
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</para>
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<para>
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- We didn't implement the hardware-disabling part in the above.
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+ We didn't implement the hardware disabling part in the above.
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|
If you need to do this, please note that the destructor may be
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called even before the initialization of the chip is completed.
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- It would be better to have a flag to skip the hardware-disabling
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+ It would be better to have a flag to skip hardware disabling
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if the hardware was not initialized yet.
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</para>
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|
|
@@ -1475,14 +1478,14 @@
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|
<function>snd_device_new()</function> with
|
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|
<constant>SNDRV_DEV_LOWLELVEL</constant> , its destructor is
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|
called at the last. That is, it is assured that all other
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- components like PCMs and controls have been already released.
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- You don't have to call stopping PCMs, etc. explicitly, but just
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- stop the hardware in the low-level.
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+ components like PCMs and controls have already been released.
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+ You don't have to stop PCMs, etc. explicitly, but just
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+ call low-level hardware stopping.
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</para>
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<para>
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|
|
The management of a memory-mapped region is almost as same as
|
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|
- the management of an i/o port. You'll need three fields like
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+ the management of an I/O port. You'll need three fields like
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|
|
the following:
|
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|
|
|
<informalexample>
|
|
|
@@ -1561,8 +1564,8 @@
|
|
|
<section id="pci-resource-entries">
|
|
|
<title>PCI Entries</title>
|
|
|
<para>
|
|
|
- So far, so good. Let's finish the rest of missing PCI
|
|
|
- stuffs. At first, we need a
|
|
|
+ So far, so good. Let's finish the missing PCI
|
|
|
+ stuff. At first, we need a
|
|
|
<structname>pci_device_id</structname> table for this
|
|
|
chipset. It's a table of PCI vendor/device ID number, and some
|
|
|
masks.
|
|
|
@@ -1588,13 +1591,13 @@
|
|
|
|
|
|
<para>
|
|
|
The first and second fields of
|
|
|
- <structname>pci_device_id</structname> struct are the vendor and
|
|
|
- device IDs. If you have nothing special to filter the matching
|
|
|
- devices, you can use the rest of fields like above. The last
|
|
|
- field of <structname>pci_device_id</structname> struct is a
|
|
|
+ the <structname>pci_device_id</structname> structure are the vendor and
|
|
|
+ device IDs. If you have no reason to filter the matching
|
|
|
+ devices, you can leave the remaining fields as above. The last
|
|
|
+ field of the <structname>pci_device_id</structname> struct contains
|
|
|
private data for this entry. You can specify any value here, for
|
|
|
- example, to tell the type of different operations per each
|
|
|
- device IDs. Such an example is found in intel8x0 driver.
|
|
|
+ example, to define specific operations for supported device IDs.
|
|
|
+ Such an example is found in the intel8x0 driver.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
@@ -1621,10 +1624,10 @@
|
|
|
|
|
|
<para>
|
|
|
The <structfield>probe</structfield> and
|
|
|
- <structfield>remove</structfield> functions are what we already
|
|
|
- defined in
|
|
|
- the previous sections. The <structfield>remove</structfield> should
|
|
|
- be defined with
|
|
|
+ <structfield>remove</structfield> functions have already
|
|
|
+ been defined in the previous sections.
|
|
|
+ The <structfield>remove</structfield> function should
|
|
|
+ be defined with the
|
|
|
<function>__devexit_p()</function> macro, so that it's not
|
|
|
defined for built-in (and non-hot-pluggable) case. The
|
|
|
<structfield>name</structfield>
|
|
|
@@ -1665,8 +1668,7 @@
|
|
|
|
|
|
<para>
|
|
|
Oh, one thing was forgotten. If you have no exported symbols,
|
|
|
- you need to declare it on 2.2 or 2.4 kernels (on 2.6 kernels
|
|
|
- it's not necessary, though).
|
|
|
+ you need to declare it in 2.2 or 2.4 kernels (it's not necessary in 2.6 kernels).
|
|
|
|
|
|
<informalexample>
|
|
|
<programlisting>
|
|
|
@@ -1698,7 +1700,7 @@
|
|
|
|
|
|
<para>
|
|
|
For accessing to the PCM layer, you need to include
|
|
|
- <filename><sound/pcm.h></filename> above all. In addition,
|
|
|
+ <filename><sound/pcm.h></filename> first. In addition,
|
|
|
<filename><sound/pcm_params.h></filename> might be needed
|
|
|
if you access to some functions related with hw_param.
|
|
|
</para>
|
|
|
@@ -1707,21 +1709,21 @@
|
|
|
Each card device can have up to four pcm instances. A pcm
|
|
|
instance corresponds to a pcm device file. The limitation of
|
|
|
number of instances comes only from the available bit size of
|
|
|
- the linux's device number. Once when 64bit device number is
|
|
|
- used, we'll have more available pcm instances.
|
|
|
+ the Linux's device numbers. Once when 64bit device number is
|
|
|
+ used, we'll have more pcm instances available.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
A pcm instance consists of pcm playback and capture streams,
|
|
|
and each pcm stream consists of one or more pcm substreams. Some
|
|
|
- soundcard supports the multiple-playback function. For example,
|
|
|
+ soundcards support multiple playback functions. For example,
|
|
|
emu10k1 has a PCM playback of 32 stereo substreams. In this case, at
|
|
|
each open, a free substream is (usually) automatically chosen
|
|
|
and opened. Meanwhile, when only one substream exists and it was
|
|
|
- already opened, the succeeding open will result in the blocking
|
|
|
- or the error with <constant>EAGAIN</constant> according to the
|
|
|
- file open mode. But you don't have to know the detail in your
|
|
|
- driver. The PCM middle layer will take all such jobs.
|
|
|
+ already opened, the successful open will either block
|
|
|
+ or error with <constant>EAGAIN</constant> according to the
|
|
|
+ file open mode. But you don't have to care about such details in your
|
|
|
+ driver. The PCM middle layer will take care of such work.
|
|
|
</para>
|
|
|
</section>
|
|
|
|
|
|
@@ -1944,7 +1946,7 @@
|
|
|
<section id="pcm-interface-constructor">
|
|
|
<title>Constructor</title>
|
|
|
<para>
|
|
|
- A pcm instance is allocated by <function>snd_pcm_new()</function>
|
|
|
+ A pcm instance is allocated by the <function>snd_pcm_new()</function>
|
|
|
function. It would be better to create a constructor for pcm,
|
|
|
namely,
|
|
|
|
|
|
@@ -1971,23 +1973,23 @@
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- The <function>snd_pcm_new()</function> function takes the four
|
|
|
+ The <function>snd_pcm_new()</function> function takes four
|
|
|
arguments. The first argument is the card pointer to which this
|
|
|
pcm is assigned, and the second is the ID string.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
The third argument (<parameter>index</parameter>, 0 in the
|
|
|
- above) is the index of this new pcm. It begins from zero. When
|
|
|
- you will create more than one pcm instances, specify the
|
|
|
+ above) is the index of this new pcm. It begins from zero. If
|
|
|
+ you create more than one pcm instances, specify the
|
|
|
different numbers in this argument. For example,
|
|
|
<parameter>index</parameter> = 1 for the second PCM device.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
The fourth and fifth arguments are the number of substreams
|
|
|
- for playback and capture, respectively. Here both 1 are given in
|
|
|
- the above example. When no playback or no capture is available,
|
|
|
+ for playback and capture, respectively. Here 1 is used for
|
|
|
+ both arguments. When no playback or capture substreams are available,
|
|
|
pass 0 to the corresponding argument.
|
|
|
</para>
|
|
|
|
|
|
@@ -2045,13 +2047,13 @@
|
|
|
</programlisting>
|
|
|
</informalexample>
|
|
|
|
|
|
- Each of callbacks is explained in the subsection
|
|
|
+ All the callbacks are described in the
|
|
|
<link linkend="pcm-interface-operators"><citetitle>
|
|
|
- Operators</citetitle></link>.
|
|
|
+ Operators</citetitle></link> subsection.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- After setting the operators, most likely you'd like to
|
|
|
+ After setting the operators, you probably will want to
|
|
|
pre-allocate the buffer. For the pre-allocation, simply call
|
|
|
the following:
|
|
|
|
|
|
@@ -2065,8 +2067,8 @@
|
|
|
</programlisting>
|
|
|
</informalexample>
|
|
|
|
|
|
- It will allocate up to 64kB buffer as default. The details of
|
|
|
- buffer management will be described in the later section <link
|
|
|
+ It will allocate a buffer up to 64kB as default.
|
|
|
+ Buffer management details will be described in the later section <link
|
|
|
linkend="buffer-and-memory"><citetitle>Buffer and Memory
|
|
|
Management</citetitle></link>.
|
|
|
</para>
|
|
|
@@ -2095,13 +2097,13 @@
|
|
|
<para>
|
|
|
The destructor for a pcm instance is not always
|
|
|
necessary. Since the pcm device will be released by the middle
|
|
|
- layer code automatically, you don't have to call destructor
|
|
|
+ layer code automatically, you don't have to call the destructor
|
|
|
explicitly.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- The destructor would be necessary when you created some
|
|
|
- special records internally and need to release them. In such a
|
|
|
+ The destructor would be necessary if you created
|
|
|
+ special records internally and needed to release them. In such a
|
|
|
case, set the destructor function to
|
|
|
pcm->private_free:
|
|
|
|
|
|
@@ -2141,16 +2143,15 @@
|
|
|
When the PCM substream is opened, a PCM runtime instance is
|
|
|
allocated and assigned to the substream. This pointer is
|
|
|
accessible via <constant>substream->runtime</constant>.
|
|
|
- This runtime pointer holds the various information; it holds
|
|
|
- the copy of hw_params and sw_params configurations, the buffer
|
|
|
- pointers, mmap records, spinlocks, etc. Almost everything you
|
|
|
- need for controlling the PCM can be found there.
|
|
|
+ This runtime pointer holds most information you need
|
|
|
+ to control the PCM: the copy of hw_params and sw_params configurations, the buffer
|
|
|
+ pointers, mmap records, spinlocks, etc.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
The definition of runtime instance is found in
|
|
|
- <filename><sound/pcm.h></filename>. Here is the
|
|
|
- copy from the file.
|
|
|
+ <filename><sound/pcm.h></filename>. Here are
|
|
|
+ the contents of this file:
|
|
|
<informalexample>
|
|
|
<programlisting>
|
|
|
<![CDATA[
|
|
|
@@ -2185,7 +2186,6 @@ struct _snd_pcm_runtime {
|
|
|
struct timespec tstamp_mode; /* mmap timestamp is updated */
|
|
|
unsigned int period_step;
|
|
|
unsigned int sleep_min; /* min ticks to sleep */
|
|
|
- snd_pcm_uframes_t xfer_align; /* xfer size need to be a multiple */
|
|
|
snd_pcm_uframes_t start_threshold;
|
|
|
snd_pcm_uframes_t stop_threshold;
|
|
|
snd_pcm_uframes_t silence_threshold; /* Silence filling happens when
|
|
|
@@ -2244,7 +2244,7 @@ struct _snd_pcm_runtime {
|
|
|
<para>
|
|
|
For the operators (callbacks) of each sound driver, most of
|
|
|
these records are supposed to be read-only. Only the PCM
|
|
|
- middle-layer changes / updates these info. The exceptions are
|
|
|
+ middle-layer changes / updates them. The exceptions are
|
|
|
the hardware description (hw), interrupt callbacks
|
|
|
(transfer_ack_xxx), DMA buffer information, and the private
|
|
|
data. Besides, if you use the standard buffer allocation
|
|
|
@@ -2285,7 +2285,7 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- Typically, you'll have a hardware descriptor like below:
|
|
|
+ Typically, you'll have a hardware descriptor as below:
|
|
|
<informalexample>
|
|
|
<programlisting>
|
|
|
<![CDATA[
|
|
|
@@ -2320,10 +2320,10 @@ struct _snd_pcm_runtime {
|
|
|
<constant>SNDRV_PCM_INFO_XXX</constant>. Here, at least, you
|
|
|
have to specify whether the mmap is supported and which
|
|
|
interleaved format is supported.
|
|
|
- When the mmap is supported, add
|
|
|
+ When the is supported, add the
|
|
|
<constant>SNDRV_PCM_INFO_MMAP</constant> flag here. When the
|
|
|
hardware supports the interleaved or the non-interleaved
|
|
|
- format, <constant>SNDRV_PCM_INFO_INTERLEAVED</constant> or
|
|
|
+ formats, <constant>SNDRV_PCM_INFO_INTERLEAVED</constant> or
|
|
|
<constant>SNDRV_PCM_INFO_NONINTERLEAVED</constant> flag must
|
|
|
be set, respectively. If both are supported, you can set both,
|
|
|
too.
|
|
|
@@ -2331,7 +2331,7 @@ struct _snd_pcm_runtime {
|
|
|
|
|
|
<para>
|
|
|
In the above example, <constant>MMAP_VALID</constant> and
|
|
|
- <constant>BLOCK_TRANSFER</constant> are specified for OSS mmap
|
|
|
+ <constant>BLOCK_TRANSFER</constant> are specified for the OSS mmap
|
|
|
mode. Usually both are set. Of course,
|
|
|
<constant>MMAP_VALID</constant> is set only if the mmap is
|
|
|
really supported.
|
|
|
@@ -2345,11 +2345,11 @@ struct _snd_pcm_runtime {
|
|
|
<quote>pause</quote> operation, while the
|
|
|
<constant>RESUME</constant> bit means that the pcm supports
|
|
|
the full <quote>suspend/resume</quote> operation.
|
|
|
- If <constant>PAUSE</constant> flag is set,
|
|
|
+ If the <constant>PAUSE</constant> flag is set,
|
|
|
the <structfield>trigger</structfield> callback below
|
|
|
must handle the corresponding (pause push/release) commands.
|
|
|
The suspend/resume trigger commands can be defined even without
|
|
|
- <constant>RESUME</constant> flag. See <link
|
|
|
+ the <constant>RESUME</constant> flag. See <link
|
|
|
linkend="power-management"><citetitle>
|
|
|
Power Management</citetitle></link> section for details.
|
|
|
</para>
|
|
|
@@ -2382,7 +2382,7 @@ struct _snd_pcm_runtime {
|
|
|
<constant>CONTINUOUS</constant> bit additionally.
|
|
|
The pre-defined rate bits are provided only for typical
|
|
|
rates. If your chip supports unconventional rates, you need to add
|
|
|
- <constant>KNOT</constant> bit and set up the hardware
|
|
|
+ the <constant>KNOT</constant> bit and set up the hardware
|
|
|
constraint manually (explained later).
|
|
|
</para>
|
|
|
</listitem>
|
|
|
@@ -2390,8 +2390,8 @@ struct _snd_pcm_runtime {
|
|
|
<listitem>
|
|
|
<para>
|
|
|
<structfield>rate_min</structfield> and
|
|
|
- <structfield>rate_max</structfield> define the minimal and
|
|
|
- maximal sample rate. This should correspond somehow to
|
|
|
+ <structfield>rate_max</structfield> define the minimum and
|
|
|
+ maximum sample rate. This should correspond somehow to
|
|
|
<structfield>rates</structfield> bits.
|
|
|
</para>
|
|
|
</listitem>
|
|
|
@@ -2400,7 +2400,7 @@ struct _snd_pcm_runtime {
|
|
|
<para>
|
|
|
<structfield>channel_min</structfield> and
|
|
|
<structfield>channel_max</structfield>
|
|
|
- define, as you might already expected, the minimal and maximal
|
|
|
+ define, as you might already expected, the minimum and maximum
|
|
|
number of channels.
|
|
|
</para>
|
|
|
</listitem>
|
|
|
@@ -2408,21 +2408,21 @@ struct _snd_pcm_runtime {
|
|
|
<listitem>
|
|
|
<para>
|
|
|
<structfield>buffer_bytes_max</structfield> defines the
|
|
|
- maximal buffer size in bytes. There is no
|
|
|
+ maximum buffer size in bytes. There is no
|
|
|
<structfield>buffer_bytes_min</structfield> field, since
|
|
|
- it can be calculated from the minimal period size and the
|
|
|
- minimal number of periods.
|
|
|
+ it can be calculated from the minimum period size and the
|
|
|
+ minimum number of periods.
|
|
|
Meanwhile, <structfield>period_bytes_min</structfield> and
|
|
|
- define the minimal and maximal size of the period in bytes.
|
|
|
+ define the minimum and maximum size of the period in bytes.
|
|
|
<structfield>periods_max</structfield> and
|
|
|
- <structfield>periods_min</structfield> define the maximal and
|
|
|
- minimal number of periods in the buffer.
|
|
|
+ <structfield>periods_min</structfield> define the maximum and
|
|
|
+ minimum number of periods in the buffer.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- The <quote>period</quote> is a term, that corresponds to
|
|
|
- fragment in the OSS world. The period defines the size at
|
|
|
- which the PCM interrupt is generated. This size strongly
|
|
|
+ The <quote>period</quote> is a term that corresponds to
|
|
|
+ a fragment in the OSS world. The period defines the size at
|
|
|
+ which a PCM interrupt is generated. This size strongly
|
|
|
depends on the hardware.
|
|
|
Generally, the smaller period size will give you more
|
|
|
interrupts, that is, more controls.
|
|
|
@@ -2435,8 +2435,8 @@ struct _snd_pcm_runtime {
|
|
|
<listitem>
|
|
|
<para>
|
|
|
There is also a field <structfield>fifo_size</structfield>.
|
|
|
- This specifies the size of the hardware FIFO, but it's not
|
|
|
- used currently in the driver nor in the alsa-lib. So, you
|
|
|
+ This specifies the size of the hardware FIFO, but currently it
|
|
|
+ is neither used in the driver nor in the alsa-lib. So, you
|
|
|
can ignore this field.
|
|
|
</para>
|
|
|
</listitem>
|
|
|
@@ -2450,7 +2450,7 @@ struct _snd_pcm_runtime {
|
|
|
Ok, let's go back again to the PCM runtime records.
|
|
|
The most frequently referred records in the runtime instance are
|
|
|
the PCM configurations.
|
|
|
- The PCM configurations are stored on runtime instance
|
|
|
+ The PCM configurations are stored in the runtime instance
|
|
|
after the application sends <type>hw_params</type> data via
|
|
|
alsa-lib. There are many fields copied from hw_params and
|
|
|
sw_params structs. For example,
|
|
|
@@ -2461,11 +2461,11 @@ struct _snd_pcm_runtime {
|
|
|
|
|
|
<para>
|
|
|
One thing to be noted is that the configured buffer and period
|
|
|
- sizes are stored in <quote>frames</quote> in the runtime
|
|
|
+ sizes are stored in <quote>frames</quote> in the runtime.
|
|
|
In the ALSA world, 1 frame = channels * samples-size.
|
|
|
For conversion between frames and bytes, you can use the
|
|
|
- helper functions, <function>frames_to_bytes()</function> and
|
|
|
- <function>bytes_to_frames()</function>.
|
|
|
+ <function>frames_to_bytes()</function> and
|
|
|
+ <function>bytes_to_frames()</function> helper functions.
|
|
|
<informalexample>
|
|
|
<programlisting>
|
|
|
<![CDATA[
|
|
|
@@ -2515,7 +2515,7 @@ struct _snd_pcm_runtime {
|
|
|
<structfield>dma_area</structfield> is necessary when the
|
|
|
buffer is mmapped. If your driver doesn't support mmap, this
|
|
|
field is not necessary. <structfield>dma_addr</structfield>
|
|
|
- is also not mandatory. You can use
|
|
|
+ is also optional. You can use
|
|
|
<structfield>dma_private</structfield> as you like, too.
|
|
|
</para>
|
|
|
</section>
|
|
|
@@ -2524,14 +2524,14 @@ struct _snd_pcm_runtime {
|
|
|
<title>Running Status</title>
|
|
|
<para>
|
|
|
The running status can be referred via <constant>runtime->status</constant>.
|
|
|
- This is the pointer to struct <structname>snd_pcm_mmap_status</structname>
|
|
|
+ This is the pointer to the struct <structname>snd_pcm_mmap_status</structname>
|
|
|
record. For example, you can get the current DMA hardware
|
|
|
pointer via <constant>runtime->status->hw_ptr</constant>.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
The DMA application pointer can be referred via
|
|
|
- <constant>runtime->control</constant>, which points
|
|
|
+ <constant>runtime->control</constant>, which points to the
|
|
|
struct <structname>snd_pcm_mmap_control</structname> record.
|
|
|
However, accessing directly to this value is not recommended.
|
|
|
</para>
|
|
|
@@ -2542,14 +2542,14 @@ struct _snd_pcm_runtime {
|
|
|
<para>
|
|
|
You can allocate a record for the substream and store it in
|
|
|
<constant>runtime->private_data</constant>. Usually, this
|
|
|
- done in
|
|
|
+ is done in
|
|
|
<link linkend="pcm-interface-operators-open-callback"><citetitle>
|
|
|
the open callback</citetitle></link>.
|
|
|
Don't mix this with <constant>pcm->private_data</constant>.
|
|
|
- The <constant>pcm->private_data</constant> usually points the
|
|
|
+ The <constant>pcm->private_data</constant> usually points to the
|
|
|
chip instance assigned statically at the creation of PCM, while the
|
|
|
- <constant>runtime->private_data</constant> points a dynamic
|
|
|
- data created at the PCM open callback.
|
|
|
+ <constant>runtime->private_data</constant> points to a dynamic
|
|
|
+ data structure created at the PCM open callback.
|
|
|
|
|
|
<informalexample>
|
|
|
<programlisting>
|
|
|
@@ -2579,7 +2579,7 @@ struct _snd_pcm_runtime {
|
|
|
<para>
|
|
|
The field <structfield>transfer_ack_begin</structfield> and
|
|
|
<structfield>transfer_ack_end</structfield> are called at
|
|
|
- the beginning and the end of
|
|
|
+ the beginning and at the end of
|
|
|
<function>snd_pcm_period_elapsed()</function>, respectively.
|
|
|
</para>
|
|
|
</section>
|
|
|
@@ -2589,17 +2589,18 @@ struct _snd_pcm_runtime {
|
|
|
<section id="pcm-interface-operators">
|
|
|
<title>Operators</title>
|
|
|
<para>
|
|
|
- OK, now let me explain the detail of each pcm callback
|
|
|
+ OK, now let me give details about each pcm callback
|
|
|
(<parameter>ops</parameter>). In general, every callback must
|
|
|
- return 0 if successful, or a negative number with the error
|
|
|
- number such as <constant>-EINVAL</constant> at any
|
|
|
- error.
|
|
|
+ return 0 if successful, or a negative error number
|
|
|
+ such as <constant>-EINVAL</constant>. To choose an appropriate
|
|
|
+ error number, it is advised to check what value other parts of
|
|
|
+ the kernel return when the same kind of request fails.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
The callback function takes at least the argument with
|
|
|
- <structname>snd_pcm_substream</structname> pointer. For retrieving the
|
|
|
- chip record from the given substream instance, you can use the
|
|
|
+ <structname>snd_pcm_substream</structname> pointer. To retrieve
|
|
|
+ the chip record from the given substream instance, you can use the
|
|
|
following macro.
|
|
|
|
|
|
<informalexample>
|
|
|
@@ -2616,7 +2617,7 @@ struct _snd_pcm_runtime {
|
|
|
The macro reads <constant>substream->private_data</constant>,
|
|
|
which is a copy of <constant>pcm->private_data</constant>.
|
|
|
You can override the former if you need to assign different data
|
|
|
- records per PCM substream. For example, cmi8330 driver assigns
|
|
|
+ records per PCM substream. For example, the cmi8330 driver assigns
|
|
|
different private_data for playback and capture directions,
|
|
|
because it uses two different codecs (SB- and AD-compatible) for
|
|
|
different directions.
|
|
|
@@ -2709,7 +2710,7 @@ struct _snd_pcm_runtime {
|
|
|
<section id="pcm-interface-operators-ioctl-callback">
|
|
|
<title>ioctl callback</title>
|
|
|
<para>
|
|
|
- This is used for any special action to pcm ioctls. But
|
|
|
+ This is used for any special call to pcm ioctls. But
|
|
|
usually you can pass a generic ioctl callback,
|
|
|
<function>snd_pcm_lib_ioctl</function>.
|
|
|
</para>
|
|
|
@@ -2726,9 +2727,6 @@ struct _snd_pcm_runtime {
|
|
|
]]>
|
|
|
</programlisting>
|
|
|
</informalexample>
|
|
|
-
|
|
|
- This and <structfield>hw_free</structfield> callbacks exist
|
|
|
- only on ALSA 0.9.x.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
@@ -2740,13 +2738,13 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- Many hardware set-up should be done in this callback,
|
|
|
+ Many hardware setups should be done in this callback,
|
|
|
including the allocation of buffers.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
Parameters to be initialized are retrieved by
|
|
|
- <function>params_xxx()</function> macros. For allocating a
|
|
|
+ <function>params_xxx()</function> macros. To allocate
|
|
|
buffer, you can call a helper function,
|
|
|
|
|
|
<informalexample>
|
|
|
@@ -2772,8 +2770,8 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- Thus, you need to take care not to allocate the same buffers
|
|
|
- many times, which will lead to memory leak! Calling the
|
|
|
+ Thus, you need to be careful not to allocate the same buffers
|
|
|
+ many times, which will lead to memory leaks! Calling the
|
|
|
helper function above many times is OK. It will release the
|
|
|
previous buffer automatically when it was already allocated.
|
|
|
</para>
|
|
|
@@ -2782,7 +2780,7 @@ struct _snd_pcm_runtime {
|
|
|
Another note is that this callback is non-atomic
|
|
|
(schedulable). This is important, because the
|
|
|
<structfield>trigger</structfield> callback
|
|
|
- is atomic (non-schedulable). That is, mutex or any
|
|
|
+ is atomic (non-schedulable). That is, mutexes or any
|
|
|
schedule-related functions are not available in
|
|
|
<structfield>trigger</structfield> callback.
|
|
|
Please see the subsection
|
|
|
@@ -2843,15 +2841,15 @@ struct _snd_pcm_runtime {
|
|
|
<quote>prepared</quote>. You can set the format type, sample
|
|
|
rate, etc. here. The difference from
|
|
|
<structfield>hw_params</structfield> is that the
|
|
|
- <structfield>prepare</structfield> callback will be called at each
|
|
|
+ <structfield>prepare</structfield> callback will be called each
|
|
|
time
|
|
|
<function>snd_pcm_prepare()</function> is called, i.e. when
|
|
|
- recovered after underruns, etc.
|
|
|
+ recovering after underruns, etc.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- Note that this callback became non-atomic since the recent version.
|
|
|
- You can use schedule-related functions safely in this callback now.
|
|
|
+ Note that this callback is now non-atomic.
|
|
|
+ You can use schedule-related functions safely in this callback.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
@@ -2871,7 +2869,7 @@ struct _snd_pcm_runtime {
|
|
|
|
|
|
<para>
|
|
|
Be careful that this callback will be called many times at
|
|
|
- each set up, too.
|
|
|
+ each setup, too.
|
|
|
</para>
|
|
|
</section>
|
|
|
|
|
|
@@ -2893,7 +2891,7 @@ struct _snd_pcm_runtime {
|
|
|
Which action is specified in the second argument,
|
|
|
<constant>SNDRV_PCM_TRIGGER_XXX</constant> in
|
|
|
<filename><sound/pcm.h></filename>. At least,
|
|
|
- <constant>START</constant> and <constant>STOP</constant>
|
|
|
+ the <constant>START</constant> and <constant>STOP</constant>
|
|
|
commands must be defined in this callback.
|
|
|
|
|
|
<informalexample>
|
|
|
@@ -2915,8 +2913,8 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- When the pcm supports the pause operation (given in info
|
|
|
- field of the hardware table), <constant>PAUSE_PUSE</constant>
|
|
|
+ When the pcm supports the pause operation (given in the info
|
|
|
+ field of the hardware table), the <constant>PAUSE_PUSE</constant>
|
|
|
and <constant>PAUSE_RELEASE</constant> commands must be
|
|
|
handled here, too. The former is the command to pause the pcm,
|
|
|
and the latter to restart the pcm again.
|
|
|
@@ -2925,21 +2923,21 @@ struct _snd_pcm_runtime {
|
|
|
<para>
|
|
|
When the pcm supports the suspend/resume operation,
|
|
|
regardless of full or partial suspend/resume support,
|
|
|
- <constant>SUSPEND</constant> and <constant>RESUME</constant>
|
|
|
+ the <constant>SUSPEND</constant> and <constant>RESUME</constant>
|
|
|
commands must be handled, too.
|
|
|
These commands are issued when the power-management status is
|
|
|
changed. Obviously, the <constant>SUSPEND</constant> and
|
|
|
- <constant>RESUME</constant>
|
|
|
- do suspend and resume of the pcm substream, and usually, they
|
|
|
- are identical with <constant>STOP</constant> and
|
|
|
+ <constant>RESUME</constant> commands
|
|
|
+ suspend and resume the pcm substream, and usually, they
|
|
|
+ are identical to the <constant>STOP</constant> and
|
|
|
<constant>START</constant> commands, respectively.
|
|
|
- See <link linkend="power-management"><citetitle>
|
|
|
+ See the <link linkend="power-management"><citetitle>
|
|
|
Power Management</citetitle></link> section for details.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
As mentioned, this callback is atomic. You cannot call
|
|
|
- the function going to sleep.
|
|
|
+ functions which may sleep.
|
|
|
The trigger callback should be as minimal as possible,
|
|
|
just really triggering the DMA. The other stuff should be
|
|
|
initialized hw_params and prepare callbacks properly
|
|
|
@@ -2960,8 +2958,8 @@ struct _snd_pcm_runtime {
|
|
|
|
|
|
This callback is called when the PCM middle layer inquires
|
|
|
the current hardware position on the buffer. The position must
|
|
|
- be returned in frames (which was in bytes on ALSA 0.5.x),
|
|
|
- ranged from 0 to buffer_size - 1.
|
|
|
+ be returned in frames,
|
|
|
+ ranging from 0 to buffer_size - 1.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
@@ -2983,7 +2981,7 @@ struct _snd_pcm_runtime {
|
|
|
<para>
|
|
|
These callbacks are not mandatory, and can be omitted in
|
|
|
most cases. These callbacks are used when the hardware buffer
|
|
|
- cannot be on the normal memory space. Some chips have their
|
|
|
+ cannot be in the normal memory space. Some chips have their
|
|
|
own buffer on the hardware which is not mappable. In such a
|
|
|
case, you have to transfer the data manually from the memory
|
|
|
buffer to the hardware buffer. Or, if the buffer is
|
|
|
@@ -3018,8 +3016,8 @@ struct _snd_pcm_runtime {
|
|
|
<title>page callback</title>
|
|
|
|
|
|
<para>
|
|
|
- This callback is also not mandatory. This callback is used
|
|
|
- mainly for the non-contiguous buffer. The mmap calls this
|
|
|
+ This callback is optional too. This callback is used
|
|
|
+ mainly for non-contiguous buffers. The mmap calls this
|
|
|
callback to get the page address. Some examples will be
|
|
|
explained in the later section <link
|
|
|
linkend="buffer-and-memory"><citetitle>Buffer and Memory
|
|
|
@@ -3035,7 +3033,7 @@ struct _snd_pcm_runtime {
|
|
|
role of PCM interrupt handler in the sound driver is to update
|
|
|
the buffer position and to tell the PCM middle layer when the
|
|
|
buffer position goes across the prescribed period size. To
|
|
|
- inform this, call <function>snd_pcm_period_elapsed()</function>
|
|
|
+ inform this, call the <function>snd_pcm_period_elapsed()</function>
|
|
|
function.
|
|
|
</para>
|
|
|
|
|
|
@@ -3072,7 +3070,7 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- A typical coding would be like:
|
|
|
+ Typical code would be like:
|
|
|
|
|
|
<example>
|
|
|
<title>Interrupt Handler Case #1</title>
|
|
|
@@ -3101,21 +3099,21 @@ struct _snd_pcm_runtime {
|
|
|
</section>
|
|
|
|
|
|
<section id="pcm-interface-interrupt-handler-timer">
|
|
|
- <title>High-frequent timer interrupts</title>
|
|
|
+ <title>High frequency timer interrupts</title>
|
|
|
<para>
|
|
|
- This is the case when the hardware doesn't generate interrupts
|
|
|
- at the period boundary but do timer-interrupts at the fixed
|
|
|
+ This happense when the hardware doesn't generate interrupts
|
|
|
+ at the period boundary but issues timer interrupts at a fixed
|
|
|
timer rate (e.g. es1968 or ymfpci drivers).
|
|
|
In this case, you need to check the current hardware
|
|
|
- position and accumulates the processed sample length at each
|
|
|
- interrupt. When the accumulated size overcomes the period
|
|
|
+ position and accumulate the processed sample length at each
|
|
|
+ interrupt. When the accumulated size exceeds the period
|
|
|
size, call
|
|
|
<function>snd_pcm_period_elapsed()</function> and reset the
|
|
|
accumulator.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- A typical coding would be like the following.
|
|
|
+ Typical code would be like the following.
|
|
|
|
|
|
<example>
|
|
|
<title>Interrupt Handler Case #2</title>
|
|
|
@@ -3178,32 +3176,33 @@ struct _snd_pcm_runtime {
|
|
|
<section id="pcm-interface-atomicity">
|
|
|
<title>Atomicity</title>
|
|
|
<para>
|
|
|
- One of the most important (and thus difficult to debug) problem
|
|
|
- on the kernel programming is the race condition.
|
|
|
- On linux kernel, usually it's solved via spin-locks or
|
|
|
- semaphores. In general, if the race condition may
|
|
|
- happen in the interrupt handler, it's handled as atomic, and you
|
|
|
- have to use spinlock for protecting the critical session. If it
|
|
|
- never happens in the interrupt and it may take relatively long
|
|
|
- time, you should use semaphore.
|
|
|
+ One of the most important (and thus difficult to debug) problems
|
|
|
+ in kernel programming are race conditions.
|
|
|
+ In the Linux kernel, they are usually avoided via spin-locks, mutexes
|
|
|
+ or semaphores. In general, if a race condition can happen
|
|
|
+ in an interrupt handler, it has to be managed atomically, and you
|
|
|
+ have to use a spinlock to protect the critical session. If the
|
|
|
+ critical section is not in interrupt handler code and
|
|
|
+ if taking a relatively long time to execute is acceptable, you
|
|
|
+ should use mutexes or semaphores instead.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
As already seen, some pcm callbacks are atomic and some are
|
|
|
- not. For example, <parameter>hw_params</parameter> callback is
|
|
|
+ not. For example, the <parameter>hw_params</parameter> callback is
|
|
|
non-atomic, while <parameter>trigger</parameter> callback is
|
|
|
atomic. This means, the latter is called already in a spinlock
|
|
|
held by the PCM middle layer. Please take this atomicity into
|
|
|
- account when you use a spinlock or a semaphore in the callbacks.
|
|
|
+ account when you choose a locking scheme in the callbacks.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
In the atomic callbacks, you cannot use functions which may call
|
|
|
<function>schedule</function> or go to
|
|
|
- <function>sleep</function>. The semaphore and mutex do sleep,
|
|
|
+ <function>sleep</function>. Semaphores and mutexes can sleep,
|
|
|
and hence they cannot be used inside the atomic callbacks
|
|
|
(e.g. <parameter>trigger</parameter> callback).
|
|
|
- For taking a certain delay in such a callback, please use
|
|
|
+ To implement some delay in such a callback, please use
|
|
|
<function>udelay()</function> or <function>mdelay()</function>.
|
|
|
</para>
|
|
|
|
|
|
@@ -3257,7 +3256,7 @@ struct _snd_pcm_runtime {
|
|
|
|
|
|
<para>
|
|
|
There are many different constraints.
|
|
|
- Look in <filename>sound/pcm.h</filename> for a complete list.
|
|
|
+ Look at <filename>sound/pcm.h</filename> for a complete list.
|
|
|
You can even define your own constraint rules.
|
|
|
For example, let's suppose my_chip can manage a substream of 1 channel
|
|
|
if and only if the format is S16_LE, otherwise it supports any format
|
|
|
@@ -3346,7 +3345,7 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- I won't explain more details here, rather I
|
|
|
+ I won't give more details here, rather I
|
|
|
would like to say, <quote>Luke, use the source.</quote>
|
|
|
</para>
|
|
|
</section>
|
|
|
@@ -3364,10 +3363,9 @@ struct _snd_pcm_runtime {
|
|
|
<title>General</title>
|
|
|
<para>
|
|
|
The control interface is used widely for many switches,
|
|
|
- sliders, etc. which are accessed from the user-space. Its most
|
|
|
- important use is the mixer interface. In other words, on ALSA
|
|
|
- 0.9.x, all the mixer stuff is implemented on the control kernel
|
|
|
- API (while there was an independent mixer kernel API on 0.5.x).
|
|
|
+ sliders, etc. which are accessed from user-space. Its most
|
|
|
+ important use is the mixer interface. In other words, since ALSA
|
|
|
+ 0.9.x, all the mixer stuff is implemented on the control kernel API.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
@@ -3379,14 +3377,15 @@ struct _snd_pcm_runtime {
|
|
|
<para>
|
|
|
The control API is defined in
|
|
|
<filename><sound/control.h></filename>.
|
|
|
- Include this file if you add your own controls.
|
|
|
+ Include this file if you want to add your own controls.
|
|
|
</para>
|
|
|
</section>
|
|
|
|
|
|
<section id="control-interface-definition">
|
|
|
<title>Definition of Controls</title>
|
|
|
<para>
|
|
|
- For creating a new control, you need to define the three
|
|
|
+ To create a new control, you need to define the
|
|
|
+ following three
|
|
|
callbacks: <structfield>info</structfield>,
|
|
|
<structfield>get</structfield> and
|
|
|
<structfield>put</structfield>. Then, define a
|
|
|
@@ -3414,13 +3413,13 @@ struct _snd_pcm_runtime {
|
|
|
<para>
|
|
|
Most likely the control is created via
|
|
|
<function>snd_ctl_new1()</function>, and in such a case, you can
|
|
|
- add <parameter>__devinitdata</parameter> prefix to the
|
|
|
- definition like above.
|
|
|
+ add the <parameter>__devinitdata</parameter> prefix to the
|
|
|
+ definition as above.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- The <structfield>iface</structfield> field specifies the type of
|
|
|
- the control, <constant>SNDRV_CTL_ELEM_IFACE_XXX</constant>, which
|
|
|
+ The <structfield>iface</structfield> field specifies the control
|
|
|
+ type, <constant>SNDRV_CTL_ELEM_IFACE_XXX</constant>, which
|
|
|
is usually <constant>MIXER</constant>.
|
|
|
Use <constant>CARD</constant> for global controls that are not
|
|
|
logically part of the mixer.
|
|
|
@@ -3435,12 +3434,11 @@ struct _snd_pcm_runtime {
|
|
|
|
|
|
<para>
|
|
|
The <structfield>name</structfield> is the name identifier
|
|
|
- string. On ALSA 0.9.x, the control name is very important,
|
|
|
+ string. Since ALSA 0.9.x, the control name is very important,
|
|
|
because its role is classified from its name. There are
|
|
|
pre-defined standard control names. The details are described in
|
|
|
- the subsection
|
|
|
- <link linkend="control-interface-control-names"><citetitle>
|
|
|
- Control Names</citetitle></link>.
|
|
|
+ the <link linkend="control-interface-control-names"><citetitle>
|
|
|
+ Control Names</citetitle></link> subsection.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
@@ -3456,15 +3454,15 @@ struct _snd_pcm_runtime {
|
|
|
The <structfield>access</structfield> field contains the access
|
|
|
type of this control. Give the combination of bit masks,
|
|
|
<constant>SNDRV_CTL_ELEM_ACCESS_XXX</constant>, there.
|
|
|
- The detailed will be explained in the subsection
|
|
|
- <link linkend="control-interface-access-flags"><citetitle>
|
|
|
- Access Flags</citetitle></link>.
|
|
|
+ The details will be explained in
|
|
|
+ the <link linkend="control-interface-access-flags"><citetitle>
|
|
|
+ Access Flags</citetitle></link> subsection.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
The <structfield>private_value</structfield> field contains
|
|
|
an arbitrary long integer value for this record. When using
|
|
|
- generic <structfield>info</structfield>,
|
|
|
+ the generic <structfield>info</structfield>,
|
|
|
<structfield>get</structfield> and
|
|
|
<structfield>put</structfield> callbacks, you can pass a value
|
|
|
through this field. If several small numbers are necessary, you can
|
|
|
@@ -3489,7 +3487,7 @@ struct _snd_pcm_runtime {
|
|
|
<section id="control-interface-control-names">
|
|
|
<title>Control Names</title>
|
|
|
<para>
|
|
|
- There are some standards for defining the control names. A
|
|
|
+ There are some standards to define the control names. A
|
|
|
control is usually defined from the three parts as
|
|
|
<quote>SOURCE DIRECTION FUNCTION</quote>.
|
|
|
</para>
|
|
|
@@ -3497,7 +3495,7 @@ struct _snd_pcm_runtime {
|
|
|
<para>
|
|
|
The first, <constant>SOURCE</constant>, specifies the source
|
|
|
of the control, and is a string such as <quote>Master</quote>,
|
|
|
- <quote>PCM</quote>, <quote>CD</quote> or
|
|
|
+ <quote>PCM</quote>, <quote>CD</quote> and
|
|
|
<quote>Line</quote>. There are many pre-defined sources.
|
|
|
</para>
|
|
|
|
|
|
@@ -3575,22 +3573,22 @@ struct _snd_pcm_runtime {
|
|
|
<title>Access Flags</title>
|
|
|
|
|
|
<para>
|
|
|
- The access flag is the bit-flags which specifies the access type
|
|
|
+ The access flag is the bitmask which specifies the access type
|
|
|
of the given control. The default access type is
|
|
|
<constant>SNDRV_CTL_ELEM_ACCESS_READWRITE</constant>,
|
|
|
which means both read and write are allowed to this control.
|
|
|
When the access flag is omitted (i.e. = 0), it is
|
|
|
- regarded as <constant>READWRITE</constant> access as default.
|
|
|
+ considered as <constant>READWRITE</constant> access as default.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
When the control is read-only, pass
|
|
|
<constant>SNDRV_CTL_ELEM_ACCESS_READ</constant> instead.
|
|
|
In this case, you don't have to define
|
|
|
- <structfield>put</structfield> callback.
|
|
|
+ the <structfield>put</structfield> callback.
|
|
|
Similarly, when the control is write-only (although it's a rare
|
|
|
- case), you can use <constant>WRITE</constant> flag instead, and
|
|
|
- you don't need <structfield>get</structfield> callback.
|
|
|
+ case), you can use the <constant>WRITE</constant> flag instead, and
|
|
|
+ you don't need the <structfield>get</structfield> callback.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
@@ -3598,15 +3596,15 @@ struct _snd_pcm_runtime {
|
|
|
<constant>VOLATILE</constant> flag should be given. This means
|
|
|
that the control may be changed without
|
|
|
<link linkend="control-interface-change-notification"><citetitle>
|
|
|
- notification</citetitle></link>. Applications should poll such
|
|
|
+ notification</citetitle></link>. Applications should poll such
|
|
|
a control constantly.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
When the control is inactive, set
|
|
|
- <constant>INACTIVE</constant> flag, too.
|
|
|
+ the <constant>INACTIVE</constant> flag, too.
|
|
|
There are <constant>LOCK</constant> and
|
|
|
- <constant>OWNER</constant> flags for changing the write
|
|
|
+ <constant>OWNER</constant> flags to change the write
|
|
|
permissions.
|
|
|
</para>
|
|
|
|
|
|
@@ -3619,10 +3617,10 @@ struct _snd_pcm_runtime {
|
|
|
<title>info callback</title>
|
|
|
<para>
|
|
|
The <structfield>info</structfield> callback is used to get
|
|
|
- the detailed information of this control. This must store the
|
|
|
+ detailed information on this control. This must store the
|
|
|
values of the given struct <structname>snd_ctl_elem_info</structname>
|
|
|
object. For example, for a boolean control with a single
|
|
|
- element will be:
|
|
|
+ element:
|
|
|
|
|
|
<example>
|
|
|
<title>Example of info callback</title>
|
|
|
@@ -3653,7 +3651,7 @@ struct _snd_pcm_runtime {
|
|
|
volume would have count = 2. The
|
|
|
<structfield>value</structfield> field is a union, and
|
|
|
the values stored are depending on the type. The boolean and
|
|
|
- integer are identical.
|
|
|
+ integer types are identical.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
@@ -3684,7 +3682,7 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- Some common info callbacks are prepared for easy use:
|
|
|
+ Some common info callbacks are available for your convenience:
|
|
|
<function>snd_ctl_boolean_mono_info()</function> and
|
|
|
<function>snd_ctl_boolean_stereo_info()</function>.
|
|
|
Obviously, the former is an info callback for a mono channel
|
|
|
@@ -3699,7 +3697,7 @@ struct _snd_pcm_runtime {
|
|
|
|
|
|
<para>
|
|
|
This callback is used to read the current value of the
|
|
|
- control and to return to the user-space.
|
|
|
+ control and to return to user-space.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
@@ -3722,11 +3720,11 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- The <structfield>value</structfield> field is depending on
|
|
|
- the type of control as well as on info callback. For example,
|
|
|
+ The <structfield>value</structfield> field depends on
|
|
|
+ the type of control as well as on the info callback. For example,
|
|
|
the sb driver uses this field to store the register offset,
|
|
|
the bit-shift and the bit-mask. The
|
|
|
- <structfield>private_value</structfield> is set like
|
|
|
+ <structfield>private_value</structfield> field is set as follows:
|
|
|
<informalexample>
|
|
|
<programlisting>
|
|
|
<![CDATA[
|
|
|
@@ -3752,7 +3750,8 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- In <structfield>get</structfield> callback, you have to fill all the elements if the
|
|
|
+ In the <structfield>get</structfield> callback,
|
|
|
+ you have to fill all the elements if the
|
|
|
control has more than one elements,
|
|
|
i.e. <structfield>count</structfield> > 1.
|
|
|
In the example above, we filled only one element
|
|
|
@@ -3765,7 +3764,7 @@ struct _snd_pcm_runtime {
|
|
|
<title>put callback</title>
|
|
|
|
|
|
<para>
|
|
|
- This callback is used to write a value from the user-space.
|
|
|
+ This callback is used to write a value from user-space.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
@@ -3799,7 +3798,7 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- Like <structfield>get</structfield> callback,
|
|
|
+ As in the <structfield>get</structfield> callback,
|
|
|
when the control has more than one elements,
|
|
|
all elements must be evaluated in this callback, too.
|
|
|
</para>
|
|
|
@@ -3817,7 +3816,7 @@ struct _snd_pcm_runtime {
|
|
|
<title>Constructor</title>
|
|
|
<para>
|
|
|
When everything is ready, finally we can create a new
|
|
|
- control. For creating a control, there are two functions to be
|
|
|
+ control. To create a control, there are two functions to be
|
|
|
called, <function>snd_ctl_new1()</function> and
|
|
|
<function>snd_ctl_add()</function>.
|
|
|
</para>
|
|
|
@@ -3839,14 +3838,14 @@ struct _snd_pcm_runtime {
|
|
|
struct <structname>snd_kcontrol_new</structname> object defined above, and chip
|
|
|
is the object pointer to be passed to
|
|
|
kcontrol->private_data
|
|
|
- which can be referred in callbacks.
|
|
|
+ which can be referred to in callbacks.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
<function>snd_ctl_new1()</function> allocates a new
|
|
|
<structname>snd_kcontrol</structname> instance (that's why the definition
|
|
|
of <parameter>my_control</parameter> can be with
|
|
|
- <parameter>__devinitdata</parameter>
|
|
|
+ the <parameter>__devinitdata</parameter>
|
|
|
prefix), and <function>snd_ctl_add</function> assigns the given
|
|
|
control component to the card.
|
|
|
</para>
|
|
|
@@ -3941,7 +3940,7 @@ struct _snd_pcm_runtime {
|
|
|
<title>General</title>
|
|
|
<para>
|
|
|
The ALSA AC97 codec layer is a well-defined one, and you don't
|
|
|
- have to write many codes to control it. Only low-level control
|
|
|
+ have to write much code to control it. Only low-level control
|
|
|
routines are necessary. The AC97 codec API is defined in
|
|
|
<filename><sound/ac97_codec.h></filename>.
|
|
|
</para>
|
|
|
@@ -4004,7 +4003,7 @@ struct _snd_pcm_runtime {
|
|
|
<section id="api-ac97-constructor">
|
|
|
<title>Constructor</title>
|
|
|
<para>
|
|
|
- For creating an ac97 instance, first call <function>snd_ac97_bus</function>
|
|
|
+ To create an ac97 instance, first call <function>snd_ac97_bus</function>
|
|
|
with an <type>ac97_bus_ops_t</type> record with callback functions.
|
|
|
|
|
|
<informalexample>
|
|
|
@@ -4042,12 +4041,12 @@ struct _snd_pcm_runtime {
|
|
|
</programlisting>
|
|
|
</informalexample>
|
|
|
|
|
|
- where chip->ac97 is the pointer of a newly created
|
|
|
+ where chip->ac97 is a pointer to a newly created
|
|
|
<type>ac97_t</type> instance.
|
|
|
In this case, the chip pointer is set as the private data, so that
|
|
|
the read/write callback functions can refer to this chip instance.
|
|
|
This instance is not necessarily stored in the chip
|
|
|
- record. When you need to change the register values from the
|
|
|
+ record. If you need to change the register values from the
|
|
|
driver, or need the suspend/resume of ac97 codecs, keep this
|
|
|
pointer to pass to the corresponding functions.
|
|
|
</para>
|
|
|
@@ -4098,7 +4097,7 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- These callbacks are non-atomic like the callbacks of control API.
|
|
|
+ These callbacks are non-atomic like the control API callbacks.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
@@ -4110,14 +4109,14 @@ struct _snd_pcm_runtime {
|
|
|
|
|
|
<para>
|
|
|
The <structfield>reset</structfield> callback is used to reset
|
|
|
- the codec. If the chip requires a special way of reset, you can
|
|
|
+ the codec. If the chip requires a special kind of reset, you can
|
|
|
define this callback.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- The <structfield>wait</structfield> callback is used for a
|
|
|
- certain wait at the standard initialization of the codec. If the
|
|
|
- chip requires the extra wait-time, define this callback.
|
|
|
+ The <structfield>wait</structfield> callback is used to
|
|
|
+ add some waiting time in the standard initialization of the codec. If the
|
|
|
+ chip requires the extra waiting time, define this callback.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
@@ -4172,7 +4171,7 @@ struct _snd_pcm_runtime {
|
|
|
|
|
|
<para>
|
|
|
<function>snd_ac97_update_bits()</function> is used to update
|
|
|
- some bits of the given register.
|
|
|
+ some bits in the given register.
|
|
|
|
|
|
<informalexample>
|
|
|
<programlisting>
|
|
|
@@ -4185,7 +4184,7 @@ struct _snd_pcm_runtime {
|
|
|
|
|
|
<para>
|
|
|
Also, there is a function to change the sample rate (of a
|
|
|
- certain register such as
|
|
|
+ given register such as
|
|
|
<constant>AC97_PCM_FRONT_DAC_RATE</constant>) when VRA or
|
|
|
DRA is supported by the codec:
|
|
|
<function>snd_ac97_set_rate()</function>.
|
|
|
@@ -4200,11 +4199,11 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- The following registers are available for setting the rate:
|
|
|
+ The following registers are available to set the rate:
|
|
|
<constant>AC97_PCM_MIC_ADC_RATE</constant>,
|
|
|
<constant>AC97_PCM_FRONT_DAC_RATE</constant>,
|
|
|
<constant>AC97_PCM_LR_ADC_RATE</constant>,
|
|
|
- <constant>AC97_SPDIF</constant>. When the
|
|
|
+ <constant>AC97_SPDIF</constant>. When
|
|
|
<constant>AC97_SPDIF</constant> is specified, the register is
|
|
|
not really changed but the corresponding IEC958 status bits will
|
|
|
be updated.
|
|
|
@@ -4214,12 +4213,11 @@ struct _snd_pcm_runtime {
|
|
|
<section id="api-ac97-clock-adjustment">
|
|
|
<title>Clock Adjustment</title>
|
|
|
<para>
|
|
|
- On some chip, the clock of the codec isn't 48000 but using a
|
|
|
+ In some chips, the clock of the codec isn't 48000 but using a
|
|
|
PCI clock (to save a quartz!). In this case, change the field
|
|
|
bus->clock to the corresponding
|
|
|
value. For example, intel8x0
|
|
|
- and es1968 drivers have the auto-measurement function of the
|
|
|
- clock.
|
|
|
+ and es1968 drivers have their own function to read from the clock.
|
|
|
</para>
|
|
|
</section>
|
|
|
|
|
|
@@ -4239,15 +4237,13 @@ struct _snd_pcm_runtime {
|
|
|
When there are several codecs on the same card, you need to
|
|
|
call <function>snd_ac97_mixer()</function> multiple times with
|
|
|
ac97.num=1 or greater. The <structfield>num</structfield> field
|
|
|
- specifies the codec
|
|
|
- number.
|
|
|
+ specifies the codec number.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- If you have set up multiple codecs, you need to either write
|
|
|
+ If you set up multiple codecs, you either need to write
|
|
|
different callbacks for each codec or check
|
|
|
- ac97->num in the
|
|
|
- callback routines.
|
|
|
+ ac97->num in the callback routines.
|
|
|
</para>
|
|
|
</section>
|
|
|
|
|
|
@@ -4271,7 +4267,7 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- Some soundchips have similar but a little bit different
|
|
|
+ Some soundchips have a similar but slightly different
|
|
|
implementation of mpu401 stuff. For example, emu10k1 has its own
|
|
|
mpu401 routines.
|
|
|
</para>
|
|
|
@@ -4280,7 +4276,7 @@ struct _snd_pcm_runtime {
|
|
|
<section id="midi-interface-constructor">
|
|
|
<title>Constructor</title>
|
|
|
<para>
|
|
|
- For creating a rawmidi object, call
|
|
|
+ To create a rawmidi object, call
|
|
|
<function>snd_mpu401_uart_new()</function>.
|
|
|
|
|
|
<informalexample>
|
|
|
@@ -4307,25 +4303,24 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- The 4th argument is the i/o port address. Many
|
|
|
- backward-compatible MPU401 has an i/o port such as 0x330. Or, it
|
|
|
- might be a part of its own PCI i/o region. It depends on the
|
|
|
+ The 4th argument is the I/O port address. Many
|
|
|
+ backward-compatible MPU401 have an I/O port such as 0x330. Or, it
|
|
|
+ might be a part of its own PCI I/O region. It depends on the
|
|
|
chip design.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- The 5th argument is bitflags for additional information.
|
|
|
- When the i/o port address above is a part of the PCI i/o
|
|
|
- region, the MPU401 i/o port might have been already allocated
|
|
|
+ The 5th argument is a bitflag for additional information.
|
|
|
+ When the I/O port address above is part of the PCI I/O
|
|
|
+ region, the MPU401 I/O port might have been already allocated
|
|
|
(reserved) by the driver itself. In such a case, pass a bit flag
|
|
|
<constant>MPU401_INFO_INTEGRATED</constant>,
|
|
|
- and
|
|
|
- the mpu401-uart layer will allocate the i/o ports by itself.
|
|
|
+ and the mpu401-uart layer will allocate the I/O ports by itself.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
When the controller supports only the input or output MIDI stream,
|
|
|
- pass <constant>MPU401_INFO_INPUT</constant> or
|
|
|
+ pass the <constant>MPU401_INFO_INPUT</constant> or
|
|
|
<constant>MPU401_INFO_OUTPUT</constant> bitflag, respectively.
|
|
|
Then the rawmidi instance is created as a single stream.
|
|
|
</para>
|
|
|
@@ -4333,7 +4328,7 @@ struct _snd_pcm_runtime {
|
|
|
<para>
|
|
|
<constant>MPU401_INFO_MMIO</constant> bitflag is used to change
|
|
|
the access method to MMIO (via readb and writeb) instead of
|
|
|
- iob and outb. In this case, you have to pass the iomapped address
|
|
|
+ iob and outb. In this case, you have to pass the iomapped address
|
|
|
to <function>snd_mpu401_uart_new()</function>.
|
|
|
</para>
|
|
|
|
|
|
@@ -4341,7 +4336,7 @@ struct _snd_pcm_runtime {
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When <constant>MPU401_INFO_TX_IRQ</constant> is set, the output
|
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|
stream isn't checked in the default interrupt handler. The driver
|
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|
needs to call <function>snd_mpu401_uart_interrupt_tx()</function>
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- by itself to start processing the output stream in irq handler.
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+ by itself to start processing the output stream in the irq handler.
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</para>
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<para>
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@@ -4381,7 +4376,7 @@ struct _snd_pcm_runtime {
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(<parameter>irq_flags</parameter>). Otherwise, pass the flags
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|
for irq allocation
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(<constant>SA_XXX</constant> bits) to it, and the irq will be
|
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|
- reserved by the mpu401-uart layer. If the card doesn't generates
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+ reserved by the mpu401-uart layer. If the card doesn't generate
|
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|
UART interrupts, pass -1 as the irq number. Then a timer
|
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interrupt will be invoked for polling.
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</para>
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@@ -4392,8 +4387,8 @@ struct _snd_pcm_runtime {
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<para>
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|
When the interrupt is allocated in
|
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<function>snd_mpu401_uart_new()</function>, the private
|
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|
- interrupt handler is used, hence you don't have to do nothing
|
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|
- else than creating the mpu401 stuff. Otherwise, you have to call
|
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+ interrupt handler is used, hence you don't have anything else to do
|
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+ than creating the mpu401 stuff. Otherwise, you have to call
|
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<function>snd_mpu401_uart_interrupt()</function> explicitly when
|
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a UART interrupt is invoked and checked in your own interrupt
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handler.
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@@ -4480,8 +4475,8 @@ struct _snd_pcm_runtime {
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<para>
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The fourth and fifth arguments are the number of output and
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|
- input substreams, respectively, of this device. (A substream is
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- the equivalent of a MIDI port.)
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+ input substreams, respectively, of this device (a substream is
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+ the equivalent of a MIDI port).
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</para>
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<para>
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@@ -4498,7 +4493,7 @@ struct _snd_pcm_runtime {
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<para>
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|
After the rawmidi device is created, you need to set the
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|
operators (callbacks) for each substream. There are helper
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- functions to set the operators for all substream of a device:
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+ functions to set the operators for all the substreams of a device:
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<informalexample>
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<programlisting>
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<![CDATA[
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@@ -4528,8 +4523,8 @@ struct _snd_pcm_runtime {
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</para>
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<para>
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- If there is more than one substream, you should give each one a
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- unique name:
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+ If there are more than one substream, you should give a
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+ unique name to each of them:
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<informalexample>
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<programlisting>
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<![CDATA[
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@@ -4550,7 +4545,7 @@ struct _snd_pcm_runtime {
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<title>Callbacks</title>
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<para>
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- In all callbacks, the private data that you've set for the
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+ In all the callbacks, the private data that you've set for the
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|
rawmidi device can be accessed as
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|
substream->rmidi->private_data.
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|
<!-- <code> isn't available before DocBook 4.3 -->
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@@ -4583,8 +4578,8 @@ struct _snd_pcm_runtime {
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<para>
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This is called when a substream is opened.
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- You can initialize the hardware here, but you should not yet
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- start transmitting/receiving data.
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+ You can initialize the hardware here, but you shouldn't
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+ start transmitting/receiving data yet.
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</para>
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|
</section>
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@@ -4632,9 +4627,9 @@ struct _snd_pcm_runtime {
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To read data from the buffer, call
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<function>snd_rawmidi_transmit_peek</function>. It will
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return the number of bytes that have been read; this will be
|
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|
- less than the number of bytes requested when there is no more
|
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+ less than the number of bytes requested when there are no more
|
|
|
data in the buffer.
|
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|
- After the data has been transmitted successfully, call
|
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|
+ After the data have been transmitted successfully, call
|
|
|
<function>snd_rawmidi_transmit_ack</function> to remove the
|
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|
data from the substream buffer:
|
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|
<informalexample>
|
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|
@@ -4655,7 +4650,7 @@ struct _snd_pcm_runtime {
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<para>
|
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|
If you know beforehand that the hardware will accept data, you
|
|
|
can use the <function>snd_rawmidi_transmit</function> function
|
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- which reads some data and removes it from the buffer at once:
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+ which reads some data and removes them from the buffer at once:
|
|
|
<informalexample>
|
|
|
<programlisting>
|
|
|
<![CDATA[
|
|
|
@@ -4749,13 +4744,13 @@ struct _snd_pcm_runtime {
|
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|
|
|
|
<para>
|
|
|
This is only used with output substreams. This function should wait
|
|
|
- until all data read from the substream buffer has been transmitted.
|
|
|
+ until all data read from the substream buffer have been transmitted.
|
|
|
This ensures that the device can be closed and the driver unloaded
|
|
|
without losing data.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- This callback is optional. If you do not set
|
|
|
+ This callback is optional. If you do not set
|
|
|
<structfield>drain</structfield> in the struct snd_rawmidi_ops
|
|
|
structure, ALSA will simply wait for 50 milliseconds
|
|
|
instead.
|
|
|
@@ -4775,24 +4770,24 @@ struct _snd_pcm_runtime {
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|
|
<section id="misc-devices-opl3">
|
|
|
<title>FM OPL3</title>
|
|
|
<para>
|
|
|
- The FM OPL3 is still used on many chips (mainly for backward
|
|
|
+ The FM OPL3 is still used in many chips (mainly for backward
|
|
|
compatibility). ALSA has a nice OPL3 FM control layer, too. The
|
|
|
OPL3 API is defined in
|
|
|
<filename><sound/opl3.h></filename>.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- FM registers can be directly accessed through direct-FM API,
|
|
|
+ FM registers can be directly accessed through the direct-FM API,
|
|
|
defined in <filename><sound/asound_fm.h></filename>. In
|
|
|
ALSA native mode, FM registers are accessed through
|
|
|
- Hardware-Dependant Device direct-FM extension API, whereas in
|
|
|
- OSS compatible mode, FM registers can be accessed with OSS
|
|
|
- direct-FM compatible API on <filename>/dev/dmfmX</filename> device.
|
|
|
+ the Hardware-Dependant Device direct-FM extension API, whereas in
|
|
|
+ OSS compatible mode, FM registers can be accessed with the OSS
|
|
|
+ direct-FM compatible API in <filename>/dev/dmfmX</filename> device.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- For creating the OPL3 component, you have two functions to
|
|
|
- call. The first one is a constructor for <type>opl3_t</type>
|
|
|
+ To create the OPL3 component, you have two functions to
|
|
|
+ call. The first one is a constructor for the <type>opl3_t</type>
|
|
|
instance.
|
|
|
|
|
|
<informalexample>
|
|
|
@@ -4819,12 +4814,12 @@ struct _snd_pcm_runtime {
|
|
|
<para>
|
|
|
When the left and right ports have been already allocated by
|
|
|
the card driver, pass non-zero to the fifth argument
|
|
|
- (<parameter>integrated</parameter>). Otherwise, opl3 module will
|
|
|
+ (<parameter>integrated</parameter>). Otherwise, the opl3 module will
|
|
|
allocate the specified ports by itself.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- When the accessing to the hardware requires special method
|
|
|
+ When the accessing the hardware requires special method
|
|
|
instead of the standard I/O access, you can create opl3 instance
|
|
|
separately with <function>snd_opl3_new()</function>.
|
|
|
|
|
|
@@ -4845,13 +4840,13 @@ struct _snd_pcm_runtime {
|
|
|
access function, the private data and the destructor.
|
|
|
The l_port and r_port are not necessarily set. Only the
|
|
|
command must be set properly. You can retrieve the data
|
|
|
- from opl3->private_data field.
|
|
|
+ from the opl3->private_data field.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
After creating the opl3 instance via <function>snd_opl3_new()</function>,
|
|
|
call <function>snd_opl3_init()</function> to initialize the chip to the
|
|
|
- proper state. Note that <function>snd_opl3_create()</function> always
|
|
|
+ proper state. Note that <function>snd_opl3_create()</function> always
|
|
|
calls it internally.
|
|
|
</para>
|
|
|
|
|
|
@@ -4884,7 +4879,7 @@ struct _snd_pcm_runtime {
|
|
|
<section id="misc-devices-hardware-dependent">
|
|
|
<title>Hardware-Dependent Devices</title>
|
|
|
<para>
|
|
|
- Some chips need the access from the user-space for special
|
|
|
+ Some chips need user-space access for special
|
|
|
controls or for loading the micro code. In such a case, you can
|
|
|
create a hwdep (hardware-dependent) device. The hwdep API is
|
|
|
defined in <filename><sound/hwdep.h></filename>. You can
|
|
|
@@ -4893,7 +4888,7 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- Creation of the <type>hwdep</type> instance is done via
|
|
|
+ The creation of the <type>hwdep</type> instance is done via
|
|
|
<function>snd_hwdep_new()</function>.
|
|
|
|
|
|
<informalexample>
|
|
|
@@ -4912,8 +4907,8 @@ struct _snd_pcm_runtime {
|
|
|
You can then pass any pointer value to the
|
|
|
<parameter>private_data</parameter>.
|
|
|
If you assign a private data, you should define the
|
|
|
- destructor, too. The destructor function is set to
|
|
|
- <structfield>private_free</structfield> field.
|
|
|
+ destructor, too. The destructor function is set in
|
|
|
+ the <structfield>private_free</structfield> field.
|
|
|
|
|
|
<informalexample>
|
|
|
<programlisting>
|
|
|
@@ -4925,7 +4920,7 @@ struct _snd_pcm_runtime {
|
|
|
</programlisting>
|
|
|
</informalexample>
|
|
|
|
|
|
- and the implementation of destructor would be:
|
|
|
+ and the implementation of the destructor would be:
|
|
|
|
|
|
<informalexample>
|
|
|
<programlisting>
|
|
|
@@ -4943,7 +4938,7 @@ struct _snd_pcm_runtime {
|
|
|
<para>
|
|
|
The arbitrary file operations can be defined for this
|
|
|
instance. The file operators are defined in
|
|
|
- <parameter>ops</parameter> table. For example, assume that
|
|
|
+ the <parameter>ops</parameter> table. For example, assume that
|
|
|
this chip needs an ioctl.
|
|
|
|
|
|
<informalexample>
|
|
|
@@ -4964,7 +4959,7 @@ struct _snd_pcm_runtime {
|
|
|
<title>IEC958 (S/PDIF)</title>
|
|
|
<para>
|
|
|
Usually the controls for IEC958 devices are implemented via
|
|
|
- control interface. There is a macro to compose a name string for
|
|
|
+ the control interface. There is a macro to compose a name string for
|
|
|
IEC958 controls, <function>SNDRV_CTL_NAME_IEC958()</function>
|
|
|
defined in <filename><include/asound.h></filename>.
|
|
|
</para>
|
|
|
@@ -4973,7 +4968,7 @@ struct _snd_pcm_runtime {
|
|
|
There are some standard controls for IEC958 status bits. These
|
|
|
controls use the type <type>SNDRV_CTL_ELEM_TYPE_IEC958</type>,
|
|
|
and the size of element is fixed as 4 bytes array
|
|
|
- (value.iec958.status[x]). For <structfield>info</structfield>
|
|
|
+ (value.iec958.status[x]). For the <structfield>info</structfield>
|
|
|
callback, you don't specify
|
|
|
the value field for this type (the count field must be set,
|
|
|
though).
|
|
|
@@ -5001,7 +4996,7 @@ struct _snd_pcm_runtime {
|
|
|
enable/disable or to set the raw bit mode. The implementation
|
|
|
will depend on the chip, but the control should be named as
|
|
|
<quote>IEC958 xxx</quote>, preferably using
|
|
|
- <function>SNDRV_CTL_NAME_IEC958()</function> macro.
|
|
|
+ the <function>SNDRV_CTL_NAME_IEC958()</function> macro.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
@@ -5036,12 +5031,12 @@ struct _snd_pcm_runtime {
|
|
|
The allocation of pages with fallback is
|
|
|
<function>snd_malloc_xxx_pages_fallback()</function>. This
|
|
|
function tries to allocate the specified pages but if the pages
|
|
|
- are not available, it tries to reduce the page sizes until the
|
|
|
+ are not available, it tries to reduce the page sizes until
|
|
|
enough space is found.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- For releasing the space, call
|
|
|
+ The release the pages, call
|
|
|
<function>snd_free_xxx_pages()</function> function.
|
|
|
</para>
|
|
|
|
|
|
@@ -5050,8 +5045,8 @@ struct _snd_pcm_runtime {
|
|
|
a large contiguous physical space
|
|
|
at the time the module is loaded for the later use.
|
|
|
This is called <quote>pre-allocation</quote>.
|
|
|
- As already written, you can call the following function at the
|
|
|
- construction of pcm instance (in the case of PCI bus).
|
|
|
+ As already written, you can call the following function at
|
|
|
+ pcm instance construction time (in the case of PCI bus).
|
|
|
|
|
|
<informalexample>
|
|
|
<programlisting>
|
|
|
@@ -5063,34 +5058,34 @@ struct _snd_pcm_runtime {
|
|
|
</informalexample>
|
|
|
|
|
|
where <parameter>size</parameter> is the byte size to be
|
|
|
- pre-allocated and the <parameter>max</parameter> is the maximal
|
|
|
- size to be changed via <filename>prealloc</filename> proc file.
|
|
|
- The allocator will try to get as large area as possible
|
|
|
+ pre-allocated and the <parameter>max</parameter> is the maximum
|
|
|
+ size to be changed via the <filename>prealloc</filename> proc file.
|
|
|
+ The allocator will try to get an area as large as possible
|
|
|
within the given size.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
The second argument (type) and the third argument (device pointer)
|
|
|
are dependent on the bus.
|
|
|
- In the case of ISA bus, pass <function>snd_dma_isa_data()</function>
|
|
|
+ In the case of the ISA bus, pass <function>snd_dma_isa_data()</function>
|
|
|
as the third argument with <constant>SNDRV_DMA_TYPE_DEV</constant> type.
|
|
|
For the continuous buffer unrelated to the bus can be pre-allocated
|
|
|
with <constant>SNDRV_DMA_TYPE_CONTINUOUS</constant> type and the
|
|
|
<function>snd_dma_continuous_data(GFP_KERNEL)</function> device pointer,
|
|
|
- whereh <constant>GFP_KERNEL</constant> is the kernel allocation flag to
|
|
|
+ where <constant>GFP_KERNEL</constant> is the kernel allocation flag to
|
|
|
use. For the SBUS, <constant>SNDRV_DMA_TYPE_SBUS</constant> and
|
|
|
<function>snd_dma_sbus_data(sbus_dev)</function> are used instead.
|
|
|
For the PCI scatter-gather buffers, use
|
|
|
<constant>SNDRV_DMA_TYPE_DEV_SG</constant> with
|
|
|
<function>snd_dma_pci_data(pci)</function>
|
|
|
- (see the section
|
|
|
+ (see the
|
|
|
<link linkend="buffer-and-memory-non-contiguous"><citetitle>Non-Contiguous Buffers
|
|
|
- </citetitle></link>).
|
|
|
+ </citetitle></link> section).
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- Once when the buffer is pre-allocated, you can use the
|
|
|
- allocator in the <structfield>hw_params</structfield> callback
|
|
|
+ Once the buffer is pre-allocated, you can use the
|
|
|
+ allocator in the <structfield>hw_params</structfield> callback:
|
|
|
|
|
|
<informalexample>
|
|
|
<programlisting>
|
|
|
@@ -5116,8 +5111,8 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- The first case works fine if the external hardware buffer is enough
|
|
|
- large. This method doesn't need any extra buffers and thus is
|
|
|
+ The first case works fine if the external hardware buffer is large
|
|
|
+ enough. This method doesn't need any extra buffers and thus is
|
|
|
more effective. You need to define the
|
|
|
<structfield>copy</structfield> and
|
|
|
<structfield>silence</structfield> callbacks for
|
|
|
@@ -5127,25 +5122,25 @@ struct _snd_pcm_runtime {
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- The second case allows the mmap of the buffer, although you have
|
|
|
- to handle an interrupt or a tasklet for transferring the data
|
|
|
+ The second case allows for mmap on the buffer, although you have
|
|
|
+ to handle an interrupt or a tasklet to transfer the data
|
|
|
from the intermediate buffer to the hardware buffer. You can find an
|
|
|
- example in vxpocket driver.
|
|
|
+ example in the vxpocket driver.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- Another case is that the chip uses a PCI memory-map
|
|
|
+ Another case is when the chip uses a PCI memory-map
|
|
|
region for the buffer instead of the host memory. In this case,
|
|
|
- mmap is available only on certain architectures like intel. In
|
|
|
- non-mmap mode, the data cannot be transferred as the normal
|
|
|
- way. Thus you need to define <structfield>copy</structfield> and
|
|
|
- <structfield>silence</structfield> callbacks as well
|
|
|
+ mmap is available only on certain architectures like the Intel one.
|
|
|
+ In non-mmap mode, the data cannot be transferred as in the normal
|
|
|
+ way. Thus you need to define the <structfield>copy</structfield> and
|
|
|
+ <structfield>silence</structfield> callbacks as well,
|
|
|
as in the cases above. The examples are found in
|
|
|
<filename>rme32.c</filename> and <filename>rme96.c</filename>.
|
|
|
</para>
|
|
|
|
|
|
<para>
|
|
|
- The implementation of <structfield>copy</structfield> and
|
|
|
+ The implementation of the <structfield>copy</structfield> and
|
|
|
<structfield>silence</structfield> callbacks depends upon
|
|
|
whether the hardware supports interleaved or non-interleaved
|
|
|
samples. The <structfield>copy</structfield> callback is
|
|
|
@@ -5184,8 +5179,8 @@ struct _snd_pcm_runtime {
|
|
|
|
|
|
<para>
|
|
|
What you have to do in this callback is again different
|
|
|
- between playback and capture directions. In the case of
|
|
|
- playback, you do: copy the given amount of data
|
|
|
+ between playback and capture directions. In the
|
|
|
+ playback case, you copy the given amount of data
|
|
|
(<parameter>count</parameter>) at the specified pointer
|
|
|
(<parameter>src</parameter>) to the specified offset
|
|
|
(<parameter>pos</parameter>) on the hardware buffer. When
|
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@@ -5202,7 +5197,7 @@ struct _snd_pcm_runtime {
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</para>
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<para>
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- For the capture direction, you do: copy the given amount of
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+ For the capture direction, you copy the given amount of
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data (<parameter>count</parameter>) at the specified offset
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(<parameter>pos</parameter>) on the hardware buffer to the
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specified pointer (<parameter>dst</parameter>).
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@@ -5216,7 +5211,7 @@ struct _snd_pcm_runtime {
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</programlisting>
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</informalexample>
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- Note that both of the position and the data amount are given
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+ Note that both the position and the amount of data are given
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in frames.
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</para>
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@@ -5247,7 +5242,7 @@ struct _snd_pcm_runtime {
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</para>
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<para>
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- The meanings of arguments are identical with the
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+ The meanings of arguments are the same as in the
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<structfield>copy</structfield>
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callback, although there is no <parameter>src/dst</parameter>
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argument. In the case of interleaved samples, the channel
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@@ -5284,8 +5279,8 @@ struct _snd_pcm_runtime {
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<section id="buffer-and-memory-non-contiguous">
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<title>Non-Contiguous Buffers</title>
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<para>
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- If your hardware supports the page table like emu10k1 or the
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- buffer descriptors like via82xx, you can use the scatter-gather
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+ If your hardware supports the page table as in emu10k1 or the
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+ buffer descriptors as in via82xx, you can use the scatter-gather
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(SG) DMA. ALSA provides an interface for handling SG-buffers.
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The API is provided in <filename><sound/pcm.h></filename>.
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</para>
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@@ -5296,7 +5291,7 @@ struct _snd_pcm_runtime {
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<function>snd_pcm_lib_preallocate_pages_for_all()</function>
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with <constant>SNDRV_DMA_TYPE_DEV_SG</constant>
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in the PCM constructor like other PCI pre-allocator.
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- You need to pass the <function>snd_dma_pci_data(pci)</function>,
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+ You need to pass <function>snd_dma_pci_data(pci)</function>,
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where pci is the struct <structname>pci_dev</structname> pointer
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of the chip as well.
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The <type>struct snd_sg_buf</type> instance is created as
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@@ -5314,7 +5309,7 @@ struct _snd_pcm_runtime {
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<para>
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Then call <function>snd_pcm_lib_malloc_pages()</function>
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- in <structfield>hw_params</structfield> callback
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+ in the <structfield>hw_params</structfield> callback
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as well as in the case of normal PCI buffer.
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The SG-buffer handler will allocate the non-contiguous kernel
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pages of the given size and map them onto the virtually contiguous
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@@ -5335,7 +5330,7 @@ struct _snd_pcm_runtime {
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</para>
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<para>
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- For releasing the data, call
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+ To release the data, call
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<function>snd_pcm_lib_free_pages()</function> in the
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<structfield>hw_free</structfield> callback as usual.
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</para>
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@@ -5390,7 +5385,7 @@ struct _snd_pcm_runtime {
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</para>
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<para>
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- For creating a proc file, call
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+ To create a proc file, call
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<function>snd_card_proc_new()</function>.
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<informalexample>
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@@ -5402,7 +5397,7 @@ struct _snd_pcm_runtime {
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</programlisting>
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</informalexample>
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- where the second argument specifies the proc-file name to be
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+ where the second argument specifies the name of the proc file to be
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created. The above example will create a file
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<filename>my-file</filename> under the card directory,
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e.g. <filename>/proc/asound/card0/my-file</filename>.
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@@ -5417,8 +5412,8 @@ struct _snd_pcm_runtime {
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<para>
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When the creation is successful, the function stores a new
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- instance at the pointer given in the third argument.
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- It is initialized as a text proc file for read only. For using
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+ instance in the pointer given in the third argument.
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+ It is initialized as a text proc file for read only. To use
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this proc file as a read-only text file as it is, set the read
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callback with a private data via
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<function>snd_info_set_text_ops()</function>.
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@@ -5470,9 +5465,9 @@ struct _snd_pcm_runtime {
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</para>
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<para>
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- The file permission can be changed afterwards. As default, it's
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- set as read only for all users. If you want to add the write
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- permission to the user (root as default), set like below:
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+ The file permissions can be changed afterwards. As default, it's
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+ set as read only for all users. If you want to add write
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+ permission for the user (root as default), do as follows:
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<informalexample>
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<programlisting>
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@@ -5503,7 +5498,7 @@ struct _snd_pcm_runtime {
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</para>
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<para>
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- For a raw-data proc-file, set the attributes like the following:
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+ For a raw-data proc-file, set the attributes as follows:
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<informalexample>
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<programlisting>
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@@ -5524,7 +5519,7 @@ struct _snd_pcm_runtime {
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<para>
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The callback is much more complicated than the text-file
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- version. You need to use a low-level i/o functions such as
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+ version. You need to use a low-level I/O functions such as
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<function>copy_from/to_user()</function> to transfer the
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data.
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@@ -5560,28 +5555,28 @@ struct _snd_pcm_runtime {
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<title>Power Management</title>
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<para>
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If the chip is supposed to work with suspend/resume
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- functions, you need to add the power-management codes to the
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- driver. The additional codes for the power-management should be
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+ functions, you need to add power-management code to the
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+ driver. The additional code for power-management should be
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<function>ifdef</function>'ed with
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<constant>CONFIG_PM</constant>.
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</para>
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<para>
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- If the driver supports the suspend/resume
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- <emphasis>fully</emphasis>, that is, the device can be
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- properly resumed to the status at the suspend is called,
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- you can set <constant>SNDRV_PCM_INFO_RESUME</constant> flag
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- to pcm info field. Usually, this is possible when the
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- registers of ths chip can be safely saved and restored to the
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- RAM. If this is set, the trigger callback is called with
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- <constant>SNDRV_PCM_TRIGGER_RESUME</constant> after resume
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- callback is finished.
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+ If the driver <emphasis>fully</emphasis> supports suspend/resume
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+ that is, the device can be
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+ properly resumed to its state when suspend was called,
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+ you can set the <constant>SNDRV_PCM_INFO_RESUME</constant> flag
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+ in the pcm info field. Usually, this is possible when the
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+ registers of the chip can be safely saved and restored to
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+ RAM. If this is set, the trigger callback is called with
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+ <constant>SNDRV_PCM_TRIGGER_RESUME</constant> after the resume
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+ callback completes.
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</para>
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<para>
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- Even if the driver doesn't support PM fully but only the
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- partial suspend/resume is possible, it's still worthy to
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- implement suspend/resume callbacks. In such a case, applications
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+ Even if the driver doesn't support PM fully but
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+ partial suspend/resume is still possible, it's still worthy to
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+ implement suspend/resume callbacks. In such a case, applications
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would reset the status by calling
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<function>snd_pcm_prepare()</function> and restart the stream
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appropriately. Hence, you can define suspend/resume callbacks
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@@ -5590,22 +5585,22 @@ struct _snd_pcm_runtime {
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</para>
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<para>
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- Note that the trigger with SUSPEND can be always called when
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+ Note that the trigger with SUSPEND can always be called when
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<function>snd_pcm_suspend_all</function> is called,
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- regardless of <constant>SNDRV_PCM_INFO_RESUME</constant> flag.
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+ regardless of the <constant>SNDRV_PCM_INFO_RESUME</constant> flag.
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The <constant>RESUME</constant> flag affects only the behavior
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of <function>snd_pcm_resume()</function>.
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(Thus, in theory,
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<constant>SNDRV_PCM_TRIGGER_RESUME</constant> isn't needed
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to be handled in the trigger callback when no
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<constant>SNDRV_PCM_INFO_RESUME</constant> flag is set. But,
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- it's better to keep it for compatibility reason.)
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+ it's better to keep it for compatibility reasons.)
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</para>
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<para>
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In the earlier version of ALSA drivers, a common
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power-management layer was provided, but it has been removed.
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The driver needs to define the suspend/resume hooks according to
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- the bus the device is assigned. In the case of PCI driver, the
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+ the bus the device is connected to. In the case of PCI drivers, the
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callbacks look like below:
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<informalexample>
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@@ -5629,7 +5624,7 @@ struct _snd_pcm_runtime {
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</para>
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<para>
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- The scheme of the real suspend job is as following.
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+ The scheme of the real suspend job is as follows.
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<orderedlist>
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<listitem><para>Retrieve the card and the chip data.</para></listitem>
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@@ -5679,11 +5674,11 @@ struct _snd_pcm_runtime {
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</para>
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<para>
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- The scheme of the real resume job is as following.
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+ The scheme of the real resume job is as follows.
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<orderedlist>
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<listitem><para>Retrieve the card and the chip data.</para></listitem>
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- <listitem><para>Set up PCI. First, call <function>pci_restore_state()</function>.
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+ <listitem><para>Set up PCI. First, call <function>pci_restore_state()</function>.
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Then enable the pci device again by calling <function>pci_enable_device()</function>.
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Call <function>pci_set_master()</function> if necessary, too.</para></listitem>
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<listitem><para>Re-initialize the chip.</para></listitem>
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@@ -5734,7 +5729,7 @@ struct _snd_pcm_runtime {
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<function>snd_pcm_suspend_all()</function> or
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<function>snd_pcm_suspend()</function>. It means that the PCM
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streams are already stoppped when the register snapshot is
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- taken. But, remind that you don't have to restart the PCM
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+ taken. But, remember that you don't have to restart the PCM
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stream in the resume callback. It'll be restarted via
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trigger call with <constant>SNDRV_PCM_TRIGGER_RESUME</constant>
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when necessary.
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@@ -5795,7 +5790,7 @@ struct _snd_pcm_runtime {
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</para>
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<para>
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- If you need a space for saving the registers, allocate the
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+ If you need a space to save the registers, allocate the
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buffer for it here, too, since it would be fatal
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if you cannot allocate a memory in the suspend phase.
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The allocated buffer should be released in the corresponding
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@@ -5833,7 +5828,7 @@ struct _snd_pcm_runtime {
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<title>Module Parameters</title>
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<para>
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There are standard module options for ALSA. At least, each
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- module should have <parameter>index</parameter>,
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+ module should have the <parameter>index</parameter>,
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<parameter>id</parameter> and <parameter>enable</parameter>
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options.
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</para>
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@@ -5841,8 +5836,8 @@ struct _snd_pcm_runtime {
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<para>
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If the module supports multiple cards (usually up to
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8 = <constant>SNDRV_CARDS</constant> cards), they should be
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- arrays. The default initial values are defined already as
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- constants for ease of programming:
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+ arrays. The default initial values are defined already as
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+ constants for easier programming:
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<informalexample>
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<programlisting>
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@@ -5858,7 +5853,7 @@ struct _snd_pcm_runtime {
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<para>
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If the module supports only a single card, they could be single
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variables, instead. <parameter>enable</parameter> option is not
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- always necessary in this case, but it wouldn't be so bad to have a
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+ always necessary in this case, but it would be better to have a
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dummy option for compatibility.
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</para>
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@@ -5923,22 +5918,22 @@ struct _snd_pcm_runtime {
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</para>
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<para>
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- Suppose that you'll create a new PCI driver for the card
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+ Suppose that you create a new PCI driver for the card
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<quote>xyz</quote>. The card module name would be
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- snd-xyz. The new driver is usually put into alsa-driver
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+ snd-xyz. The new driver is usually put into the alsa-driver
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tree, <filename>alsa-driver/pci</filename> directory in
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the case of PCI cards.
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Then the driver is evaluated, audited and tested
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by developers and users. After a certain time, the driver
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- will go to alsa-kernel tree (to the corresponding directory,
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+ will go to the alsa-kernel tree (to the corresponding directory,
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such as <filename>alsa-kernel/pci</filename>) and eventually
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- integrated into Linux 2.6 tree (the directory would be
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+ will be integrated into the Linux 2.6 tree (the directory would be
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<filename>linux/sound/pci</filename>).
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</para>
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<para>
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In the following sections, the driver code is supposed
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- to be put into alsa-driver tree. The two cases are assumed:
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+ to be put into alsa-driver tree. The two cases are covered:
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a driver consisting of a single source file and one consisting
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of several source files.
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</para>
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@@ -6033,7 +6028,7 @@ struct _snd_pcm_runtime {
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<listitem>
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<para>
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Add a new directory (<filename>xyz</filename>) in
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- <filename>alsa-driver/pci/Makefile</filename> like below
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+ <filename>alsa-driver/pci/Makefile</filename> as below
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<informalexample>
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<programlisting>
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@@ -6102,7 +6097,7 @@ struct _snd_pcm_runtime {
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<section id="useful-functions-snd-printk">
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<title><function>snd_printk()</function> and friends</title>
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<para>
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- ALSA provides a verbose version of
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+ ALSA provides a verbose version of the
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<function>printk()</function> function. If a kernel config
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<constant>CONFIG_SND_VERBOSE_PRINTK</constant> is set, this
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function prints the given message together with the file name
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@@ -6170,7 +6165,7 @@ struct _snd_pcm_runtime {
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<section id="useful-functions-snd-bug">
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<title><function>snd_BUG()</function></title>
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<para>
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- It shows <computeroutput>BUG?</computeroutput> message and
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+ It shows the <computeroutput>BUG?</computeroutput> message and
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stack trace as well as <function>snd_assert</function> at the point.
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It's useful to show that a fatal error happens there.
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</para>
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@@ -6199,6 +6194,4 @@ struct _snd_pcm_runtime {
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in the hardware constraints section.
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</para>
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</chapter>
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-
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-
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</book>
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Linus Torvalds