libv4l: ensure libv4l gets built, fixes mediastreamer build

In commit f837251785e9389f53d695ddb8a094707865171b ("package/libv4l:
allow build of v4l2 utilities on noMMU platforms"), Hugues Fruchet
added a bunch of patches to libv4l in order to allow the v4l utilities
to be built on noMMU platforms.

However, as part of those patches, he entirely disabled the build of
libv4l in static linking configurations, because libv4l uses
dlopen(). Unfortunately, this breaks the build of applications like
mediastreamer in static linking configurations, and generally makes
our libv4l packages a little bit awkward: you can enable it, but it
doesn't install anything (in static linking configurations).

A closer look shows that dlopen() is only used by libv4l for plugin
support, and libv4l only provides one single plugin, and its build is
already conditional. Therefore, this commit adds yet another patch to
libv4l, which re-enables the build of libv4l, but disables the
plugin-related logic when plugin support is disabled (and it was
already automatically disabled in static linking configurations).

While at it, we update the comment in libv4l.mk that lists the patches
that makes autoreconf necessary.

Fixes the build of mediastreamer:

  http://autobuild.buildroot.net/results/af091cfd0508df9395778cdc796f77e95c168410/

Cc: Hugues Fruchet <hugues.fruchet@st.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/libv4l/0011-configure.ac-drop-disable-libv4l-disable-plugin-supp.patch

@@ -0,0 +1,217 @@
+From 305ae25455b1f19ad2eda92523bd553fd8bc72fd Mon Sep 17 00:00:00 2001
+From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+Date: Sun, 20 Aug 2017 23:58:44 +0200
+Subject: [PATCH] configure.ac: drop --disable-libv4l, disable plugin support
+ instead
+
+In commit 2e604dfbcd09b93f0808cedb2a0b324c5569a599 ("configure.ac: add
+--disable-libv4l option"), an option --disable-libv4l was added. As
+part of this, libv4l is no longer built at all in static linking
+configurations, just because libv4l uses dlopen() for plugin support.
+
+However, plugin support is only a side feature of libv4l, and one may
+need to use libv4l in static configurations, just without plugin
+support.
+
+Therefore, this commit:
+
+ - Essentially reverts 2e604dfbcd09b93f0808cedb2a0b324c5569a599, so
+   that libv4l can be built in static linking configurations again.
+
+ - Adjusts the compilation of libv4l2 so that the plugin support is
+   not compiled in when dlopen() in static linking configuration
+   (dlopen is not available).
+
+Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+Submitted-upstream: https://www.mail-archive.com/linux-media@vger.kernel.org/msg117449.html
+---
+ Makefile.am                       | 11 ++---------
+ configure.ac                      | 15 +++------------
+ lib/libv4l2/Makefile.am           |  6 +++++-
+ lib/libv4l2/libv4l2-priv.h        | 14 ++++++++++++++
+ utils/Makefile.am                 |  6 +-----
+ utils/v4l2-compliance/Makefile.am |  4 ----
+ utils/v4l2-ctl/Makefile.am        |  4 ----
+ 7 files changed, 25 insertions(+), 35 deletions(-)
+
+diff --git a/Makefile.am b/Makefile.am
+index 07c3ef8..e603472 100644
+--- a/Makefile.am
++++ b/Makefile.am
+@@ -1,17 +1,10 @@
+ AUTOMAKE_OPTIONS = foreign
+ ACLOCAL_AMFLAGS = -I m4
+ 
+-SUBDIRS = v4l-utils-po libdvbv5-po
+-
+-if WITH_LIBV4L
+-SUBDIRS += lib
+-endif
++SUBDIRS = v4l-utils-po libdvbv5-po lib
+ 
+ if WITH_V4LUTILS
+-SUBDIRS += utils
+-if WITH_LIBV4L
+-SUBDIRS += contrib
+-endif
++SUBDIRS += utils contrib
+ endif
+ 
+ EXTRA_DIST = android-config.h bootstrap.sh doxygen_libdvbv5.cfg include COPYING.libv4l \
+diff --git a/configure.ac b/configure.ac
+index 58fb688..2ecb4a1 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -374,14 +374,6 @@ AC_ARG_ENABLE(libdvbv5,
+    esac]
+ )
+ 
+-AC_ARG_ENABLE(libv4l,
+-  AS_HELP_STRING([--disable-libv4l], [disable libv4l compilation]),
+-  [case "${enableval}" in
+-     yes | no ) ;;
+-     *) AC_MSG_ERROR(bad value ${enableval} for --disable-libv4l) ;;
+-   esac]
+-)
+-
+ AC_ARG_ENABLE(dyn-libv4l,
+   AS_HELP_STRING([--disable-dyn-libv4l], [disable dynamic libv4l support]),
+   [case "${enableval}" in
+@@ -439,7 +431,6 @@ AM_CONDITIONAL([WITH_LIBDVBV5],     [test x$enable_libdvbv5  != xno -a x$have_li
+ AM_CONDITIONAL([WITH_DVBV5_REMOTE], [test x$enable_libdvbv5  != xno -a x$have_libudev = xyes -a x$have_pthread = xyes])
+ 
+ AM_CONDITIONAL([WITH_DYN_LIBV4L],   [test x$enable_dyn_libv4l != xno])
+-AM_CONDITIONAL([WITH_LIBV4L],       [test x$enable_libv4l    != xno -a x$enable_shared != xno])
+ AM_CONDITIONAL([WITH_V4LUTILS],	    [test x$enable_v4l_utils != xno -a x$linux_os = xyes])
+ AM_CONDITIONAL([WITH_QV4L2],	    [test x${qt_pkgconfig} = xtrue -a x$enable_qv4l2 != xno])
+ AM_CONDITIONAL([WITH_V4L_PLUGINS],  [test x$enable_dyn_libv4l != xno -a x$enable_shared != xno])
+@@ -467,11 +458,12 @@ AM_COND_IF([WITH_LIBDVBV5], [USE_LIBDVBV5="yes"], [USE_LIBDVBV5="no"])
+ AM_COND_IF([WITH_DVBV5_REMOTE], [USE_DVBV5_REMOTE="yes"
+ 				 AC_DEFINE([HAVE_DVBV5_REMOTE], [1], [Usage of DVBv5 remote enabled])],
+ 			        [USE_DVBV5_REMOTE="no"])
+-AM_COND_IF([WITH_LIBV4L], [USE_LIBV4L="yes"], [USE_LIBV4L="no"])
+ AM_COND_IF([WITH_DYN_LIBV4L], [USE_DYN_LIBV4L="yes"], [USE_DYN_LIBV4L="no"])
+ AM_COND_IF([WITH_V4LUTILS], [USE_V4LUTILS="yes"], [USE_V4LUTILS="no"])
+ AM_COND_IF([WITH_QV4L2], [USE_QV4L2="yes"], [USE_QV4L2="no"])
+-AM_COND_IF([WITH_V4L_PLUGINS], [USE_V4L_PLUGINS="yes"], [USE_V4L_PLUGINS="no"])
++AM_COND_IF([WITH_V4L_PLUGINS], [USE_V4L_PLUGINS="yes"
++				AC_DEFINE([HAVE_V4L_PLUGINS], [1], [V4L plugin support enabled])],
++				[USE_V4L_PLUGINS="no"])
+ AM_COND_IF([WITH_V4L_WRAPPERS], [USE_V4L_WRAPPERS="yes"], [USE_V4L_WRAPPERS="no"])
+ AM_COND_IF([WITH_GCONV], [USE_GCONV="yes"], [USE_GCONV="no"])
+ AM_COND_IF([WITH_V4L2_CTL_LIBV4L], [USE_V4L2_CTL_LIBV4L="yes"], [USE_V4L2_CTL_LIBV4L="no"])
+@@ -503,7 +495,6 @@ compile time options summary
+ 
+     gconv                      : $USE_GCONV
+ 
+-    libv4l                     : $USE_LIBV4L
+     dynamic libv4l             : $USE_DYN_LIBV4L
+     v4l_plugins                : $USE_V4L_PLUGINS
+     v4l_wrappers               : $USE_V4L_WRAPPERS
+diff --git a/lib/libv4l2/Makefile.am b/lib/libv4l2/Makefile.am
+index 811c45c..3a1bb90 100644
+--- a/lib/libv4l2/Makefile.am
++++ b/lib/libv4l2/Makefile.am
+@@ -15,7 +15,11 @@ else
+ noinst_LTLIBRARIES = libv4l2.la
+ endif
+ 
+-libv4l2_la_SOURCES = libv4l2.c v4l2-plugin.c log.c libv4l2-priv.h
++libv4l2_la_SOURCES = libv4l2.c log.c libv4l2-priv.h
++if WITH_V4L_PLUGINS
++libv4l2_la_SOURCES += v4l2-plugin.c
++endif
++
+ libv4l2_la_CPPFLAGS = $(CFLAG_VISIBILITY) $(ENFORCE_LIBV4L_STATIC)
+ libv4l2_la_LDFLAGS = $(LIBV4L2_VERSION) -lpthread $(DLOPEN_LIBS) $(ENFORCE_LIBV4L_STATIC)
+ libv4l2_la_LIBADD = ../libv4lconvert/libv4lconvert.la
+diff --git a/lib/libv4l2/libv4l2-priv.h b/lib/libv4l2/libv4l2-priv.h
+index 343db5e..1924c91 100644
+--- a/lib/libv4l2/libv4l2-priv.h
++++ b/lib/libv4l2/libv4l2-priv.h
+@@ -107,10 +107,24 @@ struct v4l2_dev_info {
+ };
+ 
+ /* From v4l2-plugin.c */
++#if defined(HAVE_V4L_PLUGINS)
+ void v4l2_plugin_init(int fd, void **plugin_lib_ret, void **plugin_priv_ret,
+ 		      const struct libv4l_dev_ops **dev_ops_ret);
+ void v4l2_plugin_cleanup(void *plugin_lib, void *plugin_priv,
+ 			 const struct libv4l_dev_ops *dev_ops);
++#else
++static inline void v4l2_plugin_init(int fd, void **plugin_lib_ret, void **plugin_priv_ret,
++				    const struct libv4l_dev_ops **dev_ops_ret)
++{
++	*dev_ops_ret = v4lconvert_get_default_dev_ops();
++	*plugin_lib_ret = NULL;
++	*plugin_priv_ret = NULL;
++}
++static inline void v4l2_plugin_cleanup(void *plugin_lib, void *plugin_priv,
++				       const struct libv4l_dev_ops *dev_ops)
++{
++}
++#endif /* WITH_V4L_PLUGINS */
+ 
+ /* From log.c */
+ extern const char *v4l2_ioctls[];
+diff --git a/utils/Makefile.am b/utils/Makefile.am
+index ce710c2..d7708cc 100644
+--- a/utils/Makefile.am
++++ b/utils/Makefile.am
+@@ -13,12 +13,8 @@ SUBDIRS = \
+ 	v4l2-sysfs-path \
+ 	cec-ctl \
+ 	cec-compliance \
+-	cec-follower
+-
+-if WITH_LIBV4L
+-SUBDIRS += \
++	cec-follower \
+ 	rds-ctl
+-endif
+ 
+ if WITH_LIBDVBV5
+ SUBDIRS += \
+diff --git a/utils/v4l2-compliance/Makefile.am b/utils/v4l2-compliance/Makefile.am
+index 0240a50..c2b5919 100644
+--- a/utils/v4l2-compliance/Makefile.am
++++ b/utils/v4l2-compliance/Makefile.am
+@@ -7,16 +7,12 @@ v4l2_compliance_SOURCES = v4l2-compliance.cpp v4l2-test-debug.cpp v4l2-test-inpu
+ 	v4l2-test-codecs.cpp v4l2-test-colors.cpp v4l2-compliance.h
+ v4l2_compliance_CPPFLAGS = -I../common
+ 
+-if WITH_LIBV4L
+ if WITH_V4L2_COMPLIANCE_LIBV4L
+ v4l2_compliance_LDADD = ../../lib/libv4l2/libv4l2.la ../../lib/libv4lconvert/libv4lconvert.la -lrt -lpthread
+ else
+ v4l2_compliance_LDADD = -lrt -lpthread
+ DEFS += -DNO_LIBV4L2
+ endif
+-else
+-DEFS += -DNO_LIBV4L2
+-endif
+ 
+ EXTRA_DIST = Android.mk fixme.txt v4l2-compliance.1
+ 
+diff --git a/utils/v4l2-ctl/Makefile.am b/utils/v4l2-ctl/Makefile.am
+index 4475aed..955647d 100644
+--- a/utils/v4l2-ctl/Makefile.am
++++ b/utils/v4l2-ctl/Makefile.am
+@@ -9,14 +9,10 @@ v4l2_ctl_SOURCES = v4l2-ctl.cpp v4l2-ctl.h v4l2-ctl-common.cpp v4l2-ctl-tuner.cp
+ 	v4l2-tpg-colors.c v4l2-tpg-core.c v4l-stream.c
+ v4l2_ctl_CPPFLAGS = -I../common
+ 
+-if WITH_LIBV4L
+ if WITH_V4L2_CTL_LIBV4L
+ v4l2_ctl_LDADD = ../../lib/libv4l2/libv4l2.la ../../lib/libv4lconvert/libv4lconvert.la -lrt -lpthread
+ else
+ DEFS += -DNO_LIBV4L2
+ endif
+-else
+-DEFS += -DNO_LIBV4L2
+-endif
+ 
+ EXTRA_DIST = Android.mk v4l2-ctl.1
+-- 
+2.9.4
+

package/libv4l/libv4l.mk

@@ -18,6 +18,8 @@ LIBV4L_CONF_OPTS = --disable-doxygen-doc
 # 0007-configure.ac-add-disable-libv4l-option.patch
 # 0008-configure.ac-fix-build-of-v4l-utils-on-uclinux.patch
 # 0009-configure.ac-add-USE_LIBV4L-to-summary.patch
+# 0010-Build-libv4lconvert-helper-support-only-when-fork-is.patch
+# 0011-configure.ac-drop-disable-libv4l-disable-plugin-supp.patch
 LIBV4L_AUTORECONF = YES
 # host-gettext needed for autoreconf to work
 LIBV4L_DEPENDENCIES += host-gettext