drm: add helper for printing to log or seq_file

Sometimes it is nice not to duplicate equivalent printk() and
seq_printf() code.

v2: simplify things w/ va_format, and use dev_printk, docs

Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1478358492-30738-3-git-send-email-robdclark@gmail.com

Documentation/gpu/drm-internals.rst

@@ -350,6 +350,23 @@ how the ioctl is allowed to be called.
 .. kernel-doc:: drivers/gpu/drm/drm_ioctl.c
    :export:
 
+
+Misc Utilities
+==============
+
+Printer
+-------
+
+.. kernel-doc:: include/drm/drm_print.h
+   :doc: print
+
+.. kernel-doc:: include/drm/drm_print.h
+   :internal:
+
+.. kernel-doc:: include/drm/drm_print.h
+   :export:
+
+
 Legacy Support Code
 ===================
 

drivers/gpu/drm/Makefile

@@ -15,7 +15,7 @@ drm-y       :=	drm_auth.o drm_bufs.o drm_cache.o \
 		drm_modeset_lock.o drm_atomic.o drm_bridge.o \
 		drm_framebuffer.o drm_connector.o drm_blend.o \
 		drm_encoder.o drm_mode_object.o drm_property.o \
-		drm_plane.o drm_color_mgmt.o
+		drm_plane.o drm_color_mgmt.o drm_print.o
 
 drm-$(CONFIG_COMPAT) += drm_ioc32.o
 drm-$(CONFIG_DRM_GEM_CMA_HELPER) += drm_gem_cma_helper.o

drivers/gpu/drm/drm_print.c

@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2016 Red Hat
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Authors:
+ * Rob Clark <robdclark@gmail.com>
+ */
+
+#include <stdarg.h>
+#include <linux/seq_file.h>
+#include <drm/drmP.h>
+#include <drm/drm_print.h>
+
+void __drm_printfn_seq_file(struct drm_printer *p, struct va_format *vaf)
+{
+	seq_printf(p->arg, "%pV", vaf);
+}
+EXPORT_SYMBOL(__drm_printfn_seq_file);
+
+void __drm_printfn_info(struct drm_printer *p, struct va_format *vaf)
+{
+	dev_printk(KERN_INFO, p->arg, "[" DRM_NAME "] %pV", vaf);
+}
+EXPORT_SYMBOL(__drm_printfn_info);
+
+void drm_printf(struct drm_printer *p, const char *f, ...)
+{
+	struct va_format vaf;
+	va_list args;
+
+	va_start(args, f);
+	vaf.fmt = f;
+	vaf.va = &args;
+	p->printfn(p, &vaf);
+	va_end(args);
+}
+EXPORT_SYMBOL(drm_printf);

include/drm/drm_print.h

@@ -0,0 +1,117 @@
+/*
+ * Copyright (C) 2016 Red Hat
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Authors:
+ * Rob Clark <robdclark@gmail.com>
+ */
+
+#ifndef DRM_PRINT_H_
+#define DRM_PRINT_H_
+
+#include <linux/seq_file.h>
+#include <linux/device.h>
+
+/**
+ * DOC: print
+ *
+ * A simple wrapper for dev_printk(), seq_printf(), etc.  Allows same
+ * debug code to be used for both debugfs and printk logging.
+ *
+ * For example::
+ *
+ *     void log_some_info(struct drm_printer *p)
+ *     {
+ *             drm_printf(p, "foo=%d\n", foo);
+ *             drm_printf(p, "bar=%d\n", bar);
+ *     }
+ *
+ *     #ifdef CONFIG_DEBUG_FS
+ *     void debugfs_show(struct seq_file *f)
+ *     {
+ *             struct drm_printer p = drm_seq_file_printer(f);
+ *             log_some_info(&p);
+ *     }
+ *     #endif
+ *
+ *     void some_other_function(...)
+ *     {
+ *             struct drm_printer p = drm_info_printer(drm->dev);
+ *             log_some_info(&p);
+ *     }
+ */
+
+/**
+ * struct drm_printer - drm output "stream"
+ * @printfn: actual output fxn
+ * @arg: output fxn specific data
+ *
+ * Do not use struct members directly.  Use drm_printer_seq_file(),
+ * drm_printer_info(), etc to initialize.  And drm_printf() for output.
+ */
+struct drm_printer {
+	void (*printfn)(struct drm_printer *p, struct va_format *vaf);
+	void *arg;
+};
+
+void __drm_printfn_seq_file(struct drm_printer *p, struct va_format *vaf);
+void __drm_printfn_info(struct drm_printer *p, struct va_format *vaf);
+
+/**
+ * drm_printf - print to a &drm_printer stream
+ * @p: the &drm_printer
+ * @f: format string
+ */
+void drm_printf(struct drm_printer *p, const char *f, ...);
+
+
+/**
+ * drm_seq_file_printer - construct a &drm_printer that outputs to &seq_file
+ * @f:  the struct &seq_file to output to
+ *
+ * RETURNS:
+ * The &drm_printer object
+ */
+static inline struct drm_printer drm_seq_file_printer(struct seq_file *f)
+{
+	struct drm_printer p = {
+		.printfn = __drm_printfn_seq_file,
+		.arg = f,
+	};
+	return p;
+}
+
+/**
+ * drm_info_printer - construct a &drm_printer that outputs to dev_printk()
+ * @dev: the struct &device pointer
+ *
+ * RETURNS:
+ * The &drm_printer object
+ */
+static inline struct drm_printer drm_info_printer(struct device *dev)
+{
+	struct drm_printer p = {
+		.printfn = __drm_printfn_info,
+		.arg = dev,
+	};
+	return p;
+}
+
+#endif /* DRM_PRINT_H_ */