On Wed, Jan 15, 2020 at 12:28:31PM +0200, Jani Nikula wrote:
> On Tue, 14 Jan 2020, Sean Paul <s...@poorly.run> wrote:
> > From: Sean Paul <seanp...@chromium.org>
> >
> > This patch uses a ring_buffer to keep a "flight recorder" (name credit
> > Weston)
> > of DRM logs for a specified set of debug categories. The user writes a
> > bitmask of debug categories to the "trace_mask" node and can read log
> > messages from the "trace" node.
> >
> > These nodes currently exist in debugfs under the dri directory. I
> > intended on exposing all of this through tracefs originally, but the
> > tracefs entry points are not exposed, so there's no way to create
> > tracefs files from drivers at the moment. I think it would be a
> > worthwhile endeavour, but one requiring more time and conversation to
> > ensure the drm traces fit somewhere sensible.
> >
> > Cc: Daniel Vetter <daniel.vet...@ffwll.ch>
> > Cc: David Airlie <airl...@gmail.com>
> > Cc: Jani Nikula <jani.nik...@linux.intel.com>
> > Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
> > Cc: Pekka Paalanen <ppaala...@gmail.com>
> > Cc: Rob Clark <robdcl...@gmail.com>
> > Cc: Steven Rostedt <rost...@goodmis.org>
> > Cc: Thomas Zimmermann <tzimmerm...@suse.de>
> > Cc: Ville Syrjälä <ville.syrj...@linux.intel.com>
> > Signed-off-by: Sean Paul <seanp...@chromium.org>
> > Link:
> > https://patchwork.freedesktop.org/patch/msgid/20191010204823.195540-1-s...@poorly.run
> > #v1
> > Link:
> > https://lists.freedesktop.org/archives/dri-devel/2019-November/243230.html
> > #v2
> > Link:
> > https://patchwork.freedesktop.org/patch/msgid/20191212203301.142437-1-s...@poorly.run
> > #v3
> >
> > Changes in v2:
> > - Went with a completely different approach:
> > https://lists.freedesktop.org/archives/dri-devel/2019-November/243230.html
> >
> > Changes in v3:
> > - Changed commit message to be a bit less RFC-y
> > - Make class_drm_category_log an actual trace class
> >
> > Changes in v4:
> > - Instead of [ab]using trace events and the system trace buffer, use our
> > own ringbuffer
> > ---
> > ---
> > Documentation/gpu/drm-uapi.rst | 9 +
> > drivers/gpu/drm/Kconfig | 1 +
> > drivers/gpu/drm/Makefile | 2 +-
> > drivers/gpu/drm/drm_drv.c | 3 +
> > drivers/gpu/drm/drm_print.c | 80 +++++--
> > drivers/gpu/drm/drm_trace.c | 376 +++++++++++++++++++++++++++++++++
> > include/drm/drm_print.h | 39 ++++
> > 7 files changed, 487 insertions(+), 23 deletions(-)
> > create mode 100644 drivers/gpu/drm/drm_trace.c
> >
> > diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst
> > index 56fec6ed1ad8..089eb6fd3e94 100644
> > --- a/Documentation/gpu/drm-uapi.rst
> > +++ b/Documentation/gpu/drm-uapi.rst
> > @@ -312,6 +312,15 @@ Debugfs Support
> > .. kernel-doc:: drivers/gpu/drm/drm_debugfs.c
> > :export:
> >
> > +DRM Tracing
> > +---------------
> > +
> > +.. kernel-doc:: drivers/gpu/drm/drm_trace.c
> > + :doc: DRM Tracing
> > +
> > +.. kernel-doc:: drivers/gpu/drm/drm_trace.c
> > + :internal:
> > +
> > Sysfs Support
> > =============
> >
> > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> > index d0aa6cff2e02..9d8077e87afe 100644
> > --- a/drivers/gpu/drm/Kconfig
> > +++ b/drivers/gpu/drm/Kconfig
> > @@ -14,6 +14,7 @@ menuconfig DRM
> > select I2C
> > select I2C_ALGOBIT
> > select DMA_SHARED_BUFFER
> > + select RING_BUFFER
> > select SYNC_FILE
> > help
> > Kernel-level support for the Direct Rendering Infrastructure (DRI)
> > diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> > index 6493088a0fdd..88b4674934e6 100644
> > --- a/drivers/gpu/drm/Makefile
> > +++ b/drivers/gpu/drm/Makefile
> > @@ -29,7 +29,7 @@ drm-$(CONFIG_DRM_PANEL) += drm_panel.o
> > drm-$(CONFIG_OF) += drm_of.o
> > drm-$(CONFIG_AGP) += drm_agpsupport.o
> > drm-$(CONFIG_PCI) += drm_pci.o
> > -drm-$(CONFIG_DEBUG_FS) += drm_debugfs.o drm_debugfs_crc.o
> > +drm-$(CONFIG_DEBUG_FS) += drm_debugfs.o drm_debugfs_crc.o drm_trace.o
> > drm-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
> >
> > drm_vram_helper-y := drm_gem_vram_helper.o \
> > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> > index 7c18a980cd4b..98260b9f8004 100644
> > --- a/drivers/gpu/drm/drm_drv.c
> > +++ b/drivers/gpu/drm/drm_drv.c
> > @@ -1114,6 +1114,7 @@ static const struct file_operations drm_stub_fops = {
> > static void drm_core_exit(void)
> > {
> > unregister_chrdev(DRM_MAJOR, "drm");
> > + drm_trace_cleanup();
> > debugfs_remove(drm_debugfs_root);
> > drm_sysfs_destroy();
> > idr_destroy(&drm_minors_idr);
> > @@ -1135,6 +1136,8 @@ static int __init drm_core_init(void)
> >
> > drm_debugfs_root = debugfs_create_dir("dri", NULL);
> >
> > + WARN_ON(drm_trace_init(drm_debugfs_root));
> > +
> > ret = register_chrdev(DRM_MAJOR, "drm", &drm_stub_fops);
> > if (ret < 0)
> > goto error;
> > diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c
> > index 111b932cf2a9..0ac1867937bf 100644
> > --- a/drivers/gpu/drm/drm_print.c
> > +++ b/drivers/gpu/drm/drm_print.c
> > @@ -262,21 +262,37 @@ void drm_dev_dbg(const struct device *dev, enum
> > drm_debug_category category,
> > struct va_format vaf;
> > va_list args;
> >
> > - if (!drm_debug_enabled(category))
> > - return;
> > -
> > - va_start(args, format);
> > - vaf.fmt = format;
> > - vaf.va = &args;
> > -
> > - if (dev)
> > - dev_printk(KERN_DEBUG, dev, "[" DRM_NAME ":%ps] %pV",
> > - __builtin_return_address(0), &vaf);
> > - else
> > - printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
> > - __builtin_return_address(0), &vaf);
> > + if (drm_debug_enabled(category)) {
> > + va_start(args, format);
> > + vaf.fmt = format;
> > + vaf.va = &args;
> > +
> > + if (dev)
> > + dev_printk(KERN_DEBUG, dev, "[" DRM_NAME ":%ps] %pV",
> > + __builtin_return_address(0), &vaf);
> > + else
> > + printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
> > + __builtin_return_address(0), &vaf);
> > +
> > + va_end(args);
> > + }
> >
> > - va_end(args);
> > + if (drm_trace_enabled(category)) {
> > + va_start(args, format);
> > + vaf.fmt = format;
> > + vaf.va = &args;
> > +
> > + if (dev)
> > + drm_dev_trace_printf(dev, "[%ps] %pV",
> > + __builtin_return_address(0),
> > + &vaf);
> > + else
> > + drm_trace_printf("[%ps] %pV",
> > + __builtin_return_address(0),
> > + &vaf);
> > +
> > + va_end(args);
> > + }
> > }
> > EXPORT_SYMBOL(drm_dev_dbg);
> >
> > @@ -285,17 +301,28 @@ void __drm_dbg(enum drm_debug_category category,
> > const char *format, ...)
> > struct va_format vaf;
> > va_list args;
> >
> > - if (!drm_debug_enabled(category))
> > - return;
> >
> > - va_start(args, format);
> > - vaf.fmt = format;
> > - vaf.va = &args;
> > + if (drm_debug_enabled(category)) {
> > + va_start(args, format);
> > + vaf.fmt = format;
> > + vaf.va = &args;
> >
> > - printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
> > - __builtin_return_address(0), &vaf);
> > + printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV",
> > + __builtin_return_address(0), &vaf);
> >
> > - va_end(args);
> > + va_end(args);
> > + }
> > +
> > + if (drm_trace_enabled(category)) {
> > + va_start(args, format);
> > + vaf.fmt = format;
> > + vaf.va = &args;
> > +
> > + drm_trace_printf("[%ps] %pV", __builtin_return_address(0),
> > + &vaf);
> > +
> > + va_end(args);
> > + }
> > }
> > EXPORT_SYMBOL(__drm_dbg);
> >
> > @@ -312,6 +339,15 @@ void __drm_err(const char *format, ...)
> > __builtin_return_address(0), &vaf);
> >
> > va_end(args);
> > +
> > + va_start(args, format);
> > + vaf.fmt = format;
> > + vaf.va = &args;
> > +
> > + drm_trace_printf("[%ps] *ERROR* %pV", __builtin_return_address(0),
> > + &vaf);
> > +
> > + va_end(args);
>
> All the new non-debug struct drm_device based logging macros I added are
> just thin wrappers around the dev_<level> ones. The only benefit of
> __drm_err() is adding __builtin_return_address(0), which I think should
> not be relevant in an error level print; it should be non-ambiguous
> without it. IMO the function names are noise in non-debug logging. I'd
> consider removing the __drm_err() function altogether:
>
> #define DRM_ERROR(fmt, ...) \
> - __drm_err(fmt, ##__VA_ARGS__)
> + _DRM_PRINTK(, ERR, "*ERROR* " fmt, ##__VA_ARGS__)
Hmm, I think we will want to keep errors in the trace since that makes
debugging from the trace a lot easier (trace timestamps might not line up
exactly with dmesg).
>
> What this means is that you wouldn't get the drm trace on error level
> logging. However, you already weren't getting it on any of the other
> levels either, nor were you getting it for DRM_DEV_ERROR() which uses
> drm_dev_printk().
Ick, this is an oversight on my part, they should be included.
Sean
>
>
> BR,
> Jani.
>
>
> > }
> > EXPORT_SYMBOL(__drm_err);
> >
> > diff --git a/drivers/gpu/drm/drm_trace.c b/drivers/gpu/drm/drm_trace.c
> > new file mode 100644
> > index 000000000000..0e7cf342d1d9
> > --- /dev/null
> > +++ b/drivers/gpu/drm/drm_trace.c
> > @@ -0,0 +1,376 @@
> > +/* SPDX-License-Identifier: MIT */
> > +/*
> > + * Copyright (C) 2020 Google, Inc.
> > + *
> > + * Authors:
> > + * Sean Paul <seanp...@chromium.org>
> > + */
> > +
> > +#include <linux/cpumask.h>
> > +#include <linux/debugfs.h>
> > +#include <linux/kernel.h>
> > +#include <linux/ring_buffer.h>
> > +#include <linux/slab.h>
> > +#include <linux/stat.h>
> > +
> > +#include <drm/drm_device.h>
> > +#include <drm/drm_print.h>
> > +
> > +#define DRM_TRACE_MAX_LEN 256
> > +
> > +/**
> > + * DOC: DRM Tracing
> > + *
> > + * *tl;dr* DRM tracing is a lightweight alternative to traditional DRM
> > debug
> > + * logging.
> > + *
> > + * While DRM logging is quite convenient when reproducing a specific
> > issue, it
> > + * doesn't help when something goes wrong unexpectedly. There are a couple
> > + * reasons why one does not want to enable DRM logging at all times:
> > + *
> > + * 1. We don't want to overwhelm syslog with drm spam, others have to use
> > it too
> > + * 2. Console logging is slow
> > + *
> > + * DRM tracing aims to solve both these problems.
> > + *
> > + * To use DRM tracing, write a DRM debug category mask (this is a bitmask
> > of
> > + * &drm_debug_category values) to the trace_mask file:
> > + * ::
> > + *
> > + * eg: echo 0x106 > /sys/kernel/debug/dri/trace_mask
> > + *
> > + * Once active, all log messages in the specified categories will be
> > written to
> > + * the DRM trace. Once at capacity, the trace will overwrite old messages
> > with
> > + * new ones. At any point, one can read the trace file to extract the
> > previous N
> > + * DRM messages:
> > + * ::
> > + *
> > + * eg: cat /sys/kernel/debug/dri/trace
> > + *
> > + * Considerations
> > + * **************
> > + * The contents of the DRM Trace are **not** considered UABI. **DO NOT
> > depend on
> > + * the values of these traces in your userspace.** These traces are
> > intended for
> > + * entertainment purposes only. The contents of these logs carry no
> > warranty,
> > + * expressed or implied.
> > + *
> > + * New traces can not be added to the trace buffer while it is being read.
> > If
> > + * this proves to be a problem, it can be mitigated by making a copy of the
> > + * buffer on start of read. Since DRM trace is not meant to be continuously
> > + * read, this loss is acceptable.
> > + *
> > + * The timestamps on logs are CPU-local. As such, log messages from
> > different
> > + * CPUs may have slightly different ideas about time.
> > + *
> > + * Since each CPU has its own buffer, they won't all overflow at the same
> > rate.
> > + * This means that messages from a particularly active CPU could be dropped
> > + * while an inactive CPU might have much older log messages. So don't be
> > fooled
> > + * if you seem to be missing log messages when you see a switch between
> > CPUs in
> > + * the logs.
> > + *
> > + * Internals
> > + * *********
> > + * The DRM Tracing functions are intentionally unexported, they are not
> > meant to
> > + * be used by drivers directly. The reasons are twofold:
> > + *
> > + * 1. All messages going to traces should also go to the console logs. This
> > + * ensures users can choose their logging medium without fear they're
> > losing
> > + * messages.
> > + * 2. Writing directly to the trace skips category filtering, resulting in
> > trace
> > + * spam.
> > + */
> > +
> > +struct drm_trace_info {
> > + struct ring_buffer *buffer;
> > + struct dentry *debugfs;
> > + struct dentry *debugfs_mask;
> > + enum drm_debug_category category_mask;
> > +};
> > +static struct drm_trace_info drm_trace;
> > +
> > +struct drm_trace_seq_iter {
> > + loff_t pos;
> > + cpumask_var_t cpu_mask;
> > + int cpu;
> > + u64 ts;
> > +};
> > +
> > +static void *drm_trace_seq_start(struct seq_file *seq_file, loff_t *pos)
> > +{
> > + struct drm_trace_info *info = seq_file->private;
> > + struct drm_trace_seq_iter *iter;
> > + int cpu;
> > +
> > + iter = kzalloc(sizeof(*iter), GFP_KERNEL);
> > + if (!iter)
> > + return NULL;
> > +
> > + if (!zalloc_cpumask_var(&iter->cpu_mask, GFP_KERNEL))
> > + return NULL;
> > +
> > + /*
> > + * TODO: We could do better than stopping record for the entirety of the
> > + * read session.
> > + */
> > + ring_buffer_record_off(info->buffer);
> > +
> > + /*
> > + * pos is only used as a means of determining whether we're at the start
> > + * of the virtual file, or continuing a read. We don't want to skip over
> > + * log lines since that's not a meaningful thing to do.
> > + */
> > + iter->pos = *pos;
> > +
> > + iter->cpu = -1;
> > +
> > + /*
> > + * There's no way to extract the ring buffer's cpumask, so we'll try
> > + * every possible cpu and skip the invalid entries.
> > + */
> > + for_each_possible_cpu(cpu) {
> > + if (ring_buffer_entries_cpu(info->buffer, cpu))
> > + cpumask_set_cpu(cpu, iter->cpu_mask);
> > + }
> > +
> > + return iter;
> > +}
> > +
> > +static void *drm_trace_seq_next(struct seq_file *seq_file, void *data,
> > + loff_t *pos)
> > +{
> > + struct drm_trace_info *info = seq_file->private;
> > + struct drm_trace_seq_iter *iter = data;
> > + int cpu;
> > +
> > + *pos = ++iter->pos;
> > + iter->cpu = -1;
> > + iter->ts = 0;
> > +
> > + /* Find the oldest event across our cpu_mask */
> > + for_each_cpu(cpu, iter->cpu_mask) {
> > + u64 ts;
> > +
> > + if (!ring_buffer_peek(info->buffer, cpu, &ts, NULL)) {
> > + cpumask_clear_cpu(cpu, iter->cpu_mask);
> > + continue;
> > + }
> > + if (iter->cpu == -1 || ts < iter->ts) {
> > + iter->ts = ts;
> > + iter->cpu = cpu;
> > + }
> > + }
> > + if (iter->cpu == -1)
> > + return NULL;
> > +
> > + return iter;
> > +}
> > +
> > +static void drm_trace_seq_stop(struct seq_file *seq_file, void *data)
> > +{
> > + struct drm_trace_info *info = seq_file->private;
> > + struct drm_trace_seq_iter *iter = data;
> > +
> > + free_cpumask_var(iter->cpu_mask);
> > + kfree(iter);
> > +
> > + ring_buffer_record_on(info->buffer);
> > +}
> > +
> > +static int drm_trace_seq_show(struct seq_file *seq_file, void *data)
> > +{
> > + struct drm_trace_info *info = seq_file->private;
> > + struct drm_trace_seq_iter *iter = data;
> > + struct ring_buffer_event *event;
> > + u64 ts, usec;
> > +
> > + if (iter->pos == 0) {
> > + seq_printf(seq_file, "[%3s %12s] %s\n", "cpu", "timestamp",
> > + "message");
> > + return 0;
> > + } else if (iter->cpu == -1) {
> > + /* This happens when we start a session with position > 0 */
> > + return SEQ_SKIP;
> > + }
> > +
> > + event = ring_buffer_consume(info->buffer, iter->cpu, &ts, NULL);
> > +
> > + ts += 500;
> > + /* ts converts from ns->us */
> > + do_div(ts, 1000);
> > + /* ts converts from us->s */
> > + usec = do_div(ts, USEC_PER_SEC);
> > +
> > + seq_printf(seq_file, "[%3u %5llu.%06llu] %s", iter->cpu, ts, usec,
> > + (const char *)ring_buffer_event_data(event));
> > +
> > + return 0;
> > +}
> > +
> > +static const struct seq_operations drm_trace_sops = {
> > + .start = drm_trace_seq_start,
> > + .next = drm_trace_seq_next,
> > + .stop = drm_trace_seq_stop,
> > + .show = drm_trace_seq_show
> > +};
> > +
> > +static int drm_trace_fop_open(struct inode *inode, struct file *file)
> > +{
> > + struct seq_file *seq_file;
> > + int ret;
> > +
> > + ret = seq_open(file, &drm_trace_sops);
> > + if (ret)
> > + return ret;
> > +
> > + seq_file = (struct seq_file *)file->private_data;
> > + seq_file->private = inode->i_private; /* this is drm_trace_info */
> > +
> > + return 0;
> > +}
> > +
> > +static const struct file_operations drm_trace_fops = {
> > + .open = drm_trace_fop_open,
> > + .read = seq_read,
> > + .llseek = seq_lseek,
> > + .release = seq_release,
> > +};
> > +
> > +/**
> > + * drm_trace_init - initializes tracing for drm core
> > + * @debugfs_root: the dentry for drm core's debugfs root
> > + *
> > + * This function is called on drm core init. It is responsible for
> > initializing
> > + * drm tracing. This function must be matched by a call to
> > drm_trace_cleanup().
> > + *
> > + * Returns: 0 on success, -errno on failure
> > + */
> > +int drm_trace_init(struct dentry *debugfs_root)
> > +{
> > + struct drm_trace_info *info = &drm_trace;
> > + int ret;
> > +
> > + info->buffer = ring_buffer_alloc(PAGE_SIZE * 2, RB_FL_OVERWRITE);
> > + if (!info->buffer)
> > + return -ENOMEM;
> > +
> > + info->debugfs_mask = debugfs_create_u32("trace_mask",
> > + S_IFREG | S_IRUGO | S_IWUSR,
> > + debugfs_root,
> > + &info->category_mask);
> > + if (IS_ERR(info->debugfs)) {
> > + ret = PTR_ERR(info->debugfs);
> > + goto err_debugfs_mask;
> > + }
> > +
> > + info->debugfs = debugfs_create_file("trace", S_IFREG | S_IRUGO,
> > + debugfs_root, info,
> > + &drm_trace_fops);
> > + if (IS_ERR(info->debugfs)) {
> > + ret = PTR_ERR(info->debugfs);
> > + goto err_debugfs;
> > + }
> > +
> > + return 0;
> > +
> > +err_debugfs_mask:
> > + debugfs_remove(info->debugfs_mask);
> > +err_debugfs:
> > + ring_buffer_free(info->buffer);
> > + return ret;
> > +}
> > +
> > +/**
> > + * drm_trace_cleanup - cleans up tracing for drm core
> > + *
> > + * This function is responsible for cleaning up anything that was
> > previously
> > + * initialized in drm_trace_init()
> > + */
> > +void drm_trace_cleanup()
> > +{
> > + struct drm_trace_info *info = &drm_trace;
> > +
> > + debugfs_remove(info->debugfs);
> > + debugfs_remove(info->debugfs_mask);
> > + ring_buffer_free(info->buffer);
> > + memset(info, 0, sizeof(*info));
> > +}
> > +
> > +/**
> > + * drm_trace_enabled - check if a debug category has traces enabled
> > + * @category: the debug category to check
> > + *
> > + * Returns true if the given category has drm traces enabled, false
> > otherwise.
> > + */
> > +bool drm_trace_enabled(enum drm_debug_category category)
> > +{
> > + return READ_ONCE(drm_trace.category_mask) & category;
> > +}
> > +
> > +static int drm_trace_write(const void *data, unsigned int len)
> > +{
> > + struct drm_trace_info *info = &drm_trace;
> > + struct ring_buffer_event *event;
> > + void *event_body;
> > +
> > + event = ring_buffer_lock_reserve(info->buffer, len);
> > + if (!event)
> > + return -ENOMEM;
> > +
> > + event_body = ring_buffer_event_data(event);
> > + memcpy(event_body, data, len);
> > +
> > + return ring_buffer_unlock_commit(info->buffer, event);
> > +}
> > +
> > +/**
> > + * drm_trace_printf - adds an entry to the drm trace
> > + * @format: printf format of the message to add to the trace
> > + *
> > + * This function adds a new entry in the drm trace.
> > + */
> > +void drm_trace_printf(const char *format, ...)
> > +{
> > + char buf[DRM_TRACE_MAX_LEN];
> > + va_list args;
> > + int ret;
> > +
> > + va_start(args, format);
> > + ret = vsnprintf(buf, sizeof(buf), format, args);
> > + va_end(args);
> > +
> > + if (ret < 0)
> > + return;
> > + else if (ret >= sizeof(buf))
> > + ret = sizeof(buf) - 1;
> > +
> > + drm_trace_write(buf, ret + 1);
> > +}
> > +
> > +/**
> > + * drm_dev_trace_printf - adds an entry to the drm trace
> > + * @dev: pointer to device so we can print the name
> > + * @format: printf format of the message to add to the trace
> > + *
> > + * This function adds a new entry in the drm trace.
> > + */
> > +void drm_dev_trace_printf(const struct device *dev, const char *format,
> > ...)
> > +{
> > + char buf[DRM_TRACE_MAX_LEN];
> > + struct va_format vaf;
> > + va_list args;
> > + int ret;
> > +
> > + va_start(args, format);
> > + vaf.fmt = format;
> > + vaf.va = &args;
> > + ret = snprintf(buf, sizeof(buf), "%s %s: %pV", dev_driver_string(dev),
> > + dev_name(dev), &vaf);
> > + va_end(args);
> > +
> > + if (ret < 0)
> > + return;
> > + else if (ret >= sizeof(buf))
> > + ret = sizeof(buf) - 1;
> > +
> > + drm_trace_write(buf, ret + 1);
> > +}
> > diff --git a/include/drm/drm_print.h b/include/drm/drm_print.h
> > index 8f99d389792d..1f3dae7150f0 100644
> > --- a/include/drm/drm_print.h
> > +++ b/include/drm/drm_print.h
> > @@ -320,6 +320,45 @@ static inline bool drm_debug_enabled(enum
> > drm_debug_category category)
> > return unlikely(__drm_debug & category);
> > }
> >
> > +#ifdef CONFIG_DEBUG_FS
> > +
> > +int drm_trace_init(struct dentry *debugfs_root);
> > +bool drm_trace_enabled(enum drm_debug_category category);
> > +__printf(1, 2)
> > +void drm_trace_printf(const char *format, ...);
> > +__printf(2, 3)
> > +void drm_dev_trace_printf(const struct device *dev, const char *format,
> > ...);
> > +void drm_trace_cleanup(void);
> > +
> > +#else
> > +
> > +static inline int drm_trace_init(struct dentry *debugfs_root)
> > +{
> > + return 0;
> > +}
> > +
> > +static inline bool drm_trace_enabled(enum drm_debug_category category)
> > +{
> > + return false;
> > +}
> > +
> > +__printf(1, 2)
> > +static inline void drm_trace_printf(const char *format, ...)
> > +{
> > +}
> > +
> > +__printf(2, 3)
> > +static inline void drm_dev_trace_printf(const struct device *dev,
> > + const char *format, ...)
> > +{
> > +}
> > +
> > +static inline void drm_trace_cleanup(void)
> > +{
> > +}
> > +
> > +#endif
> > +
> > /*
> > * struct device based logging
> > *
>
> --
> Jani Nikula, Intel Open Source Graphics Center
--
Sean Paul, Software Engineer, Google / Chromium OS
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