[RFC 1/4] drm: Introduce drmfs pseudo filesystem interfaces

[swati.dhin...@intel.com]

From: Sourab Gupta 

The patch introduces a new pseudo filesystem type, named 'drmfs' which is
intended to house the files for the data generated by drm subsystem that
cannot be accommodated by any of the existing filesystems.
The filesystem is modelled on the lines of existing pseudo-filesystems such
as debugfs/tracefs, and borrows ideas from their implementation.
This filesystem will be appearing at sys/kernel/drm.

A new config 'CONFIG_DRMFS' is introduced to enable/disable the filesystem,
which is dependent on CONFIG_DRM.
The filesystem will not be registered standalone during kernel init time,
instead it is intended to be initialized/registered during drm initialization.

The intent for introduction of the filesystem is to act as a location to hold
various kinds of data output from Linux DRM subsystems, which can't really fit
anywhere else into the existing filesystems such as debugfs/sysfs etc. All these
filesystems have their own constraints and are intended to output a particular
type of data such as attributes and small debug parameter data. Due to these
constraints, there is a need for a new pseudo filesytem, customizable to DRM
specific requirements and catering to the needs to DRM subsystem components

Signed-off-by: Sourab Gupta 
Signed-off-by: Swati Dhingra 
---
 drivers/gpu/drm/Kconfig|   9 +
 drivers/gpu/drm/Makefile   |   1 +
 drivers/gpu/drm/drmfs.c| 555 +
 include/drm/drmfs.h|  77 +++
 include/uapi/linux/magic.h |   3 +
 5 files changed, 645 insertions(+)
 create mode 100644 drivers/gpu/drm/drmfs.c
 create mode 100644 include/drm/drmfs.h

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 95fc041..5082840 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -26,6 +26,15 @@ config DRM_MIPI_DSI
bool
depends on DRM

+config DRMFS
+   bool "Drmfs file system support"
+   depends on DRM
+   help
+ Drmfs is a pseudo file system for drm subsystem output data.
+
+ drmfs is a filesystem which serves as a stable ABI to hold
+ miscellaneous output data from drm subsystems.
+
 config DRM_DP_AUX_CHARDEV
bool "DRM DP AUX Interface"
depends on DRM
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 883f3e7..5021225 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -42,6 +42,7 @@ CFLAGS_drm_trace_points.o := -I$(src)

 obj-$(CONFIG_DRM)  += drm.o
 obj-$(CONFIG_DRM_MIPI_DSI) += drm_mipi_dsi.o
+obj-$(CONFIG_DRMFS)+= drmfs.o
 obj-$(CONFIG_DRM_ARM)  += arm/
 obj-$(CONFIG_DRM_TTM)  += ttm/
 obj-$(CONFIG_DRM_TDFX) += tdfx/
diff --git a/drivers/gpu/drm/drmfs.c b/drivers/gpu/drm/drmfs.c
new file mode 100644
index 000..bdb0e7b
--- /dev/null
+++ b/drivers/gpu/drm/drmfs.c
@@ -0,0 +1,555 @@
+/*
+ * Copyright © 2014 Intel Corporation
+ *
+ * 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 (including the next
+ * paragraph) 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 AUTHORS OR COPYRIGHT HOLDERS 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:
+ * Swati Dhingra 
+ * Sourab Gupta 
+ * Akash Goel 
+ */
+
+/*
+ * drmfs is the filesystem used for output of drm subsystem data
+ */
+
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+
+#define DRMFS_DEFAULT_MODE 0700
+
+static struct vfsmount *drmfs_mount;
+static int drmfs_mount_count;
+static bool drmfs_registered;
+
+static ssize_t default_read_file(struct file *file, char __user *buf,
+   size_t count, loff_t *ppos)
+{
+   return 0;
+}
+
+static ssize_t default_write_file(struct file *file, const char __user *buf,
+   size_t count, loff_t *ppos)
+{
+   return count;
+}
+
+static const struct file_operations drmfs_default_file_operations = {
+   .read = default_read_file,
+   .write =default_write_file,
+   .open = simple_open,
+   .llseek =   noo

[RFC 0/4] Introduce drmfs pseudo filesystem for drm subsystem

[swati.dhin...@intel.com]

From: Swati Dhingra 

Currently, we don't have a stable ABI which can be used for the purpose of
providing output debug/loggging/crc and other such data from DRM.
The ABI in current use (filesystems, ioctls, et al.) have their own
constraints and are intended to output a particular type of data.
Few cases in point:
sysfs   - stable ABI, but constrained to one textual value per file
debugfs - unstable ABI, free-for-all
ioctls  - not as suitable to many single purpose continuous data
  dumping, we would very quickly run out ioctl space; requires more
  userspace support than "cat"
device nodes -  a real possibilty, kernel instantiation is more tricky,
requires udev (+udev.rules) or userspace discovery of the
dynamic major:minor (via sysfs) [mounting a registered
filesystem is easy in comparison]
netlink - stream based, therefore involves numerous copies.

Debugfs is the lesser among the evils here, thereby we have grown used to the
convenience and flexibility in presentation that debugfs gives us
(including relayfs inodes) that we want some of that hierachy in stable user
ABI form.

Due to these limitations, there is a need for a new pseudo filesytem, that
would act as a stable 'free-for-all' ABI, with the heirarchial structure and
thus convenience of debugfs. This will be managed by drm, thus named 'drmfs'.
DRM would register this filesystem to manage a canonical mountpoint, but this
wouldn't limit everyone to only using that pseudofs underneath.

This can serve to hold various kinds of output data from Linux DRM subsystems,
for the files which can't truely fit anywhere else with existing ABI's but
present so, for the lack of a better place.

In this patch series, we have introduced a pseudo filesystem named as 'drmfs'
for now. The filesystem is introduced in the first patch, and the subsequent
patches make use of the filesystem interfaces, in drm driver, and making them
available for use by the drm subsystem components, one of which is i915.
We've moved the location of i915 GuC logs from debugfs to drmfs in the last
patch. Subsequently, more such files such as pipe_crc, error states, memory
stats, etc. can be move to this filesystem, if the idea introduced here is
acceptable per se. The filesystem introduced is being used to house the data
generated by i915 driver in this patch series, but will hopefully be generic
enough to provide scope for usage by any other drm subsystem component.

The patch series is being floated as RFC to gather feedback on the idea and
infrastructure proposed here and it's suitability to address the specific
problem statement/use case.

TODO: Create documentation. Will do so in next version.

v2: fix the bat failures caused due to missing config check

v3: Changes made:
- Move the location of drmfs from fs/ to drivers/gpu/drm/ (Chris)
- Moving config checks to header (Chris,Daniel)


Sourab Gupta (4):
  drm: Introduce drmfs pseudo filesystem interfaces
  drm: Register drmfs filesystem from drm init
  drm: Create driver specific root directory inside drmfs
  drm/i915: Creating guc log file in drmfs instead of debugfs

 drivers/gpu/drm/Kconfig|   9 +
 drivers/gpu/drm/Makefile   |   1 +
 drivers/gpu/drm/drm_drv.c  |  12 +
 drivers/gpu/drm/drmfs.c| 555 +
 drivers/gpu/drm/i915/i915_guc_submission.c |  33 +-
 include/drm/drm_drv.h  |   3 +
 include/drm/drmfs.h|  77 
 include/uapi/linux/magic.h |   3 +
 8 files changed, 672 insertions(+), 21 deletions(-)
 create mode 100644 drivers/gpu/drm/drmfs.c
 create mode 100644 include/drm/drmfs.h

-- 
2.7.4

[RFC 2/4] drm: Register drmfs filesystem from drm init

[swati.dhin...@intel.com]

From: Sourab Gupta 

The drmfs filesystem will not be registered standalone during kernel init time,
instead it is intended to be initialized/registered during drm initialization.

Signed-off-by: Sourab Gupta 
Signed-off-by: Swati Dhingra 
---
 drivers/gpu/drm/drm_drv.c | 6 ++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index f74b7d0..298013c 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -34,6 +34,7 @@
 #include 

 #include 
+#include 
 #include 

 #include "drm_crtc_internal.h"
@@ -828,6 +829,7 @@ static void drm_core_exit(void)
 {
unregister_chrdev(DRM_MAJOR, "drm");
debugfs_remove(drm_debugfs_root);
+   drmfs_fini();
drm_sysfs_destroy();
idr_destroy(&drm_minors_idr);
drm_connector_ida_destroy();
@@ -848,6 +850,10 @@ static int __init drm_core_init(void)
goto error;
}

+   ret = drmfs_init();
+   if (ret < 0)
+   DRM_ERROR("Cannot create DRM FS: %d\n", ret);
+
drm_debugfs_root = debugfs_create_dir("dri", NULL);
if (!drm_debugfs_root) {
ret = -ENOMEM;
-- 
2.7.4

[RFC 3/4] drm: Create driver specific root directory inside drmfs

[swati.dhin...@intel.com]

From: Sourab Gupta 

A driver specific directory is created inside drmfs root, and dentry of
this directory is saved for subsequent use by the driver (e.g. i915).
The driver can then create files/directories inside this root directory
directly.

In case of i915 driver, the top directory is created at '/sys/kernel/drm/i915'.

Signed-off-by: Sourab Gupta 
Signed-off-by: Swati Dhingra 
---
 drivers/gpu/drm/drm_drv.c | 6 ++
 include/drm/drm_drv.h | 3 +++
 2 files changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 298013c..4c32cf8 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -671,6 +671,11 @@ EXPORT_SYMBOL(drm_dev_unref);
 int drm_dev_register(struct drm_device *dev, unsigned long flags)
 {
int ret;
+   struct dentry *drmfs_root;
+
+   drmfs_root = drmfs_create_dir(dev->driver->name, NULL);
+   if (!IS_ERR(drmfs_root))
+   dev->driver->drmfs_root = drmfs_root;

mutex_lock(&drm_global_mutex);

@@ -742,6 +747,7 @@ void drm_dev_unregister(struct drm_device *dev)
drm_minor_unregister(dev, DRM_MINOR_PRIMARY);
drm_minor_unregister(dev, DRM_MINOR_RENDER);
drm_minor_unregister(dev, DRM_MINOR_CONTROL);
+   drmfs_remove(dev->driver->drmfs_root);
 }
 EXPORT_SYMBOL(drm_dev_unregister);

diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index c4fc495..d646296 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -405,6 +405,9 @@ struct drm_driver {

/* List of devices hanging off this driver with stealth attach. */
struct list_head legacy_dev_list;
+
+   /* drmfs parent directory dentry for this driver */
+   struct dentry *drmfs_root;
 };

 extern __printf(6, 7)
-- 
2.7.4

[RFC 4/4] drm/i915: Creating guc log file in drmfs instead of debugfs

[swati.dhin...@intel.com]

From: Sourab Gupta 

In the current scenario, the relay API fit well only with debugfs, due to
availability of parent dentry. Any other existing filesystem was not feasible 
for
holding guc logs, due to incompatibility with relay. But this makes the  guc_log
file unavailable on the production kernels.

GuC log file can therefore be one of candidates for movement to the drmfs
filesystem, which can satisfy all the requirements needed by relay API, and can
house any relayfs based output file.

The patch moves the parent directory of guc 'log_dir' from debugfs_root to
drmfs_root, while using the drmfs api's to create the requisite files.

Signed-off-by: Sourab Gupta 
Signed-off-by: Swati Dhingra 
---
 drivers/gpu/drm/i915/i915_guc_submission.c | 33 +++---
 1 file changed, 12 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c 
b/drivers/gpu/drm/i915/i915_guc_submission.c
index 5841380..3f5978a 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -22,8 +22,8 @@
  *
  */
 #include 
-#include 
 #include 
+#include 
 #include "i915_drv.h"
 #include "intel_uc.h"

@@ -812,7 +812,7 @@ static int subbuf_start_callback(struct rchan_buf *buf,
 }

 /*
- * file_create() callback. Creates relay file in debugfs.
+ * file_create() callback. Creates relay file.
  */
 static struct dentry *create_buf_file_callback(const char *filename,
   struct dentry *parent,
@@ -838,17 +838,19 @@ static struct dentry *create_buf_file_callback(const char 
*filename,
 * dentry of the file associated with the channel buffer and that file's
 * name need not be same as the filename passed as an argument.
 */
-   buf_file = debugfs_create_file("guc_log", mode,
+
+   buf_file = drmfs_create_file("guc_log", mode,
   parent, buf, &relay_file_operations);
+
return buf_file;
 }

 /*
- * file_remove() default callback. Removes relay file in debugfs.
+ * file_remove() default callback. Removes relay file.
  */
 static int remove_buf_file_callback(struct dentry *dentry)
 {
-   debugfs_remove(dentry);
+   drmfs_remove(dentry);
return 0;
 }

@@ -898,22 +900,11 @@ static int guc_log_create_relay_file(struct intel_guc 
*guc)
struct dentry *log_dir;
int ret;

-   /* For now create the log file in /sys/kernel/debug/dri/0 dir */
-   log_dir = dev_priv->drm.primary->debugfs_root;
-
-   /* If /sys/kernel/debug/dri/0 location do not exist, then debugfs is
-* not mounted and so can't create the relay file.
-* The relay API seems to fit well with debugfs only, for availing relay
-* there are 3 requirements which can be met for debugfs file only in a
-* straightforward/clean manner :-
-* i)   Need the associated dentry pointer of the file, while opening 
the
-*  relay channel.
-* ii)  Should be able to use 'relay_file_operations' fops for the file.
-* iii) Set the 'i_private' field of file's inode to the pointer of
-*  relay channel buffer.
-*/
+   /* Create the log file in drmfs dir: /sys/kernel/drm/i915/ */
+   log_dir = dev_priv->drm.driver->drmfs_root;
+
if (!log_dir) {
-   DRM_ERROR("Debugfs dir not available yet for GuC log file\n");
+   DRM_ERROR("Root dir not available yet for GuC log file\n");
return -ENODEV;
}

@@ -1154,7 +1145,7 @@ static int guc_log_create_extras(struct intel_guc *guc)
if (!guc->log.relay_chan) {
/* Create a relay channel, so that we have buffers for storing
 * the GuC firmware logs, the channel will be linked with a file
-* later on when debugfs is registered.
+* later on when drmfs is registered.
 */
ret = guc_log_create_relay_channel(guc);
if (ret)
-- 
2.7.4

[RFC 0/4] Introduce drmfs pseudo filesystem for drm subsystem

[swati.dhin...@intel.com]

From: Swati Dhingra 

Currently, we don't have a stable ABI which can be used for the purpose of
providing output debug/loggging/crc and other such data from DRM.
The ABI in current use (filesystems, ioctls, et al.) have their own
constraints and are intended to output a particular type of data.
Few cases in point:
sysfs   - stable ABI, but constrained to one textual value per file
debugfs - unstable ABI, free-for-all
ioctls  - not as suitable to many single purpose continuous data
  dumping, we would very quickly run out ioctl space; requires more
  userspace support than "cat"
device nodes -  a real possibilty, kernel instantiation is more tricky,
requires udev (+udev.rules) or userspace discovery of the
dynamic major:minor (via sysfs) [mounting a registered
filesystem is easy in comparison]
netlink - stream based, therefore involves numerous copies.

Debugfs is the lesser among the evils here, thereby we have grown used to the
convenience and flexibility in presentation that debugfs gives us
(including relayfs inodes) that we want some of that hierachy in stable user
ABI form.

Due to these limitations, there is a need for a new pseudo filesytem, that
would act as a stable 'free-for-all' ABI, with the heirarchial structure and
thus convenience of debugfs. This will be managed by drm, thus named 'drmfs'.
DRM would register this filesystem to manage a canonical mountpoint, but this
wouldn't limit everyone to only using that pseudofs underneath.

This can serve to hold various kinds of output data from Linux DRM subsystems,
for the files which can't truely fit anywhere else with existing ABI's but
present so, for the lack of a better place.

In this patch series, we have introduced a pseudo filesystem named as 'drmfs'
for now. The filesystem is introduced in the first patch, and the subsequent
patches make use of the filesystem interfaces, in drm driver, and making them
available for use by the drm subsystem components, one of which is i915.
We've moved the location of i915 GuC logs from debugfs to drmfs in the last
patch. Subsequently, more such files such as pipe_crc, error states, memory
stats, etc. can be move to this filesystem, if the idea introduced here is
acceptable per se. The filesystem introduced is being used to house the data
generated by i915 driver in this patch series, but will hopefully be generic
enough to provide scope for usage by any other drm subsystem component.

The patch series is being floated as RFC to gather feedback on the idea and
infrastructure proposed here and it's suitability to address the specific
problem statement/use case.

v2: fix the bat failures caused due to missing config check

v3: Changes made:
- Move the location of drmfs from fs/ to drivers/gpu/drm/ (Chris)
- Moving config checks to header (Chris,Daniel)

v4: Added the kernel Documentaion (using Sphinx).

Sourab Gupta (4):
  drm: Introduce drmfs pseudo filesystem interfaces
  drm: Register drmfs filesystem from drm init
  drm: Create driver specific root directory inside drmfs
  drm/i915: Creating guc log file in drmfs instead of debugfs

 Documentation/gpu/drm-uapi.rst |  76 
 drivers/gpu/drm/Kconfig|   9 +
 drivers/gpu/drm/Makefile   |   1 +
 drivers/gpu/drm/drm_drv.c  |  26 ++
 drivers/gpu/drm/drmfs.c| 566 +
 drivers/gpu/drm/i915/i915_guc_submission.c |  33 +-
 include/drm/drm_drv.h  |   3 +
 include/drm/drmfs.h|  77 
 include/uapi/linux/magic.h |   3 +
 9 files changed, 773 insertions(+), 21 deletions(-)
 create mode 100644 drivers/gpu/drm/drmfs.c
 create mode 100644 include/drm/drmfs.h

-- 
2.7.4

[RFC 3/4] drm: Create driver specific root directory inside drmfs

[swati.dhin...@intel.com]

From: Sourab Gupta 

A driver specific directory is created inside drmfs root, and dentry of
this directory is saved for subsequent use by the driver (e.g. i915).
The driver can then create files/directories inside this root directory
directly.

In case of i915 driver, the top directory is created at '/sys/kernel/drm/i915'.

Signed-off-by: Sourab Gupta 
Signed-off-by: Swati Dhingra 
---
 drivers/gpu/drm/drm_drv.c | 6 ++
 include/drm/drm_drv.h | 3 +++
 2 files changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 298013c..4c32cf8 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -671,6 +671,11 @@ EXPORT_SYMBOL(drm_dev_unref);
 int drm_dev_register(struct drm_device *dev, unsigned long flags)
 {
int ret;
+   struct dentry *drmfs_root;
+
+   drmfs_root = drmfs_create_dir(dev->driver->name, NULL);
+   if (!IS_ERR(drmfs_root))
+   dev->driver->drmfs_root = drmfs_root;

mutex_lock(&drm_global_mutex);

@@ -742,6 +747,7 @@ void drm_dev_unregister(struct drm_device *dev)
drm_minor_unregister(dev, DRM_MINOR_PRIMARY);
drm_minor_unregister(dev, DRM_MINOR_RENDER);
drm_minor_unregister(dev, DRM_MINOR_CONTROL);
+   drmfs_remove(dev->driver->drmfs_root);
 }
 EXPORT_SYMBOL(drm_dev_unregister);

diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index c4fc495..d646296 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -405,6 +405,9 @@ struct drm_driver {

/* List of devices hanging off this driver with stealth attach. */
struct list_head legacy_dev_list;
+
+   /* drmfs parent directory dentry for this driver */
+   struct dentry *drmfs_root;
 };

 extern __printf(6, 7)
-- 
2.7.4

[RFC 4/4] drm/i915: Creating guc log file in drmfs instead of debugfs

[swati.dhin...@intel.com]

From: Sourab Gupta 

In the current scenario, the relay API fit well only with debugfs, due to
availability of parent dentry. Any other existing filesystem was not feasible 
for
holding guc logs, due to incompatibility with relay. But this makes the  guc_log
file unavailable on the production kernels.

GuC log file can therefore be one of candidates for movement to the drmfs
filesystem, which can satisfy all the requirements needed by relay API, and can
house any relayfs based output file.

The patch moves the parent directory of guc 'log_dir' from debugfs_root to
drmfs_root, while using the drmfs api's to create the requisite files.

Signed-off-by: Sourab Gupta 
Signed-off-by: Swati Dhingra 
---
 drivers/gpu/drm/i915/i915_guc_submission.c | 33 +++---
 1 file changed, 12 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c 
b/drivers/gpu/drm/i915/i915_guc_submission.c
index 5841380..3f5978a 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -22,8 +22,8 @@
  *
  */
 #include 
-#include 
 #include 
+#include 
 #include "i915_drv.h"
 #include "intel_uc.h"

@@ -812,7 +812,7 @@ static int subbuf_start_callback(struct rchan_buf *buf,
 }

 /*
- * file_create() callback. Creates relay file in debugfs.
+ * file_create() callback. Creates relay file.
  */
 static struct dentry *create_buf_file_callback(const char *filename,
   struct dentry *parent,
@@ -838,17 +838,19 @@ static struct dentry *create_buf_file_callback(const char 
*filename,
 * dentry of the file associated with the channel buffer and that file's
 * name need not be same as the filename passed as an argument.
 */
-   buf_file = debugfs_create_file("guc_log", mode,
+
+   buf_file = drmfs_create_file("guc_log", mode,
   parent, buf, &relay_file_operations);
+
return buf_file;
 }

 /*
- * file_remove() default callback. Removes relay file in debugfs.
+ * file_remove() default callback. Removes relay file.
  */
 static int remove_buf_file_callback(struct dentry *dentry)
 {
-   debugfs_remove(dentry);
+   drmfs_remove(dentry);
return 0;
 }

@@ -898,22 +900,11 @@ static int guc_log_create_relay_file(struct intel_guc 
*guc)
struct dentry *log_dir;
int ret;

-   /* For now create the log file in /sys/kernel/debug/dri/0 dir */
-   log_dir = dev_priv->drm.primary->debugfs_root;
-
-   /* If /sys/kernel/debug/dri/0 location do not exist, then debugfs is
-* not mounted and so can't create the relay file.
-* The relay API seems to fit well with debugfs only, for availing relay
-* there are 3 requirements which can be met for debugfs file only in a
-* straightforward/clean manner :-
-* i)   Need the associated dentry pointer of the file, while opening 
the
-*  relay channel.
-* ii)  Should be able to use 'relay_file_operations' fops for the file.
-* iii) Set the 'i_private' field of file's inode to the pointer of
-*  relay channel buffer.
-*/
+   /* Create the log file in drmfs dir: /sys/kernel/drm/i915/ */
+   log_dir = dev_priv->drm.driver->drmfs_root;
+
if (!log_dir) {
-   DRM_ERROR("Debugfs dir not available yet for GuC log file\n");
+   DRM_ERROR("Root dir not available yet for GuC log file\n");
return -ENODEV;
}

@@ -1154,7 +1145,7 @@ static int guc_log_create_extras(struct intel_guc *guc)
if (!guc->log.relay_chan) {
/* Create a relay channel, so that we have buffers for storing
 * the GuC firmware logs, the channel will be linked with a file
-* later on when debugfs is registered.
+* later on when drmfs is registered.
 */
ret = guc_log_create_relay_channel(guc);
if (ret)
-- 
2.7.4

[RFC 1/4] drm: Introduce drmfs pseudo filesystem interfaces

[swati.dhin...@intel.com]

From: Sourab Gupta 

The patch introduces a new pseudo filesystem type, named 'drmfs' which is
intended to house the files for the data generated by drm subsystem that
cannot be accommodated by any of the existing filesystems.
The filesystem is modelled on the lines of existing pseudo-filesystems such
as debugfs/tracefs, and borrows ideas from their implementation.
This filesystem will be appearing at sys/kernel/drm.

A new config 'CONFIG_DRMFS' is introduced to enable/disable the filesystem,
which is dependent on CONFIG_DRM.
The filesystem will not be registered standalone during kernel init time,
instead it is intended to be initialized/registered during drm initialization.

The intent for introduction of the filesystem is to act as a location to hold
various kinds of data output from Linux DRM subsystems, which can't really fit
anywhere else into the existing filesystems such as debugfs/sysfs etc. All these
filesystems have their own constraints and are intended to output a particular
type of data such as attributes and small debug parameter data. Due to these
constraints, there is a need for a new pseudo filesytem, customizable to DRM
specific requirements and catering to the needs to DRM subsystem components

Signed-off-by: Sourab Gupta 
Signed-off-by: Swati Dhingra 
---
 Documentation/gpu/drm-uapi.rst |  76 ++
 drivers/gpu/drm/Kconfig|   9 +
 drivers/gpu/drm/Makefile   |   1 +
 drivers/gpu/drm/drmfs.c| 566 +
 include/drm/drmfs.h|  77 ++
 include/uapi/linux/magic.h |   3 +
 6 files changed, 732 insertions(+)
 create mode 100644 drivers/gpu/drm/drmfs.c
 create mode 100644 include/drm/drmfs.h

diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst
index de3ac9f..be9540c 100644
--- a/Documentation/gpu/drm-uapi.rst
+++ b/Documentation/gpu/drm-uapi.rst
@@ -222,3 +222,79 @@ Testing and validation

 .. kernel-doc:: drivers/gpu/drm/drm_debugfs_crc.c
:doc: CRC ABI
+
+DRMFS
+=
+
+Overview
+
+
+Drmfs is stable ABI for housing data generated by drm subsystem components.
+
+The ABI in current use (debugfs/sysfs/ioctls) have their own constraints and
+are designed to output their own particular data types.
+
+Few cases in point::
+
+   sysfs   - stable ABI, but constrained to one textual value per file
+   debugfs - unstable ABI, free-for-all
+   ioctls  - not as suitable to many single purpose continuous data
+ dumping, we would very quickly run out ioctl space; require
+ more userspace support than "cat"
+   device nodes -  a real possibilty, kernel instantiation is more tricky,
+   requires udev (+udev.rules) or userspace discovery of
+   the dynamic major:minor (via sysfs) [mounting a
+   registered filesystem is easy in comparison]
+   netlink - stream based, therefore involves numerous copies
+
+Debugfs is the lesser among the evils here, thereby we have grown used to the
+convenience and flexibility in presentation that debugfs gives us (including
+relayfs inodes) that we want some of that hierarchy in stable user ABI form.
+
+Due to these limitations, a new pseudo filesytem is needed that would act as a
+stable ‘free-for-all’ ABI, with the heirarchial structure and thus provide
+convenience of debugfs. This to be managed by drm, thus named **drmfs**. The
+filesystem is modelled on the lines of existing pseudo-filesystems such as
+debugfs/tracefs, and borrows ideas from their implementation. DRM would 
register
+this filesystem to manage a canonical mountpoint, but this wouldn’t limit
+everyone to only use that pseudofs underneath.
+
+One of the usecase is to hold the GuC (micro-controller) logs.Currently, 
relayfs
+is being used to provide these logs to userspace. Relayfs needs a parent dentry
+to be associated with log file, and also these logs should be available in 
+production kernels. In absence of any other suitable candidate, debugfs is 
used 
+currently, since it provides the hierarchial VFS structures available (dentry 
et al.).
+Instead, drmfs provides a suitable stable ABI for GuC logs, which is modelled 
on
+the lines of debugfs but controlled fully by drm.
+
+This can serve to hold various kinds of output data from Linux DRM subsystems,
+for the files which can’t truly fit anywhere else with existing ABI’s but 
present
+so, for the lack of a better place. For e.g. i915 GuC logs, pipe_crc, error
+states, memory stats.
+
+Interfaces
+--
+
+This section covers the infrastructure of drmfs pseudo filesystem. It 
introduces
+interfaces to create/remove files and directories.
+
+.. kernel-doc:: drivers/gpu/drm/drmfs.c
+   :functions: drmfs_create_file
+
+.. kernel-doc:: drivers/gpu/drm/drmfs.c
+   :functions: drmfs_create_dir
+
+.. kernel-doc:: drivers/gpu/drm/drmfs.c
+   :functions: drmfs_remove
+
+.. kernel-doc:: drivers/gpu/drm/drmfs.c
+   :functions:

[RFC 2/4] drm: Register drmfs filesystem from drm init

[swati.dhin...@intel.com]

From: Sourab Gupta 

The drmfs filesystem will not be registered standalone during kernel init time,
instead it is intended to be initialized/registered during drm initialization.
This again is dependent on CONFIG_DRMFS being defined.

Signed-off-by: Sourab Gupta 
Signed-off-by: Swati Dhingra 
---
 drivers/gpu/drm/drm_drv.c | 6 ++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index f74b7d0..298013c 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -34,6 +34,7 @@
 #include 

 #include 
+#include 
 #include 

 #include "drm_crtc_internal.h"
@@ -828,6 +829,7 @@ static void drm_core_exit(void)
 {
unregister_chrdev(DRM_MAJOR, "drm");
debugfs_remove(drm_debugfs_root);
+   drmfs_fini();
drm_sysfs_destroy();
idr_destroy(&drm_minors_idr);
drm_connector_ida_destroy();
@@ -848,6 +850,10 @@ static int __init drm_core_init(void)
goto error;
}

+   ret = drmfs_init();
+   if (ret < 0)
+   DRM_ERROR("Cannot create DRM FS: %d\n", ret);
+
drm_debugfs_root = debugfs_create_dir("dri", NULL);
if (!drm_debugfs_root) {
ret = -ENOMEM;
-- 
2.7.4