[Intel-gfx] [PATCH v2 1/4] dri: do not check for NULL debugfs dentry

[Nirmoy Das]

Debugfs APIs returns encoded error on failure instead of NULL
and for drm primary/minor debugfs directories, we save the
returned value in the dentry pointer and pass it on to drm
drivers to further create debugfs files/directories. Error
conditions are handled by debugfs APIs, so no need to check
for NULL, as saved dentry pointers will either contain a
valid pointer or an error code.

Also document this for future reference.

CC: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
CC: Maxime Ripard <mripard at kernel.org>
CC: Thomas Zimmermann <tzimmermann at suse.de>
CC: David Airlie <airlied at linux.ie>
CC: Daniel Vetter <daniel at ffwll.ch>

Signed-off-by: Nirmoy Das <nirmoy.das at amd.com>
---
 drivers/gpu/drm/drm_debugfs.c |  9 ---------
 drivers/gpu/drm/drm_drv.c     |  1 +
 include/drm/drm_file.h        | 28 ++++++++++++++++++++++++----
 3 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
index b0a826489488..0073854a4383 100644
--- a/drivers/gpu/drm/drm_debugfs.c
+++ b/drivers/gpu/drm/drm_debugfs.c
@@ -272,9 +272,6 @@ static void drm_debugfs_remove_all_files(struct drm_minor *minor)

 void drm_debugfs_cleanup(struct drm_minor *minor)
 {
-	if (!minor->debugfs_root)
-		return;
-
 	drm_debugfs_remove_all_files(minor);

 	debugfs_remove_recursive(minor->debugfs_root);
@@ -419,9 +416,6 @@ void drm_debugfs_connector_add(struct drm_connector *connector)
 	struct drm_minor *minor = connector->dev->primary;
 	struct dentry *root;

-	if (!minor->debugfs_root)
-		return;
-
 	root = debugfs_create_dir(connector->name, minor->debugfs_root);
 	connector->debugfs_entry = root;

@@ -440,9 +434,6 @@ void drm_debugfs_connector_add(struct drm_connector *connector)

 void drm_debugfs_connector_remove(struct drm_connector *connector)
 {
-	if (!connector->debugfs_entry)
-		return;
-
 	debugfs_remove_recursive(connector->debugfs_entry);

 	connector->debugfs_entry = NULL;
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 7a5097467ba5..918f302d9c43 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -64,6 +64,7 @@ static struct idr drm_minors_idr;
  */
 static bool drm_core_init_complete;

+/* Do not deference this pointer as it will contain ERR_PTR on error. */
 static struct dentry *drm_debugfs_root;

 DEFINE_STATIC_SRCU(drm_unplug_srcu);
diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
index a3acb7ac3550..3a30fc4d8905 100644
--- a/include/drm/drm_file.h
+++ b/include/drm/drm_file.h
@@ -69,15 +69,35 @@ enum drm_minor_type {
  */
 struct drm_minor {
 	/* private: */
-	int index;			/* Minor device number */
-	int type;                       /* Control or render */
-	struct device *kdev;		/* Linux device */
+	/** @index: minor device number. */
+	int index;
+
+	/** @type: minor device type: primary, control, render. */
+	int type;
+
+	/** @kdev: Linux device pointer. */
+	struct device *kdev;
+
+	/** @dev: drm device pointer. */
 	struct drm_device *dev;

+
+	/** @debugfs_root:
+	 *
+	 * Dentry for /sys/kernel/debug/dri/@index debugfs dir. Do not
+	 * deference this pointer as it will contain ERR_PTR on error.
+	 */
 	struct dentry *debugfs_root;

+	/** @debugfs_list:
+	 *
+	 * A list to keep track of debugfs dentries created using
+	 * drm_debugfs_create_files() by drm drivers.
+	 */
 	struct list_head debugfs_list;
-	struct mutex debugfs_lock; /* Protects debugfs_list. */
+
+	/** @debugfs_lock: Protects debugfs_list. */
+	struct mutex debugfs_lock;
 };

 /**
--
2.32.0