drm/debugfs: remove dev->debugfs_list and debugfs_mutex v2

The mutex was completely pointless in the first place since any
parallel adding of files to this list would result in random
behavior since the list is filled and consumed multiple times.

Completely drop that approach and just create the files directly but
return -ENODEV while opening the file when the minors are not
registered yet.

v2: rebase on debugfs directory rework, limit access before minors are
    registered.
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230829110115.3442-5-christian.koenig@amd.comReviewed-by: Andi Shyti <andi.shyti@linux.intel.com>

drivers/gpu/drm/drm_debugfs.c

@@ -308,7 +308,6 @@ int drm_debugfs_register(struct drm_minor *minor, int minor_id,
 			 struct dentry *root)
 {
 	struct drm_device *dev = minor->dev;
-	struct drm_debugfs_entry *entry, *tmp;
 	char name[64];
 
 	INIT_LIST_HEAD(&minor->debugfs_list);
@@ -323,30 +322,9 @@ int drm_debugfs_register(struct drm_minor *minor, int minor_id,
 	if (dev->driver->debugfs_init && dev->render != minor)
 		dev->driver->debugfs_init(minor);
 
-	list_for_each_entry_safe(entry, tmp, &dev->debugfs_list, list) {
-		debugfs_create_file(entry->file.name, 0444,
-				    minor->debugfs_root, entry, &drm_debugfs_entry_fops);
-		list_del(&entry->list);
-	}
-
 	return 0;
 }
 
-void drm_debugfs_late_register(struct drm_device *dev)
-{
-	struct drm_minor *minor = dev->primary;
-	struct drm_debugfs_entry *entry, *tmp;
-
-	if (!minor)
-		return;
-
-	list_for_each_entry_safe(entry, tmp, &dev->debugfs_list, list) {
-		debugfs_create_file(entry->file.name, 0444,
-				    minor->debugfs_root, entry, &drm_debugfs_entry_fops);
-		list_del(&entry->list);
-	}
-}
-
 int drm_debugfs_remove_files(const struct drm_info_list *files, int count,
 			     struct drm_minor *minor)
 {
@@ -416,9 +394,8 @@ void drm_debugfs_add_file(struct drm_device *dev, const char *name,
 	entry->file.data = data;
 	entry->dev = dev;
 
-	mutex_lock(&dev->debugfs_mutex);
-	list_add(&entry->list, &dev->debugfs_list);
-	mutex_unlock(&dev->debugfs_mutex);
+	debugfs_create_file(name, 0444, dev->debugfs_root, entry,
+			    &drm_debugfs_entry_fops);
 }
 EXPORT_SYMBOL(drm_debugfs_add_file);
 

drivers/gpu/drm/drm_drv.c

@@ -597,7 +597,6 @@ static void drm_dev_init_release(struct drm_device *dev, void *res)
 	mutex_destroy(&dev->clientlist_mutex);
 	mutex_destroy(&dev->filelist_mutex);
 	mutex_destroy(&dev->struct_mutex);
-	mutex_destroy(&dev->debugfs_mutex);
 	drm_legacy_destroy_members(dev);
 }
 
@@ -638,14 +637,12 @@ static int drm_dev_init(struct drm_device *dev,
 	INIT_LIST_HEAD(&dev->filelist_internal);
 	INIT_LIST_HEAD(&dev->clientlist);
 	INIT_LIST_HEAD(&dev->vblank_event_list);
-	INIT_LIST_HEAD(&dev->debugfs_list);
 
 	spin_lock_init(&dev->event_lock);
 	mutex_init(&dev->struct_mutex);
 	mutex_init(&dev->filelist_mutex);
 	mutex_init(&dev->clientlist_mutex);
 	mutex_init(&dev->master_mutex);
-	mutex_init(&dev->debugfs_mutex);
 
 	ret = drmm_add_action_or_reset(dev, drm_dev_init_release, NULL);
 	if (ret)

drivers/gpu/drm/drm_internal.h

@@ -185,7 +185,6 @@ void drm_debugfs_dev_register(struct drm_device *dev);
 int drm_debugfs_register(struct drm_minor *minor, int minor_id,
 			 struct dentry *root);
 void drm_debugfs_cleanup(struct drm_minor *minor);
-void drm_debugfs_late_register(struct drm_device *dev);
 void drm_debugfs_connector_add(struct drm_connector *connector);
 void drm_debugfs_connector_remove(struct drm_connector *connector);
 void drm_debugfs_crtc_add(struct drm_crtc *crtc);
@@ -210,10 +209,6 @@ static inline void drm_debugfs_cleanup(struct drm_minor *minor)
 {
 }
 
-static inline void drm_debugfs_late_register(struct drm_device *dev)
-{
-}
-
 static inline void drm_debugfs_connector_add(struct drm_connector *connector)
 {
 }

drivers/gpu/drm/drm_mode_config.c

@@ -54,8 +54,6 @@ int drm_modeset_register_all(struct drm_device *dev)
 	if (ret)
 		goto err_connector;
 
-	drm_debugfs_late_register(dev);
-
 	return 0;
 
 err_connector:

include/drm/drm_device.h

@@ -318,21 +318,6 @@ struct drm_device {
 	 */
 	struct dentry *debugfs_root;
 
-	/**
-	 * @debugfs_mutex:
-	 *
-	 * Protects &debugfs_list access.
-	 */
-	struct mutex debugfs_mutex;
-
-	/**
-	 * @debugfs_list:
-	 *
-	 * List of debugfs files to be created by the DRM device. The files
-	 * must be added during drm_dev_register().
-	 */
-	struct list_head debugfs_list;
-
 	/* Everything below here is for legacy driver, never use! */
 	/* private: */
 #if IS_ENABLED(CONFIG_DRM_LEGACY)