drm/debugfs: create device-centered debugfs functions

Introduce the ability to track requests for the addition of DRM debugfs
files at any time and have them added all at once during
drm_dev_register().

Drivers can add DRM debugfs files to a device-managed list and, during
drm_dev_register(), all added files will be created at once.

Now, the drivers can use the functions drm_debugfs_add_file() and
drm_debugfs_add_files() to create DRM debugfs files instead of using the
drm_debugfs_create_files() function.

Co-developed-by: Wambui Karuga <wambui.karugax@gmail.com>
Signed-off-by: Wambui Karuga <wambui.karugax@gmail.com>
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Melissa Wen <mwen@igalia.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maíra Canal <mairacanal@riseup.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20221219120621.15086-2-mcanal@igalia.com

drivers/gpu/drm/drm_debugfs.c

@@ -38,6 +38,7 @@
 #include <drm/drm_edid.h>
 #include <drm/drm_file.h>
 #include <drm/drm_gem.h>
+#include <drm/drm_managed.h>
 
 #include "drm_crtc_internal.h"
 #include "drm_internal.h"
@@ -151,6 +152,21 @@ static int drm_debugfs_open(struct inode *inode, struct file *file)
 	return single_open(file, node->info_ent->show, node);
 }
 
+static int drm_debugfs_entry_open(struct inode *inode, struct file *file)
+{
+	struct drm_debugfs_entry *entry = inode->i_private;
+	struct drm_debugfs_info *node = &entry->file;
+
+	return single_open(file, node->show, entry);
+}
+
+static const struct file_operations drm_debugfs_entry_fops = {
+	.owner = THIS_MODULE,
+	.open = drm_debugfs_entry_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
 
 static const struct file_operations drm_debugfs_fops = {
 	.owner = THIS_MODULE,
@@ -207,6 +223,7 @@ int drm_debugfs_init(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);
@@ -230,6 +247,12 @@ int drm_debugfs_init(struct drm_minor *minor, int minor_id,
 	if (dev->driver->debugfs_init)
 		dev->driver->debugfs_init(minor);
 
+	list_for_each_entry_safe(entry, tmp, &dev->debugfs_list, list) {
+		debugfs_create_file(entry->file.name, S_IFREG | S_IRUGO,
+				    minor->debugfs_root, entry, &drm_debugfs_entry_fops);
+		list_del(&entry->list);
+	}
+
 	return 0;
 }
 
@@ -281,6 +304,53 @@ void drm_debugfs_cleanup(struct drm_minor *minor)
 	minor->debugfs_root = NULL;
 }
 
+/**
+ * drm_debugfs_add_file - Add a given file to the DRM device debugfs file list
+ * @dev: drm device for the ioctl
+ * @name: debugfs file name
+ * @show: show callback
+ * @data: driver-private data, should not be device-specific
+ *
+ * Add a given file entry to the DRM device debugfs file list to be created on
+ * drm_debugfs_init.
+ */
+void drm_debugfs_add_file(struct drm_device *dev, const char *name,
+			  int (*show)(struct seq_file*, void*), void *data)
+{
+	struct drm_debugfs_entry *entry = drmm_kzalloc(dev, sizeof(*entry), GFP_KERNEL);
+
+	if (!entry)
+		return;
+
+	entry->file.name = name;
+	entry->file.show = show;
+	entry->file.data = data;
+	entry->dev = dev;
+
+	mutex_lock(&dev->debugfs_mutex);
+	list_add(&entry->list, &dev->debugfs_list);
+	mutex_unlock(&dev->debugfs_mutex);
+}
+EXPORT_SYMBOL(drm_debugfs_add_file);
+
+/**
+ * drm_debugfs_add_files - Add an array of files to the DRM device debugfs file list
+ * @dev: drm device for the ioctl
+ * @files: The array of files to create
+ * @count: The number of files given
+ *
+ * Add a given set of debugfs files represented by an array of
+ * &struct drm_debugfs_info in the DRM device debugfs file list.
+ */
+void drm_debugfs_add_files(struct drm_device *dev, const struct drm_debugfs_info *files, int count)
+{
+	int i;
+
+	for (i = 0; i < count; i++)
+		drm_debugfs_add_file(dev, files[i].name, files[i].show, files[i].data);
+}
+EXPORT_SYMBOL(drm_debugfs_add_files);
+
 static int connector_show(struct seq_file *m, void *data)
 {
 	struct drm_connector *connector = m->private;

drivers/gpu/drm/drm_drv.c

@@ -575,6 +575,7 @@ 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);
 }
 
@@ -608,12 +609,14 @@ 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)

include/drm/drm_debugfs.h

@@ -79,12 +79,43 @@ struct drm_info_node {
 	struct dentry *dent;
 };
 
+/**
+ * struct drm_debugfs_info - debugfs info list entry
+ *
+ * This structure represents a debugfs file to be created by the drm
+ * core.
+ */
+struct drm_debugfs_info {
+	const char *name;
+	int (*show)(struct seq_file*, void*);
+	u32 driver_features;
+	void *data;
+};
+
+/**
+ * struct drm_debugfs_entry - Per-device debugfs node structure
+ *
+ * This structure represents a debugfs file, as an instantiation of a &struct
+ * drm_debugfs_info on a &struct drm_device.
+ */
+struct drm_debugfs_entry {
+	struct drm_device *dev;
+	struct drm_debugfs_info file;
+	struct list_head list;
+};
+
 #if defined(CONFIG_DEBUG_FS)
 void drm_debugfs_create_files(const struct drm_info_list *files,
 			      int count, struct dentry *root,
 			      struct drm_minor *minor);
 int drm_debugfs_remove_files(const struct drm_info_list *files,
 			     int count, struct drm_minor *minor);
+
+void drm_debugfs_add_file(struct drm_device *dev, const char *name,
+			  int (*show)(struct seq_file*, void*), void *data);
+
+void drm_debugfs_add_files(struct drm_device *dev,
+			   const struct drm_debugfs_info *files, int count);
 #else
 static inline void drm_debugfs_create_files(const struct drm_info_list *files,
 					    int count, struct dentry *root,
@@ -96,6 +127,16 @@ static inline int drm_debugfs_remove_files(const struct drm_info_list *files,
 {
 	return 0;
 }
+
+static inline void drm_debugfs_add_file(struct drm_device *dev, const char *name,
+					int (*show)(struct seq_file*, void*),
+					void *data)
+{}
+
+static inline void drm_debugfs_add_files(struct drm_device *dev,
+					 const struct drm_debugfs_info *files,
+					 int count)
+{}
 #endif
 
 #endif /* _DRM_DEBUGFS_H_ */

include/drm/drm_device.h

@@ -295,6 +295,21 @@ struct drm_device {
 	 */
 	struct drm_fb_helper *fb_helper;
 
+	/**
+	 * @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)