[RFC PATCH 1/3] drm/debugfs: create debugfs files during drm_dev_register().

[Wambui Karuga <wambui.karugax@gmail.com>]

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 file requests to a new list tied to drm_device.
During drm_dev_register(), the new function drm_debugfs_create_file()
will iterate over the list of added files on a given minor to create
them.

Two new structs are introduced in this change: struct drm_simple_info
which represents a drm debugfs file entry and struct
drm_simple_info_entry which is used to track file requests and is the
main parameter of choice passed by functions. Each drm_simple_info_entry is
added to the new struct drm_device->debugfs_list for file requests.

Signed-off-by: Wambui Karuga <wambui.karugax@gmail.com>
---
 drivers/gpu/drm/drm_debugfs.c | 59 ++++++++++++++++++++++++++++++++---
 drivers/gpu/drm/drm_drv.c     |  2 ++
 include/drm/drm_debugfs.h     | 38 ++++++++++++++++++++++
 include/drm/drm_device.h      | 12 +++++++
 4 files changed, 107 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
index 2bea22130703..03b0588ede68 100644
--- a/drivers/gpu/drm/drm_debugfs.c
+++ b/drivers/gpu/drm/drm_debugfs.c
@@ -145,9 +145,10 @@ static const struct drm_info_list drm_debugfs_list[] = {
 
 static int drm_debugfs_open(struct inode *inode, struct file *file)
 {
-	struct drm_info_node *node = inode->i_private;
+	struct drm_simple_info_entry *entry = inode->i_private;
+	struct drm_simple_info *node = &entry->file;
 
-	return single_open(file, node->info_ent->show, node);
+	return single_open(file, node->show_fn, entry);
 }
 
 
@@ -159,6 +160,25 @@ static const struct file_operations drm_debugfs_fops = {
 	.release = single_release,
 };
 
+/**
+ * drm_debugfs_create_file - create DRM debugfs file.
+ * @dev: drm_device that the file belongs to
+ *
+ * Create a DRM debugfs file from the list of files to be created
+ * from dev->debugfs_list.
+ */
+static void drm_debugfs_create_file(struct drm_minor *minor)
+{
+	struct drm_device *dev = minor->dev;
+	struct drm_simple_info_entry *entry;
+
+	list_for_each_entry(entry, &dev->debugfs_list, list) {
+		debugfs_create_file(entry->file.name,
+				    S_IFREG | S_IRUGO, minor->debugfs_root,
+				    entry,
+				    &drm_debugfs_fops);
+	}
+}
 
 /**
  * drm_debugfs_create_files - Initialize a given set of debugfs files for DRM
@@ -213,8 +233,7 @@ int drm_debugfs_init(struct drm_minor *minor, int minor_id,
 	sprintf(name, "%d", minor_id);
 	minor->debugfs_root = debugfs_create_dir(name, root);
 
-	drm_debugfs_create_files(drm_debugfs_list, DRM_DEBUGFS_ENTRIES,
-				 minor->debugfs_root, minor);
+	drm_debugfs_create_file(minor);
 
 	if (drm_drv_uses_atomic_modeset(dev)) {
 		drm_atomic_debugfs_init(minor);
@@ -449,4 +468,36 @@ void drm_debugfs_crtc_remove(struct drm_crtc *crtc)
 	crtc->debugfs_entry = NULL;
 }
 
+void drm_debugfs_add_file(struct drm_device *dev, const char *name,
+			  drm_simple_show_t show_fn, void *data)
+{
+	struct drm_simple_info_entry *entry =
+		kzalloc(sizeof(*entry), GFP_KERNEL);
+
+	if (!entry)
+		return;
+
+	entry->file.name = name;
+	entry->file.show_fn = show_fn;
+	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);
+
+void drm_debugfs_add_files(struct drm_device *dev,
+			   const struct drm_simple_info *files, int count)
+{
+	int i;
+
+	for (i = 0; i < count; i++) {
+		drm_debugfs_add_file(dev, files[i].name, files[i].show_fn,
+				     files[i].data);
+	}
+}
+EXPORT_SYMBOL(drm_debugfs_add_files);
+
 #endif /* CONFIG_DEBUG_FS */
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index bc38322f306e..c68df4e31aa0 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -646,12 +646,14 @@ 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(dev, drm_dev_init_release, NULL);
 	if (ret)
diff --git a/include/drm/drm_debugfs.h b/include/drm/drm_debugfs.h
index 2188dc83957f..bbce580c3b38 100644
--- a/include/drm/drm_debugfs.h
+++ b/include/drm/drm_debugfs.h
@@ -34,6 +34,44 @@
 
 #include <linux/types.h>
 #include <linux/seq_file.h>
+
+struct drm_device;
+
+typedef int (*drm_simple_show_t)(struct seq_file *, void *);
+
+/**
+ * struct drm_simple_info - debugfs file entry
+ *
+ * This struct represents a debugfs file to be created.
+ */
+struct drm_simple_info {
+	const char *name;
+	drm_simple_show_t show_fn;
+	u32 driver_features;
+	void *data;
+};
+
+/**
+ * struct drm_simple_info_entry - debugfs list entry
+ *
+ * This struct is used in tracking requests for new debugfs files
+ * to be created.
+ */
+struct drm_simple_info_entry {
+	struct drm_device *dev;
+	struct drm_simple_info file;
+	struct list_head list;
+};
+
+void drm_debugfs_add_file(struct drm_device *dev,
+			  const char *name,
+			  drm_simple_show_t show_fn,
+			  void *data);
+
+void drm_debugfs_add_files(struct drm_device *dev,
+			   const struct drm_simple_info *files,
+			   int count);
+
 /**
  * struct drm_info_list - debugfs info list entry
  *
diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
index a55874db9dd4..b84dfdac27b7 100644
--- a/include/drm/drm_device.h
+++ b/include/drm/drm_device.h
@@ -326,6 +326,18 @@ 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 add.
+	 * Files are 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)
-- 
2.26.2