media: v4l2-async: Discourage use of v4l2_async_notifier_add_subdev

Most -if not all- use-cases are expected to be covered by one of:
v4l2_async_notifier_add_fwnode_subdev,
v4l2_async_notifier_add_fwnode_remote_subdev or
v4l2_async_notifier_add_i2c_subdev.

We'd like to discourage drivers from using v4l2_async_notifier_add_subdev,
so rename it as __v4l2_async_notifier_add_subdev. This is
typically a good hint for drivers to avoid using the function.
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/v4l2-core/v4l2-async.c

@@ -611,7 +611,7 @@ void v4l2_async_notifier_cleanup(struct v4l2_async_notifier *notifier)
 }
 EXPORT_SYMBOL_GPL(v4l2_async_notifier_cleanup);
 
-int v4l2_async_notifier_add_subdev(struct v4l2_async_notifier *notifier,
+int __v4l2_async_notifier_add_subdev(struct v4l2_async_notifier *notifier,
 				   struct v4l2_async_subdev *asd)
 {
 	int ret;
@@ -628,7 +628,7 @@ int v4l2_async_notifier_add_subdev(struct v4l2_async_notifier *notifier,
 	mutex_unlock(&list_lock);
 	return ret;
 }
-EXPORT_SYMBOL_GPL(v4l2_async_notifier_add_subdev);
+EXPORT_SYMBOL_GPL(__v4l2_async_notifier_add_subdev);
 
 struct v4l2_async_subdev *
 v4l2_async_notifier_add_fwnode_subdev(struct v4l2_async_notifier *notifier,
@@ -645,7 +645,7 @@ v4l2_async_notifier_add_fwnode_subdev(struct v4l2_async_notifier *notifier,
 	asd->match_type = V4L2_ASYNC_MATCH_FWNODE;
 	asd->match.fwnode = fwnode_handle_get(fwnode);
 
-	ret = v4l2_async_notifier_add_subdev(notifier, asd);
+	ret = __v4l2_async_notifier_add_subdev(notifier, asd);
 	if (ret) {
 		fwnode_handle_put(fwnode);
 		kfree(asd);
@@ -695,7 +695,7 @@ v4l2_async_notifier_add_i2c_subdev(struct v4l2_async_notifier *notifier,
 	asd->match.i2c.adapter_id = adapter_id;
 	asd->match.i2c.address = address;
 
-	ret = v4l2_async_notifier_add_subdev(notifier, asd);
+	ret = __v4l2_async_notifier_add_subdev(notifier, asd);
 	if (ret) {
 		kfree(asd);
 		return ERR_PTR(ret);

drivers/media/v4l2-core/v4l2-fwnode.c

@@ -822,7 +822,7 @@ v4l2_async_notifier_fwnode_parse_endpoint(struct device *dev,
 	if (ret < 0)
 		goto out_err;
 
-	ret = v4l2_async_notifier_add_subdev(notifier, asd);
+	ret = __v4l2_async_notifier_add_subdev(notifier, asd);
 	if (ret < 0) {
 		/* not an error if asd already exists */
 		if (ret == -EEXIST)

include/media/v4l2-async.h

@@ -133,17 +133,22 @@ void v4l2_async_debug_init(struct dentry *debugfs_dir);
 void v4l2_async_notifier_init(struct v4l2_async_notifier *notifier);
 
 /**
- * v4l2_async_notifier_add_subdev - Add an async subdev to the
+ * __v4l2_async_notifier_add_subdev - Add an async subdev to the
  *				notifier's master asd list.
  *
  * @notifier: pointer to &struct v4l2_async_notifier
  * @asd: pointer to &struct v4l2_async_subdev
  *
+ * \warning: Drivers should avoid using this function and instead use one of:
+ * @v4l2_async_notifier_add_fwnode_subdev,
+ * @v4l2_async_notifier_add_fwnode_remote_subdev or
+ * @v4l2_async_notifier_add_i2c_subdev.
+ *
  * Call this function before registering a notifier to link the provided @asd to
  * the notifiers master @asd_list. The @asd must be allocated with k*alloc() as
  * it will be freed by the framework when the notifier is destroyed.
  */
-int v4l2_async_notifier_add_subdev(struct v4l2_async_notifier *notifier,
+int __v4l2_async_notifier_add_subdev(struct v4l2_async_notifier *notifier,
 				   struct v4l2_async_subdev *asd);
 
 /**