[media] media: Amend media graph walk API by init and cleanup functions

Add media_entity_graph_walk_init() and media_entity_graph_walk_cleanup()
functions in order to dynamically allocate memory for the graph. This is
not done in media_entity_graph_walk_start() as there are situations where
e.g. correct error handling, that itself may not fail, requires successful
graph walk.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

1 files changed, 12 insertions, 5 deletions

diff --git a/include/media/media-entity.h b/include/media/media-entity.h
index 4dc3bef72c9d..7f028ea84911 100644
--- a/include/media/media-entity.h
+++ b/include/media/media-entity.h
@@ -699,6 +699,10 @@ struct media_pad *media_entity_remote_pad(struct media_pad *pad);
  */
 struct media_entity *media_entity_get(struct media_entity *entity);
 
+__must_check int media_entity_graph_walk_init(
+        struct media_entity_graph *graph, struct media_device *mdev);
+void media_entity_graph_walk_cleanup(struct media_entity_graph *graph);
+
 /**
  * media_entity_put - Release the reference to the parent module
  *
@@ -715,13 +719,16 @@ void media_entity_put(struct media_entity *entity);
  * @graph: Media graph structure that will be used to walk the graph
  * @entity: Starting entity
  *
- * This function initializes the graph traversal structure to walk the entities
- * graph starting at the given entity. The traversal structure must not be
- * modified by the caller during graph traversal. When done the structure can
- * safely be freed.
+ * Before using this function, media_entity_graph_walk_init() must be
+ * used to allocate resources used for walking the graph. This
+ * function initializes the graph traversal structure to walk the
+ * entities graph starting at the given entity. The traversal
+ * structure must not be modified by the caller during graph
+ * traversal. After the graph walk, the resources must be released
+ * using media_entity_graph_walk_cleanup().
  */
 void media_entity_graph_walk_start(struct media_entity_graph *graph,
-                struct media_entity *entity);
+                                   struct media_entity *entity);
 
 /**
  * media_entity_graph_walk_next - Get the next entity in the graph