[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, 27 insertions, 0 deletions

diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c
index 83cfde6dcb1c..9bf96c71374e 100644
--- a/drivers/media/media-entity.c
+++ b/drivers/media/media-entity.c
@@ -282,6 +282,33 @@ static struct media_entity *stack_pop(struct media_entity_graph *graph)
 #define link_top(en)    ((en)->stack[(en)->top].link)
 #define stack_top(en)   ((en)->stack[(en)->top].entity)
 
+/**
+ * media_entity_graph_walk_init - Allocate resources for graph walk
+ * @graph: Media graph structure that will be used to walk the graph
+ * @mdev: Media device
+ *
+ * Reserve resources for graph walk in media device's current
+ * state. The memory must be released using
+ * media_entity_graph_walk_free().
+ *
+ * Returns error on failure, zero on success.
+ */
+__must_check int media_entity_graph_walk_init(
+        struct media_entity_graph *graph, struct media_device *mdev)
+{
+        return 0;
+}
+EXPORT_SYMBOL_GPL(media_entity_graph_walk_init);
+
+/**
+ * media_entity_graph_walk_cleanup - Release resources related to graph walking
+ * @graph: Media graph structure that was used to walk the graph
+ */
+void media_entity_graph_walk_cleanup(struct media_entity_graph *graph)
+{
+}
+EXPORT_SYMBOL_GPL(media_entity_graph_walk_cleanup);
+
 void media_entity_graph_walk_start(struct media_entity_graph *graph,
                                    struct media_entity *entity)
 {