[media] media: Entity graph traversal

Add media entity graph traversal. The traversal follows enabled links by
depth first. Traversing graph backwards is prevented by comparing the next
possible entity in the graph with the previous one. Multiply connected
graphs are thus not supported.

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Vimarsh Zutshi <vimarsh.zutshi@gmail.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/include/media/media-entity.h b/include/media/media-entity.h
index f6c856c9ac16..28f61f6ee549 100644
--- a/include/media/media-entity.h
+++ b/include/media/media-entity.h
@@ -113,10 +113,25 @@ static inline u32 media_entity_subtype(struct media_entity *entity)
         return entity->type & MEDIA_ENT_SUBTYPE_MASK;
 }
 
+#define MEDIA_ENTITY_ENUM_MAX_DEPTH     16
+
+struct media_entity_graph {
+        struct {
+                struct media_entity *entity;
+                int link;
+        } stack[MEDIA_ENTITY_ENUM_MAX_DEPTH];
+        int top;
+};
+
 int media_entity_init(struct media_entity *entity, u16 num_pads,
                 struct media_pad *pads, u16 extra_links);
 void media_entity_cleanup(struct media_entity *entity);
 int media_entity_create_link(struct media_entity *source, u16 source_pad,
                 struct media_entity *sink, u16 sink_pad, u32 flags);
 
+void media_entity_graph_walk_start(struct media_entity_graph *graph,
+                struct media_entity *entity);
+struct media_entity *
+media_entity_graph_walk_next(struct media_entity_graph *graph);
+
 #endif