media: mc: entity: Add entity iterator for media_pipeline

Add a media_pipeline_for_each_entity() macro to iterate over entities in
a pipeline. This should be used by driver as a replacement of the
media_graph_walk API, as iterating over the media_pipeline uses the
cached list of pads and is thus more efficient.

Deprecate the media_graph_walk API to indicate it shouldn't be used in
new drivers.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/mc/mc-entity.c

@@ -963,6 +963,43 @@ __media_pipeline_pad_iter_next(struct media_pipeline *pipe,
 }
 EXPORT_SYMBOL_GPL(__media_pipeline_pad_iter_next);
 
+int media_pipeline_entity_iter_init(struct media_pipeline *pipe,
+				    struct media_pipeline_entity_iter *iter)
+{
+	return media_entity_enum_init(&iter->ent_enum, pipe->mdev);
+}
+EXPORT_SYMBOL_GPL(media_pipeline_entity_iter_init);
+
+void media_pipeline_entity_iter_cleanup(struct media_pipeline_entity_iter *iter)
+{
+	media_entity_enum_cleanup(&iter->ent_enum);
+}
+EXPORT_SYMBOL_GPL(media_pipeline_entity_iter_cleanup);
+
+struct media_entity *
+__media_pipeline_entity_iter_next(struct media_pipeline *pipe,
+				  struct media_pipeline_entity_iter *iter,
+				  struct media_entity *entity)
+{
+	if (!entity)
+		iter->cursor = pipe->pads.next;
+
+	while (iter->cursor != &pipe->pads) {
+		struct media_pipeline_pad *ppad;
+		struct media_entity *entity;
+
+		ppad = list_entry(iter->cursor, struct media_pipeline_pad, list);
+		entity = ppad->pad->entity;
+		iter->cursor = iter->cursor->next;
+
+		if (!media_entity_enum_test_and_set(&iter->ent_enum, entity))
+			return entity;
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(__media_pipeline_entity_iter_next);
+
 /* -----------------------------------------------------------------------------
  * Links management
  */

include/media/media-entity.h

@@ -139,6 +139,17 @@ struct media_pipeline_pad_iter {
 	struct list_head *cursor;
 };
 
+/**
+ * struct media_pipeline_entity_iter - Iterator for media_pipeline_for_each_entity
+ *
+ * @ent_enum: The entity enumeration tracker
+ * @cursor: The current element
+ */
+struct media_pipeline_entity_iter {
+	struct media_entity_enum ent_enum;
+	struct list_head *cursor;
+};
+
 /**
  * struct media_link - A link object part of a media graph.
  *
@@ -1077,6 +1088,8 @@ int media_entity_get_fwnode_pad(struct media_entity *entity,
  * @graph: Media graph structure that will be used to walk the graph
  * @mdev: Pointer to the &media_device that contains the object
  *
+ * This function is deprecated, use media_pipeline_for_each_pad() instead.
+ *
  * The caller is required to hold the media_device graph_mutex during the graph
  * walk until the graph state is released.
  *
@@ -1089,6 +1102,8 @@ __must_check int media_graph_walk_init(
  * media_graph_walk_cleanup - Release resources used by graph walk.
  *
  * @graph: Media graph structure that will be used to walk the graph
+ *
+ * This function is deprecated, use media_pipeline_for_each_pad() instead.
  */
 void media_graph_walk_cleanup(struct media_graph *graph);
 
@@ -1099,6 +1114,8 @@ void media_graph_walk_cleanup(struct media_graph *graph);
  * @graph: Media graph structure that will be used to walk the graph
  * @entity: Starting entity
  *
+ * This function is deprecated, use media_pipeline_for_each_pad() instead.
+ *
  * Before using this function, media_graph_walk_init() must be
  * used to allocate resources used for walking the graph. This
  * function initializes the graph traversal structure to walk the
@@ -1114,6 +1131,8 @@ void media_graph_walk_start(struct media_graph *graph,
  * media_graph_walk_next - Get the next entity in the graph
  * @graph: Media graph structure
  *
+ * This function is deprecated, use media_pipeline_for_each_pad() instead.
+ *
  * Perform a depth-first traversal of the given media entities graph.
  *
  * The graph structure must have been previously initialized with a call to
@@ -1194,6 +1213,56 @@ __media_pipeline_pad_iter_next(struct media_pipeline *pipe,
 	     pad != NULL;						\
 	     pad = __media_pipeline_pad_iter_next((pipe), iter, pad))
 
+/**
+ * media_pipeline_entity_iter_init - Initialize a pipeline entity iterator
+ * @pipe: The pipeline
+ * @iter: The iterator
+ *
+ * This function must be called to initialize the iterator before using it in a
+ * media_pipeline_for_each_entity() loop. The iterator must be destroyed by a
+ * call to media_pipeline_entity_iter_cleanup after the loop (including in code
+ * paths that break from the loop).
+ *
+ * The same iterator can be used in multiple consecutive loops without being
+ * destroyed and reinitialized.
+ *
+ * Return: 0 on success or a negative error code otherwise.
+ */
+int media_pipeline_entity_iter_init(struct media_pipeline *pipe,
+				    struct media_pipeline_entity_iter *iter);
+
+/**
+ * media_pipeline_entity_iter_cleanup - Destroy a pipeline entity iterator
+ * @iter: The iterator
+ *
+ * This function must be called to destroy iterators initialized with
+ * media_pipeline_entity_iter_init().
+ */
+void media_pipeline_entity_iter_cleanup(struct media_pipeline_entity_iter *iter);
+
+struct media_entity *
+__media_pipeline_entity_iter_next(struct media_pipeline *pipe,
+				  struct media_pipeline_entity_iter *iter,
+				  struct media_entity *entity);
+
+/**
+ * media_pipeline_for_each_entity - Iterate on all entities in a media pipeline
+ * @pipe: The pipeline
+ * @iter: The iterator (struct media_pipeline_entity_iter)
+ * @entity: The iterator entity
+ *
+ * Iterate on all entities in a media pipeline. This is only valid after the
+ * pipeline has been built with media_pipeline_start() and before it gets
+ * destroyed with media_pipeline_stop(). The iterator must be initialized with
+ * media_pipeline_entity_iter_init() before iteration, and destroyed with
+ * media_pipeline_entity_iter_cleanup() after (including in code paths that
+ * break from the loop).
+ */
+#define media_pipeline_for_each_entity(pipe, iter, entity)			\
+	for (entity = __media_pipeline_entity_iter_next((pipe), iter, NULL);	\
+	     entity != NULL;							\
+	     entity = __media_pipeline_entity_iter_next((pipe), iter, entity))
+
 /**
  * media_pipeline_alloc_start - Mark a pipeline as streaming
  * @pad: Starting pad