[PATCH v6 15/39] [media] v4l2-mc: add a function to inherit controls from a pipeline

[Steve Longerbeam <slongerbeam@gmail.com>]

v4l2_pipeline_inherit_controls() will add the v4l2 controls from
all subdev entities in a pipeline to a given video device.

Signed-off-by: Steve Longerbeam <steve_longerbeam@mentor.com>
---
 drivers/media/v4l2-core/v4l2-mc.c | 50 +++++++++++++++++++++++++++++++++++++++
 include/media/v4l2-mc.h           | 31 ++++++++++++++++++++++++
 2 files changed, 81 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-mc.c b/drivers/media/v4l2-core/v4l2-mc.c
index 303980b..fda580e 100644
--- a/drivers/media/v4l2-core/v4l2-mc.c
+++ b/drivers/media/v4l2-core/v4l2-mc.c
@@ -22,6 +22,7 @@
 #include <linux/usb.h>
 #include <media/media-device.h>
 #include <media/media-entity.h>
+#include <media/v4l2-ctrls.h>
 #include <media/v4l2-fh.h>
 #include <media/v4l2-mc.h>
 #include <media/v4l2-subdev.h>
@@ -238,6 +239,55 @@ int v4l_vb2q_enable_media_source(struct vb2_queue *q)
 }
 EXPORT_SYMBOL_GPL(v4l_vb2q_enable_media_source);
 
+int __v4l2_pipeline_inherit_controls(struct video_device *vfd,
+				     struct media_entity *start_entity)
+{
+	struct media_device *mdev = start_entity->graph_obj.mdev;
+	struct media_entity *entity;
+	struct media_graph graph;
+	struct v4l2_subdev *sd;
+	int ret;
+
+	lockdep_assert_held(&mdev->graph_mutex);
+
+	ret = media_graph_walk_init(&graph, mdev);
+	if (ret)
+		return ret;
+
+	media_graph_walk_start(&graph, start_entity);
+
+	while ((entity = media_graph_walk_next(&graph))) {
+		if (!is_media_entity_v4l2_subdev(entity))
+			continue;
+
+		sd = media_entity_to_v4l2_subdev(entity);
+
+		ret = v4l2_ctrl_add_handler(vfd->ctrl_handler,
+					    sd->ctrl_handler,
+					    NULL);
+		if (ret)
+			break;
+	}
+
+	media_graph_walk_cleanup(&graph);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__v4l2_pipeline_inherit_controls);
+
+int v4l2_pipeline_inherit_controls(struct video_device *vfd,
+				   struct media_entity *start_entity)
+{
+	struct media_device *mdev = start_entity->graph_obj.mdev;
+	int ret;
+
+	mutex_lock(&mdev->graph_mutex);
+	ret = __v4l2_pipeline_inherit_controls(vfd, start_entity);
+	mutex_unlock(&mdev->graph_mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(v4l2_pipeline_inherit_controls);
+
 /* -----------------------------------------------------------------------------
  * Pipeline power management
  *
diff --git a/include/media/v4l2-mc.h b/include/media/v4l2-mc.h
index 2634d9d..299d75d 100644
--- a/include/media/v4l2-mc.h
+++ b/include/media/v4l2-mc.h
@@ -171,6 +171,23 @@ void v4l_disable_media_source(struct video_device *vdev);
  */
 int v4l_vb2q_enable_media_source(struct vb2_queue *q);
 
+/**
+ * v4l2_pipeline_inherit_controls - Add the v4l2 controls from all
+ *				    subdev entities in a pipeline to
+ *				    the given video device.
+ * @vfd: the video device
+ * @start_entity: Starting entity
+ *
+ * This function is intended to be called from the link_notify callback,
+ * which holds the media graph mutex lock. __v4l2_pipeline_inherit_controls
+ * is provided (which does not acquire the lock) for this purpose.
+ * v4l2_pipeline_inherit_controls is also provided for use in other
+ * locations where the graph mutex is not held.
+ */
+int __v4l2_pipeline_inherit_controls(struct video_device *vfd,
+				     struct media_entity *start_entity);
+int v4l2_pipeline_inherit_controls(struct video_device *vfd,
+				   struct media_entity *start_entity);
 
 /**
  * v4l2_pipeline_pm_use - Update the use count of an entity
@@ -231,6 +248,20 @@ static inline int v4l_vb2q_enable_media_source(struct vb2_queue *q)
 	return 0;
 }
 
+static inline int __v4l2_pipeline_inherit_controls(
+	struct video_device *vfd,
+	struct media_entity *start_entity)
+{
+	return 0;
+}
+
+static inline int v4l2_pipeline_inherit_controls(
+	struct video_device *vfd,
+	struct media_entity *start_entity)
+{
+	return 0;
+}
+
 static inline int v4l2_pipeline_pm_use(struct media_entity *entity, int use)
 {
 	return 0;
-- 
2.7.4