media: add helpers for memory-to-memory media controller

A memory-to-memory pipeline device consists in three
entities: two DMA engine and one video processing entities.
The DMA engine entities are linked to a V4L interface.

This commit add a new v4l2_m2m_{un}register_media_controller
API to register this topology.

For instance, a typical mem2mem device topology would
look like this:

Device topology
- entity 1: source (1 pad, 1 link)
            type Node subtype V4L flags 0
	pad0: Source
		-> "proc":1 [ENABLED,IMMUTABLE]

- entity 3: proc (2 pads, 2 links)
            type Node subtype Unknown flags 0
	pad0: Source
		-> "sink":0 [ENABLED,IMMUTABLE]
	pad1: Sink
		<- "source":0 [ENABLED,IMMUTABLE]

- entity 6: sink (1 pad, 1 link)
            type Node subtype V4L flags 0
	pad0: Sink
		<- "proc":0 [ENABLED,IMMUTABLE]

[hans.verkuil@cisco.com: mark interface links as IMMUTABLE]

Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/include/media/v4l2-mem2mem.h b/include/media/v4l2-mem2mem.h
index 8f4b208cfee7..af48b1eca025 100644
--- a/include/media/v4l2-mem2mem.h
+++ b/include/media/v4l2-mem2mem.h
@@ -47,6 +47,7 @@ struct v4l2_m2m_ops {
 	void (*job_abort)(void *priv);
 };
 
+struct video_device;
 struct v4l2_m2m_dev;
 
 /**
@@ -322,6 +323,24 @@ int v4l2_m2m_mmap(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
  */
 struct v4l2_m2m_dev *v4l2_m2m_init(const struct v4l2_m2m_ops *m2m_ops);
 
+#if defined(CONFIG_MEDIA_CONTROLLER)
+void v4l2_m2m_unregister_media_controller(struct v4l2_m2m_dev *m2m_dev);
+int v4l2_m2m_register_media_controller(struct v4l2_m2m_dev *m2m_dev,
+			struct video_device *vdev, int function);
+#else
+static inline void
+v4l2_m2m_unregister_media_controller(struct v4l2_m2m_dev *m2m_dev)
+{
+}
+
+static inline int
+v4l2_m2m_register_media_controller(struct v4l2_m2m_dev *m2m_dev,
+		struct video_device *vdev, int function)
+{
+	return 0;
+}
+#endif
+
 /**
  * v4l2_m2m_release() - cleans up and frees a m2m_dev structure
  *