media: mc: entity: add alloc variant of pipeline_start

Add new variant of media_pipeline_start(), media_pipeline_alloc_start().

media_pipeline_alloc_start() can be used by drivers that do not need to
extend the media_pipeline. The function will either use the pipeline
already associated with the entity, if such exists, or allocate a new
pipeline.

When media_pipeline_stop() is called and the pipeline's use count drops
to zero, the pipeline is automatically freed.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
index 7f933ff89fd4..945bb867a4c1 100644
--- a/drivers/media/v4l2-core/v4l2-dev.c
+++ b/drivers/media/v4l2-core/v4l2-dev.c
@@ -1143,6 +1143,17 @@ void __video_device_pipeline_stop(struct video_device *vdev)
 }
 EXPORT_SYMBOL_GPL(__video_device_pipeline_stop);
 
+__must_check int video_device_pipeline_alloc_start(struct video_device *vdev)
+{
+	struct media_entity *entity = &vdev->entity;
+
+	if (entity->num_pads != 1)
+		return -ENODEV;
+
+	return media_pipeline_alloc_start(entity);
+}
+EXPORT_SYMBOL_GPL(video_device_pipeline_alloc_start);
+
 struct media_pipeline *video_device_pipeline(struct video_device *vdev)
 {
 	struct media_entity *entity = &vdev->entity;