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>

drivers/media/mc/mc-entity.c

@@ -530,6 +530,8 @@ void __media_pipeline_stop(struct media_entity *entity)
 
 	media_graph_walk_cleanup(graph);
 
+	if (pipe->allocated)
+		kfree(pipe);
 }
 EXPORT_SYMBOL_GPL(__media_pipeline_stop);
 
@@ -543,6 +545,42 @@ void media_pipeline_stop(struct media_entity *entity)
 }
 EXPORT_SYMBOL_GPL(media_pipeline_stop);
 
+__must_check int media_pipeline_alloc_start(struct media_entity *entity)
+{
+	struct media_device *mdev = entity->graph_obj.mdev;
+	struct media_pipeline *new_pipe = NULL;
+	struct media_pipeline *pipe;
+	int ret;
+
+	mutex_lock(&mdev->graph_mutex);
+
+	/*
+	 * Is the entity already part of a pipeline? If not, we need to allocate
+	 * a pipe.
+	 */
+	pipe = media_entity_pipeline(entity);
+	if (!pipe) {
+		new_pipe = kzalloc(sizeof(*new_pipe), GFP_KERNEL);
+		if (!new_pipe) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		pipe = new_pipe;
+		pipe->allocated = true;
+	}
+
+	ret = __media_pipeline_start(entity, pipe);
+	if (ret)
+		kfree(new_pipe);
+
+out:
+	mutex_unlock(&mdev->graph_mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(media_pipeline_alloc_start);
+
 /* -----------------------------------------------------------------------------
  * Links management
  */

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;

include/media/media-entity.h

@@ -100,10 +100,12 @@ struct media_graph {
 /**
  * struct media_pipeline - Media pipeline related information
  *
+ * @allocated:		Media pipeline allocated and freed by the framework
  * @start_count:	Media pipeline start - stop count
  * @graph:		Media graph walk during pipeline start / stop
  */
 struct media_pipeline {
+	bool allocated;
 	int start_count;
 	struct media_graph graph;
 };
@@ -1092,6 +1094,19 @@ void media_pipeline_stop(struct media_entity *entity);
  */
 void __media_pipeline_stop(struct media_entity *entity);
 
+/**
+ * media_pipeline_alloc_start - Mark a pipeline as streaming
+ * @entity: Starting entity
+ *
+ * media_pipeline_alloc_start() is similar to media_pipeline_start() but instead
+ * of working on a given pipeline the function will use an existing pipeline if
+ * the entity is already part of a pipeline, or allocate a new pipeline.
+ *
+ * Calls to media_pipeline_alloc_start() must be matched with
+ * media_pipeline_stop().
+ */
+__must_check int media_pipeline_alloc_start(struct media_entity *entity);
+
 /**
  * media_devnode_create() - creates and initializes a device node interface
  *

include/media/v4l2-dev.h

@@ -607,6 +607,20 @@ void video_device_pipeline_stop(struct video_device *vdev);
  */
 void __video_device_pipeline_stop(struct video_device *vdev);
 
+/**
+ * video_device_pipeline_alloc_start - Mark a pipeline as streaming
+ * @vdev: Starting video device
+ *
+ * video_device_pipeline_alloc_start() is similar to video_device_pipeline_start()
+ * but instead of working on a given pipeline the function will use an
+ * existing pipeline if the video device is already part of a pipeline, or
+ * allocate a new pipeline.
+ *
+ * Calls to video_device_pipeline_alloc_start() must be matched with
+ * video_device_pipeline_stop().
+ */
+__must_check int video_device_pipeline_alloc_start(struct video_device *vdev);
+
 /**
  * video_device_pipeline - Get the media pipeline a video device is part of
  * @vdev: The video device