Re: [PATCH v5 03/24] media: entity: Walk the graph based on pads

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Laurent,

On Sun, Apr 18, 2021 at 08:47:37PM +0300, Laurent Pinchart wrote:
> Hi Tomi,
> 
> Thank you for the patch.
> 
> On Thu, Apr 15, 2021 at 04:04:29PM +0300, Tomi Valkeinen wrote:
> > From: Sakari Ailus <sakari.ailus@linux.intel.com>
> 
> And thank you Sakari too.

Thank you for the review!

> 
> > Instead of iterating over graph entities during the walk, iterate the pads
> > through which the entity was first reached. This is required in order to
> > make the entity pipeline pad-based rather than entity based.
> > 
> > Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> > Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> > Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> > ---
> >  Documentation/driver-api/media/mc-core.rst    |  7 ++-
> >  drivers/media/mc/mc-entity.c                  | 49 +++++++++++--------
> >  drivers/media/platform/exynos4-is/media-dev.c | 20 ++++----
> >  drivers/media/platform/omap3isp/ispvideo.c    | 17 ++++---
> >  drivers/media/platform/vsp1/vsp1_video.c      | 12 ++---
> >  drivers/media/platform/xilinx/xilinx-dma.c    | 12 ++---
> >  drivers/media/v4l2-core/v4l2-mc.c             | 24 ++++-----
> >  drivers/staging/media/omap4iss/iss_video.c    | 34 +++++++------
> >  include/media/media-entity.h                  |  7 +--
> >  9 files changed, 99 insertions(+), 83 deletions(-)
> > 
> > diff --git a/Documentation/driver-api/media/mc-core.rst b/Documentation/driver-api/media/mc-core.rst
> > index ba0aee982124..8a13640bed56 100644
> > --- a/Documentation/driver-api/media/mc-core.rst
> > +++ b/Documentation/driver-api/media/mc-core.rst
> > @@ -169,8 +169,11 @@ Drivers initiate a graph traversal by calling
> >  The graph structure, provided by the caller, is initialized to start graph
> >  traversal at the given pad in an entity.
> >  
> > -Drivers can then retrieve the next entity by calling
> > -:c:func:`media_graph_walk_next()`
> > +Drivers can then retrieve the next pad by calling
> > +:c:func:`media_graph_walk_next()`. Only the pad through which the entity
> > +is first reached is returned. If the caller is interested in knowing which
> > +further pads would be connected, the :c:func:`media_entity_has_route()`
> > +function can be used for that.
> >  
> >  When the graph traversal is complete the function will return ``NULL``.
> >  
> > diff --git a/drivers/media/mc/mc-entity.c b/drivers/media/mc/mc-entity.c
> > index 44a05806b589..401fddf320e7 100644
> > --- a/drivers/media/mc/mc-entity.c
> > +++ b/drivers/media/mc/mc-entity.c
> > @@ -340,9 +340,9 @@ static void media_graph_walk_iter(struct media_graph *graph)
> >  		next->entity->name, next->index);
> >  }
> >  
> > -struct media_entity *media_graph_walk_next(struct media_graph *graph)
> > +struct media_pad *media_graph_walk_next(struct media_graph *graph)
> >  {
> > -	struct media_entity *entity;
> > +	struct media_pad *pad;
> >  
> >  	if (stack_top(graph) == NULL)
> >  		return NULL;
> > @@ -355,11 +355,11 @@ struct media_entity *media_graph_walk_next(struct media_graph *graph)
> >  	while (link_top(graph) != &stack_top(graph)->entity->links)
> >  		media_graph_walk_iter(graph);
> >  
> > -	entity = stack_pop(graph)->entity;
> > -	dev_dbg(entity->graph_obj.mdev->dev,
> > -		"walk: returning entity '%s'\n", entity->name);
> > +	pad = stack_pop(graph);
> > +	dev_dbg(pad->graph_obj.mdev->dev,
> > +		"walk: returning pad '%s':%u\n", pad->entity->name, pad->index);
> >  
> > -	return entity;
> > +	return pad;
> >  }
> >  EXPORT_SYMBOL_GPL(media_graph_walk_next);
> >  
> > @@ -407,7 +407,8 @@ __must_check int __media_pipeline_start(struct media_entity *entity,
> >  {
> >  	struct media_device *mdev = entity->graph_obj.mdev;
> >  	struct media_graph *graph = &pipe->graph;
> > -	struct media_entity *entity_err = entity;
> > +	struct media_pad *pad = entity->pads;
> > +	struct media_pad *pad_err = pad;
> >  	struct media_link *link;
> >  	int ret;
> >  
> > @@ -417,9 +418,11 @@ __must_check int __media_pipeline_start(struct media_entity *entity,
> >  			goto error_graph_walk_start;
> >  	}
> >  
> > -	media_graph_walk_start(&pipe->graph, entity->pads);
> > +	media_graph_walk_start(&pipe->graph, pad);
> > +
> > +	while ((pad = media_graph_walk_next(graph))) {
> > +		struct media_entity *entity = pad->entity;
> >  
> > -	while ((entity = media_graph_walk_next(graph))) {
> >  		DECLARE_BITMAP(active, MEDIA_ENTITY_MAX_PADS);
> >  		DECLARE_BITMAP(has_no_links, MEDIA_ENTITY_MAX_PADS);
> >  
> > @@ -428,7 +431,7 @@ __must_check int __media_pipeline_start(struct media_entity *entity,
> >  		if (entity->pipe && entity->pipe != pipe) {
> >  			pr_err("Pipe active for %s. Can't start for %s\n",
> >  				entity->name,
> > -				entity_err->name);
> > +				pad_err->entity->name);
> >  			ret = -EBUSY;
> >  			goto error;
> >  		}
> > @@ -446,11 +449,12 @@ __must_check int __media_pipeline_start(struct media_entity *entity,
> >  		bitmap_fill(has_no_links, entity->num_pads);
> >  
> >  		list_for_each_entry(link, &entity->links, list) {
> > -			struct media_pad *pad = link->sink->entity == entity
> > -						? link->sink : link->source;
> > +			struct media_pad *other_pad =
> > +				link->sink->entity == entity ?
> > +				link->sink : link->source;
> >  
> >  			/* Mark that a pad is connected by a link. */
> > -			bitmap_clear(has_no_links, pad->index, 1);
> > +			bitmap_clear(has_no_links, other_pad->index, 1);
> >  
> >  			/*
> >  			 * Pads that either do not need to connect or
> > @@ -459,13 +463,13 @@ __must_check int __media_pipeline_start(struct media_entity *entity,
> >  			 */
> >  			if (!(pad->flags & MEDIA_PAD_FL_MUST_CONNECT) ||
> 
> Shouldn't this be other_pad->flags ?

Correct. Nice find!

> 
> >  			    link->flags & MEDIA_LNK_FL_ENABLED)
> > -				bitmap_set(active, pad->index, 1);
> > +				bitmap_set(active, other_pad->index, 1);
> >  
> >  			/*
> >  			 * Link validation will only take place for
> >  			 * sink ends of the link that are enabled.
> >  			 */
> > -			if (link->sink != pad ||
> > +			if (link->sink != other_pad ||
> >  			    !(link->flags & MEDIA_LNK_FL_ENABLED))
> >  				continue;
> >  
> > @@ -501,9 +505,11 @@ __must_check int __media_pipeline_start(struct media_entity *entity,
> >  	 * Link validation on graph failed. We revert what we did and
> >  	 * return the error.
> >  	 */
> > -	media_graph_walk_start(graph, entity_err->pads);
> > +	media_graph_walk_start(graph, pad_err);
> > +
> > +	while ((pad_err = media_graph_walk_next(graph))) {
> > +		struct media_entity *entity_err = pad_err->entity;
> >  
> > -	while ((entity_err = media_graph_walk_next(graph))) {
> >  		/* Sanity check for negative stream_count */
> >  		if (!WARN_ON_ONCE(entity_err->stream_count <= 0)) {
> >  			entity_err->stream_count--;
> > @@ -515,7 +521,7 @@ __must_check int __media_pipeline_start(struct media_entity *entity,
> >  		 * We haven't increased stream_count further than this
> >  		 * so we quit here.
> >  		 */
> > -		if (entity_err == entity)
> > +		if (pad_err == pad)
> >  			break;
> >  	}
> >  
> > @@ -542,8 +548,9 @@ EXPORT_SYMBOL_GPL(media_pipeline_start);
> >  
> >  void __media_pipeline_stop(struct media_entity *entity)
> >  {
> > -	struct media_graph *graph = &entity->pipe->graph;
> >  	struct media_pipeline *pipe = entity->pipe;
> > +	struct media_graph *graph = &pipe->graph;
> > +	struct media_pad *pad;
> >  
> >  	/*
> >  	 * If the following check fails, the driver has performed an
> > @@ -554,7 +561,9 @@ void __media_pipeline_stop(struct media_entity *entity)
> >  
> >  	media_graph_walk_start(graph, entity->pads);
> >  
> > -	while ((entity = media_graph_walk_next(graph))) {
> > +	while ((pad = media_graph_walk_next(graph))) {
> > +		struct media_entity *entity = pad->entity;
> > +
> >  		/* Sanity check for negative stream_count */
> >  		if (!WARN_ON_ONCE(entity->stream_count <= 0)) {
> >  			entity->stream_count--;
> > diff --git a/drivers/media/platform/exynos4-is/media-dev.c b/drivers/media/platform/exynos4-is/media-dev.c
> > index d90663b65932..b910a23b7e23 100644
> > --- a/drivers/media/platform/exynos4-is/media-dev.c
> > +++ b/drivers/media/platform/exynos4-is/media-dev.c
> > @@ -1166,7 +1166,7 @@ static int __fimc_md_modify_pipeline(struct media_entity *entity, bool enable)
> >  static int __fimc_md_modify_pipelines(struct media_entity *entity, bool enable,
> >  				      struct media_graph *graph)
> >  {
> > -	struct media_entity *entity_err = entity;
> > +	struct media_pad *pad, *pad_err = entity->pads;
> >  	int ret;
> >  
> >  	/*
> > @@ -1175,13 +1175,13 @@ static int __fimc_md_modify_pipelines(struct media_entity *entity, bool enable,
> >  	 * through active links. This is needed as we cannot power on/off the
> >  	 * subdevs in random order.
> >  	 */
> > -	media_graph_walk_start(graph, entity->pads);
> > +	media_graph_walk_start(graph, pad_err);
> >  
> > -	while ((entity = media_graph_walk_next(graph))) {
> > -		if (!is_media_entity_v4l2_video_device(entity))
> > +	while ((pad = media_graph_walk_next(graph))) {
> > +		if (!is_media_entity_v4l2_video_device(pad->entity))
> >  			continue;
> >  
> > -		ret  = __fimc_md_modify_pipeline(entity, enable);
> > +		ret  = __fimc_md_modify_pipeline(pad->entity, enable);
> >  
> >  		if (ret < 0)
> >  			goto err;
> > @@ -1190,15 +1190,15 @@ static int __fimc_md_modify_pipelines(struct media_entity *entity, bool enable,
> >  	return 0;
> >  
> >  err:
> > -	media_graph_walk_start(graph, entity_err->pads);
> > +	media_graph_walk_start(graph, pad_err);
> >  
> > -	while ((entity_err = media_graph_walk_next(graph))) {
> > -		if (!is_media_entity_v4l2_video_device(entity_err))
> > +	while ((pad_err = media_graph_walk_next(graph))) {
> > +		if (!is_media_entity_v4l2_video_device(pad_err->entity))
> >  			continue;
> >  
> > -		__fimc_md_modify_pipeline(entity_err, !enable);
> > +		__fimc_md_modify_pipeline(pad_err->entity, !enable);
> >  
> > -		if (entity_err == entity)
> > +		if (pad_err == pad)
> >  			break;
> >  	}
> >  
> > diff --git a/drivers/media/platform/omap3isp/ispvideo.c b/drivers/media/platform/omap3isp/ispvideo.c
> > index 3c1485d59404..49cde04bfb21 100644
> > --- a/drivers/media/platform/omap3isp/ispvideo.c
> > +++ b/drivers/media/platform/omap3isp/ispvideo.c
> > @@ -222,8 +222,8 @@ static int isp_video_get_graph_data(struct isp_video *video,
> >  				    struct isp_pipeline *pipe)
> >  {
> >  	struct media_graph graph;
> > -	struct media_entity *entity = &video->video.entity;
> > -	struct media_device *mdev = entity->graph_obj.mdev;
> > +	struct media_pad *pad = video->video.entity.pads;
> > +	struct media_device *mdev = pad->entity->graph_obj.mdev;
> 
> Maybe video->video.entity.graph_obj.mdev ? Same below.

Could be. That doesn't really matter though.

> 
> >  	struct isp_video *far_end = NULL;
> >  	int ret;
> >  
> > @@ -234,23 +234,24 @@ static int isp_video_get_graph_data(struct isp_video *video,
> >  		return ret;
> >  	}
> >  
> > -	media_graph_walk_start(&graph, entity->pads);
> > +	media_graph_walk_start(&graph, pad);
> >  
> > -	while ((entity = media_graph_walk_next(&graph))) {
> > +	while ((pad = media_graph_walk_next(&graph))) {
> >  		struct isp_video *__video;
> >  
> > -		media_entity_enum_set(&pipe->ent_enum, entity);
> > +		media_entity_enum_set(&pipe->ent_enum, pad->entity);
> >  
> >  		if (far_end != NULL)
> >  			continue;
> >  
> > -		if (entity == &video->video.entity)
> > +		if (pad == video->video.entity.pads)
> >  			continue;
> >  
> > -		if (!is_media_entity_v4l2_video_device(entity))
> > +		if (!is_media_entity_v4l2_video_device(pad->entity))
> >  			continue;
> >  
> > -		__video = to_isp_video(media_entity_to_video_device(entity));
> > +		__video = to_isp_video(media_entity_to_video_device(
> > +					       pad->entity));
> >  		if (__video->type != video->type)
> >  			far_end = __video;
> >  	}
> > diff --git a/drivers/media/platform/vsp1/vsp1_video.c b/drivers/media/platform/vsp1/vsp1_video.c
> > index 61e4fbaba7b7..39dccf347ce1 100644
> > --- a/drivers/media/platform/vsp1/vsp1_video.c
> > +++ b/drivers/media/platform/vsp1/vsp1_video.c
> > @@ -559,8 +559,8 @@ static int vsp1_video_pipeline_build(struct vsp1_pipeline *pipe,
> >  				     struct vsp1_video *video)
> >  {
> >  	struct media_graph graph;
> > -	struct media_entity *entity = &video->video.entity;
> > -	struct media_device *mdev = entity->graph_obj.mdev;
> > +	struct media_pad *pad = video->video.entity.pads;
> > +	struct media_device *mdev = pad->entity->graph_obj.mdev;
> >  	unsigned int i;
> >  	int ret;
> >  
> > @@ -569,17 +569,17 @@ static int vsp1_video_pipeline_build(struct vsp1_pipeline *pipe,
> >  	if (ret)
> >  		return ret;
> >  
> > -	media_graph_walk_start(&graph, entity->pads);
> > +	media_graph_walk_start(&graph, pad);
> >  
> > -	while ((entity = media_graph_walk_next(&graph))) {
> > +	while ((pad = media_graph_walk_next(&graph))) {
> >  		struct v4l2_subdev *subdev;
> >  		struct vsp1_rwpf *rwpf;
> >  		struct vsp1_entity *e;
> >  
> > -		if (!is_media_entity_v4l2_subdev(entity))
> > +		if (!is_media_entity_v4l2_subdev(pad->entity))
> >  			continue;
> >  
> > -		subdev = media_entity_to_v4l2_subdev(entity);
> > +		subdev = media_entity_to_v4l2_subdev(pad->entity);
> >  		e = to_vsp1_entity(subdev);
> >  		list_add_tail(&e->list_pipe, &pipe->entities);
> >  		e->pipe = pipe;
> > diff --git a/drivers/media/platform/xilinx/xilinx-dma.c b/drivers/media/platform/xilinx/xilinx-dma.c
> > index d64c3bee8b95..8df3c43aecbe 100644
> > --- a/drivers/media/platform/xilinx/xilinx-dma.c
> > +++ b/drivers/media/platform/xilinx/xilinx-dma.c
> > @@ -175,8 +175,8 @@ static int xvip_pipeline_validate(struct xvip_pipeline *pipe,
> >  				  struct xvip_dma *start)
> >  {
> >  	struct media_graph graph;
> > -	struct media_entity *entity = &start->video.entity;
> > -	struct media_device *mdev = entity->graph_obj.mdev;
> > +	struct media_pad *pad = start->video.entity.pads;
> > +	struct media_device *mdev = pad->entity->graph_obj.mdev;
> >  	unsigned int num_inputs = 0;
> >  	unsigned int num_outputs = 0;
> >  	int ret;
> > @@ -190,15 +190,15 @@ static int xvip_pipeline_validate(struct xvip_pipeline *pipe,
> >  		return ret;
> >  	}
> >  
> > -	media_graph_walk_start(&graph, entity->pads);
> > +	media_graph_walk_start(&graph, pad);
> >  
> > -	while ((entity = media_graph_walk_next(&graph))) {
> > +	while ((pad = media_graph_walk_next(&graph))) {
> >  		struct xvip_dma *dma;
> >  
> > -		if (entity->function != MEDIA_ENT_F_IO_V4L)
> > +		if (pad->entity->function != MEDIA_ENT_F_IO_V4L)
> >  			continue;
> >  
> > -		dma = to_xvip_dma(media_entity_to_video_device(entity));
> > +		dma = to_xvip_dma(media_entity_to_video_device(pad->entity));
> >  
> >  		if (dma->pad.flags & MEDIA_PAD_FL_SINK) {
> >  			pipe->output = dma;
> > diff --git a/drivers/media/v4l2-core/v4l2-mc.c b/drivers/media/v4l2-core/v4l2-mc.c
> > index d215fe31b9a2..cbeb580c6754 100644
> > --- a/drivers/media/v4l2-core/v4l2-mc.c
> > +++ b/drivers/media/v4l2-core/v4l2-mc.c
> > @@ -434,13 +434,14 @@ EXPORT_SYMBOL_GPL(v4l2_create_fwnode_links);
> >  static int pipeline_pm_use_count(struct media_entity *entity,
> >  	struct media_graph *graph)
> >  {
> > +	struct media_pad *pad;
> >  	int use = 0;
> >  
> >  	media_graph_walk_start(graph, entity->pads);
> >  
> > -	while ((entity = media_graph_walk_next(graph))) {
> > -		if (is_media_entity_v4l2_video_device(entity))
> > -			use += entity->use_count;
> > +	while ((pad = media_graph_walk_next(graph))) {
> > +		if (is_media_entity_v4l2_video_device(pad->entity))
> > +			use += pad->entity->use_count;
> >  	}
> >  
> >  	return use;
> > @@ -493,7 +494,7 @@ static int pipeline_pm_power_one(struct media_entity *entity, int change)
> >  static int pipeline_pm_power(struct media_entity *entity, int change,
> >  	struct media_graph *graph)
> >  {
> > -	struct media_entity *first = entity;
> > +	struct media_pad *tmp_pad, *pad;
> >  	int ret = 0;
> >  
> >  	if (!change)
> > @@ -501,19 +502,18 @@ static int pipeline_pm_power(struct media_entity *entity, int change,
> >  
> >  	media_graph_walk_start(graph, entity->pads);
> >  
> > -	while (!ret && (entity = media_graph_walk_next(graph)))
> > -		if (is_media_entity_v4l2_subdev(entity))
> > -			ret = pipeline_pm_power_one(entity, change);
> > +	while (!ret && (pad = media_graph_walk_next(graph)))
> > +		if (is_media_entity_v4l2_subdev(pad->entity))
> > +			ret = pipeline_pm_power_one(pad->entity, change);
> >  
> >  	if (!ret)
> >  		return ret;
> >  
> > -	media_graph_walk_start(graph, first->pads);
> > +	media_graph_walk_start(graph, entity->pads);
> >  
> > -	while ((first = media_graph_walk_next(graph))
> > -	       && first != entity)
> > -		if (is_media_entity_v4l2_subdev(first))
> > -			pipeline_pm_power_one(first, -change);
> > +	while ((tmp_pad = media_graph_walk_next(graph)) && tmp_pad != pad)
> > +		if (is_media_entity_v4l2_subdev(tmp_pad->entity))
> > +			pipeline_pm_power_one(tmp_pad->entity, -change);
> >  
> >  	return ret;
> >  }
> > diff --git a/drivers/staging/media/omap4iss/iss_video.c b/drivers/staging/media/omap4iss/iss_video.c
> > index 77bf1b8a56f7..9f3ff5a37d90 100644
> > --- a/drivers/staging/media/omap4iss/iss_video.c
> > +++ b/drivers/staging/media/omap4iss/iss_video.c
> > @@ -206,8 +206,8 @@ static struct iss_video *
> >  iss_video_far_end(struct iss_video *video)
> >  {
> >  	struct media_graph graph;
> > -	struct media_entity *entity = &video->video.entity;
> > -	struct media_device *mdev = entity->graph_obj.mdev;
> > +	struct media_pad *pad = video->video.entity.pads;
> > +	struct media_device *mdev = pad->entity->graph_obj.mdev;
> >  	struct iss_video *far_end = NULL;
> >  
> >  	mutex_lock(&mdev->graph_mutex);
> > @@ -217,16 +217,17 @@ iss_video_far_end(struct iss_video *video)
> >  		return NULL;
> >  	}
> >  
> > -	media_graph_walk_start(&graph, entity->pads);
> > +	media_graph_walk_start(&graph, pad);
> >  
> > -	while ((entity = media_graph_walk_next(&graph))) {
> > -		if (entity == &video->video.entity)
> > +	while ((pad = media_graph_walk_next(&graph))) {
> > +		if (pad->entity == &video->video.entity)
> >  			continue;
> >  
> > -		if (!is_media_entity_v4l2_video_device(entity))
> > +		if (!is_media_entity_v4l2_video_device(pad->entity))
> >  			continue;
> >  
> > -		far_end = to_iss_video(media_entity_to_video_device(entity));
> > +		far_end = to_iss_video(media_entity_to_video_device(
> > +						pad->entity));
> >  		if (far_end->type != video->type)
> >  			break;
> >  
> > @@ -853,7 +854,7 @@ iss_video_streamon(struct file *file, void *fh, enum v4l2_buf_type type)
> >  	struct iss_video_fh *vfh = to_iss_video_fh(fh);
> >  	struct iss_video *video = video_drvdata(file);
> >  	struct media_graph graph;
> > -	struct media_entity *entity = &video->video.entity;
> > +	struct media_pad *pad = video->video.entity.pads;
> >  	enum iss_pipeline_state state;
> >  	struct iss_pipeline *pipe;
> >  	struct iss_video *far_end;
> > @@ -869,30 +870,31 @@ iss_video_streamon(struct file *file, void *fh, enum v4l2_buf_type type)
> >  	 * Start streaming on the pipeline. No link touching an entity in the
> >  	 * pipeline can be activated or deactivated once streaming is started.
> >  	 */
> > -	pipe = entity->pipe
> > -	     ? to_iss_pipeline(entity) : &video->pipe;
> > +	pipe = pad->entity->pipe
> > +	     ? to_iss_pipeline(pad->entity) : &video->pipe;
> >  	pipe->external = NULL;
> >  	pipe->external_rate = 0;
> >  	pipe->external_bpp = 0;
> >  
> > -	ret = media_entity_enum_init(&pipe->ent_enum, entity->graph_obj.mdev);
> > +	ret = media_entity_enum_init(&pipe->ent_enum,
> > +				     pad->entity->graph_obj.mdev);
> >  	if (ret)
> >  		goto err_graph_walk_init;
> >  
> > -	ret = media_graph_walk_init(&graph, entity->graph_obj.mdev);
> > +	ret = media_graph_walk_init(&graph, pad->entity->graph_obj.mdev);
> >  	if (ret)
> >  		goto err_graph_walk_init;
> >  
> >  	if (video->iss->pdata->set_constraints)
> >  		video->iss->pdata->set_constraints(video->iss, true);
> >  
> > -	ret = media_pipeline_start(entity, &pipe->pipe);
> > +	ret = media_pipeline_start(pad->entity, &pipe->pipe);
> >  	if (ret < 0)
> >  		goto err_media_pipeline_start;
> >  
> > -	media_graph_walk_start(&graph, entity->pads);
> > -	while ((entity = media_graph_walk_next(&graph)))
> > -		media_entity_enum_set(&pipe->ent_enum, entity);
> > +	media_graph_walk_start(&graph, pad);
> > +	while ((pad = media_graph_walk_next(&graph)))
> > +		media_entity_enum_set(&pipe->ent_enum, pad->entity);
> >  
> >  	/*
> >  	 * Verify that the currently configured format matches the output of
> > diff --git a/include/media/media-entity.h b/include/media/media-entity.h
> > index 97b170cf38eb..2d45344ca527 100644
> > --- a/include/media/media-entity.h
> > +++ b/include/media/media-entity.h
> > @@ -921,10 +921,11 @@ void media_graph_walk_start(struct media_graph *graph, struct media_pad *pad);
> >   * The graph structure must have been previously initialized with a call to
> >   * media_graph_walk_start().
> >   *
> > - * Return: returns the next entity in the graph or %NULL if the whole graph
> > - * have been traversed.
> > + * Return: returns the next pad in the graph or %NULL if the whole
> > + * graph have been traversed. The pad which is returned is the pad
> > + * through which a new entity is reached when parsing the graph.
> 
> "next pad in the graph" is a bit confusing. The next sentence clarifies
> it, but maybe we can do better:
> 
>  * Return: returns the next entity in the graph, identified by the pad through
>  * which it has been reached. If the whole graph has been traversed, return
>  * %NULL.
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Thanks!

> 
> >   */
> > -struct media_entity *media_graph_walk_next(struct media_graph *graph);
> > +struct media_pad *media_graph_walk_next(struct media_graph *graph);
> >  
> >  /**
> >   * media_pipeline_start - Mark a pipeline as streaming
> 

-- 
Regards,

Sakari Ailus