Re: [PATCH/RFC v3 06/19] video: display: OF support

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Philipp,

On Wednesday 04 September 2013 16:21:38 Philipp Zabel wrote:
> Am Samstag, den 10.08.2013, 01:03 +0200 schrieb Laurent Pinchart:
> > Extend the notifier with DT node matching support, and add helper
> > functions to build the notifier and link entities based on a graph
> > representation in DT.
> > 
> > Signed-off-by: Laurent Pinchart
> > <laurent.pinchart+renesas@ideasonboard.com>
> > ---
> > 
> >  drivers/video/display/display-core.c     | 334 ++++++++++++++++++++++++++
> >  drivers/video/display/display-notifier.c | 187 +++++++++++++++++
> >  include/video/display.h                  |  45 +++++
> >  3 files changed, 566 insertions(+)
> > 
> > diff --git a/drivers/video/display/display-core.c
> > b/drivers/video/display/display-core.c index c3b47d3..328ead7 100644
> > --- a/drivers/video/display/display-core.c
> > +++ b/drivers/video/display/display-core.c
> 
> [...]
> 
> > @@ -420,6 +599,161 @@ int display_entity_link_graph(struct device *dev,
> > struct list_head *entities)> 
> >  }
> >  EXPORT_SYMBOL_GPL(display_entity_link_graph);
> > 
> > +#ifdef CONFIG_OF
> > +
> > +static int display_of_entity_link_entity(struct device *dev,
> > +					 struct display_entity *entity,
> > +					 struct list_head *entities,
> > +					 struct display_entity *root)
> > +{
> > +	u32 link_flags = MEDIA_LNK_FL_IMMUTABLE | MEDIA_LNK_FL_ENABLED;
> > +	const struct device_node *node = entity->dev->of_node;
> 
> the current device tree matching implementation only allows one display
> entity per linux device. How about adding an of_node pointer to struct
> display_entity directly and allow multiple display entity nodes below in a
> single device node in the device tree?

That's a very good point. We had a similar issues in V4L2, with sensors that 
would create several entities. However, in those cases, the sensors would be 
connected to the rest of the pipeline through a single entity :

Sensor Entity 1 -> ... -> Sensor Entity N -> V4L2 pipeline ...

The core code thus had to care about a single sensor entity when building the 
pipeline. We could solve the problem in a similar way for panels, but encoders 
need a more elaborate solution.

I see (at least) two possibilities here, either explicitly describing all 
entities that make the device in DT (as you have proposed below), or creating 
a hierarchy of entities, with parent entities that can contain several child 
entities. I've CC'ed Guennadi, Hans, Sylwester and Sakari to get their opinion 
on the matter.

> lvds-encoder {
> 	channel@0 {

If I understand this correctly, your LVDS encoder has two independent 
channels. In the general case a device made of multiple entities might have 
those entities chained, so "channel" might not be the best term. "entity" 
might be a better choice.

> 		port@0 {
> 			lvds0_input: endpoint {
> 			};
> 		};
> 		port@1 {
> 			lvds0_output: endpoint {
> 			};
> 		};
> 	};
> 	channel@1 {
> 		port@0 {
> 			lvds1_input: endpoint {
> 			};
> 		};
> 		lvds1: port@1 {
> 			lvds1_output: endpoint {
> 			};
> 		};
> 	};
> };
> 
> > +	struct media_entity *local = &entity->entity;
> > +	struct device_node *ep = NULL;
> > +	int ret = 0;
> > +
> > +	dev_dbg(dev, "creating links for entity %s\n", local->name);
> > +
> > +	while (1) {
> > +		struct media_entity *remote = NULL;
> > +		struct media_pad *remote_pad;
> > +		struct media_pad *local_pad;
> > +		struct display_of_link link;
> > +		struct display_entity *ent;
> > +		struct device_node *next;
> > +
> > +		/* Get the next endpoint and parse its link. */
> > +		next = display_of_get_next_endpoint(node, ep);
> > +		if (next = NULL)
> > +			break;
> > +
> > +		of_node_put(ep);
> > +		ep = next;
> > +
> > +		dev_dbg(dev, "processing endpoint %s\n", ep->full_name);
> > +
> > +		ret = display_of_parse_link(ep, &link);
> > +		if (ret < 0) {
> > +			dev_err(dev, "failed to parse link for %s\n",
> > +				ep->full_name);
> > +			continue;
> > +		}
> > +
> > +		/* Skip source pads, they will be processed from the other end of
> > +		 * the link.
> > +		 */
> > +		if (link.local_port >= local->num_pads) {
> > +			dev_err(dev, "invalid port number %u on %s\n",
> > +				link.local_port, link.local_node->full_name);
> > +			display_of_put_link(&link);
> > +			ret = -EINVAL;
> > +			break;
> > +		}
> > +
> > +		local_pad = &local->pads[link.local_port];
> > +
> > +		if (local_pad->flags & MEDIA_PAD_FL_SOURCE) {
> > +			dev_dbg(dev, "skipping source port %s:%u\n",
> > +				link.local_node->full_name, link.local_port);
> > +			display_of_put_link(&link);
> > +			continue;
> > +		}
> > +
> > +		/* Find the remote entity. If not found, just skip the link as
> > +		 * it goes out of scope of the entities handled by the notifier.
> > +		 */
> > +		list_for_each_entry(ent, entities, list) {
> > +			if (ent->dev->of_node = link.remote_node) {
> > +				remote = &ent->entity;
> > +				break;
> > +			}
> > +		}
> > +
> > +		if (root->dev->of_node = link.remote_node)
> > +			remote = &root->entity;
> > +
> > +		if (remote = NULL) {
> > +			dev_dbg(dev, "no entity found for %s\n",
> > +				link.remote_node->full_name);
> > +			display_of_put_link(&link);
> > +			continue;
> > +		}
> > +
> > +		if (link.remote_port >= remote->num_pads) {
> > +			dev_err(dev, "invalid port number %u on %s\n",
> > +				link.remote_port, link.remote_node->full_name);
> > +			display_of_put_link(&link);
> > +			ret = -EINVAL;
> > +			break;
> > +		}
> > +
> > +		remote_pad = &remote->pads[link.remote_port];
> > +
> > +		display_of_put_link(&link);
> > +
> > +		/* Create the media link. */
> > +		dev_dbg(dev, "creating %s:%u -> %s:%u link\n",
> > +			remote->name, remote_pad->index,
> > +			local->name, local_pad->index);
> > +
> > +		ret = media_entity_create_link(remote, remote_pad->index,
> > +					       local, local_pad->index,
> > +					       link_flags);
> > +		if (ret < 0) {
> > +			dev_err(dev,
> > +				"failed to create %s:%u -> %s:%u link\n",
> > +				remote->name, remote_pad->index,
> > +				local->name, local_pad->index);
> > +			break;
> > +		}
> > +	}
> > +
> > +	of_node_put(ep);
> > +	return ret;
> > +}
> 
> [...]
> 
> For example like this:
> 
> diff --git a/drivers/video/display/display-core.c
> b/drivers/video/display/display-core.c index 7910c23..a04feed 100644
> --- a/drivers/video/display/display-core.c
> +++ b/drivers/video/display/display-core.c
> @@ -302,6 +302,9 @@ int display_entity_init(struct display_entity *entity,
> unsigned int num_sinks, kref_init(&entity->ref);
>  	entity->state = DISPLAY_ENTITY_STATE_OFF;
> 
> +	if (!entity->of_node && entity->dev)
> +		entity->of_node = entity->dev->of_node;
> +
>  	num_pads = num_sinks + num_sources;
>  	pads = kzalloc(sizeof(*pads) * num_pads, GFP_KERNEL);
>  	if (pads = NULL)
> @@ -665,7 +668,7 @@ static int display_of_entity_link_entity(struct device
> *dev, struct display_entity *root)
>  {
>  	u32 link_flags = MEDIA_LNK_FL_IMMUTABLE | MEDIA_LNK_FL_ENABLED;
> -	const struct device_node *node = entity->dev->of_node;
> +	const struct device_node *node = entity->of_node;
>  	struct media_entity *local = &entity->entity;
>  	struct device_node *ep = NULL;
>  	int num_sink, ret = 0;
> @@ -727,13 +730,13 @@ static int display_of_entity_link_entity(struct device
> *dev, * it goes out of scope of the entities handled by the notifier. */
>  		list_for_each_entry(ent, entities, list) {
> -			if (ent->dev->of_node = link.remote_node) {
> +			if (ent->of_node = link.remote_node) {
>  				remote = &ent->entity;
>  				break;
>  			}
>  		}
> 
> -		if (root && root->dev->of_node = link.remote_node)
> +		if (root && root->of_node = link.remote_node)
>  			remote = &root->entity;
> 
>  		if (remote = NULL) {
> diff --git a/drivers/video/display/display-notifier.c
> b/drivers/video/display/display-notifier.c index a3998c7..d0da6e5 100644
> --- a/drivers/video/display/display-notifier.c
> +++ b/drivers/video/display/display-notifier.c
> @@ -28,28 +28,30 @@ static DEFINE_MUTEX(display_entity_mutex);
>   * Notifiers
>   */
> 
> -static bool match_platform(struct device *dev,
> +static bool match_platform(struct display_entity *entity,
>  			   struct display_entity_match *match)
>  {
>  	pr_debug("%s: matching device '%s' with name '%s'\n", __func__,
> -		 dev_name(dev), match->match.platform.name);
> +		 dev_name(entity->dev), match->match.platform.name);
> 
> -	return !strcmp(match->match.platform.name, dev_name(dev));
> +	return !strcmp(match->match.platform.name, dev_name(entity->dev));
>  }
> 
> -static bool match_dt(struct device *dev, struct display_entity_match
> *match) +static bool match_dt(struct display_entity *entity,
> +		     struct display_entity_match *match)
>  {
>  	pr_debug("%s: matching device node '%s' with node '%s'\n", __func__,
> -		 dev->of_node->full_name, match->match.dt.node->full_name);
> +		 entity->of_node->full_name, match->match.dt.node->full_name);
> 
> -	return match->match.dt.node = dev->of_node;
> +	return match->match.dt.node = entity->of_node;
>  }
> 
>  static struct display_entity_match *
>  display_entity_notifier_match(struct display_entity_notifier *notifier,
>  			      struct display_entity *entity)
>  {
> -	bool (*match_func)(struct device *, struct display_entity_match *);
> +	bool (*match_func)(struct display_entity *,
> +			   struct display_entity_match *);
>  	struct display_entity_match *match;
> 
>  	pr_debug("%s: matching entity '%s' (ptr 0x%p dev '%s')\n", __func__,
> @@ -66,7 +68,7 @@ display_entity_notifier_match(struct
> display_entity_notifier *notifier, break;
>  		}
> 
> -		if (match_func(entity->dev, match))
> +		if (match_func(entity, match))
>  			return match;
>  	}
> 
> diff --git a/include/video/display.h b/include/video/display.h
> index 4c402bee..d1f8833 100644
> --- a/include/video/display.h
> +++ b/include/video/display.h
> @@ -228,6 +228,7 @@ struct display_entity {
>  	struct list_head list;
>  	struct device *dev;
>  	struct module *owner;
> +	struct device_node *of_node;
>  	struct kref ref;
> 
>  	char name[32];
-- 
Regards,

Laurent Pinchart