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

On 09/11/2013 01:33 PM, Laurent Pinchart wrote:

Hi Philipp,

On Wednesday 04 September 2013 16:21:38 Philipp Zabel wrote:

quoted

Am Samstag, den 10.08.2013, 01:03 +0200 schrieb Laurent Pinchart:

quoted

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
[off-list ref]
---

 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

[...]

quoted

@@ -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.

Why? Sorry, I don't see why an encoder is different in this respect than a panel.
I'm sure I'm missing something here.

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.

I think the way this is done today in complex devices is that the driver just
exposes itself as a single sub-device, but internally it has its own pipeline of
sub-devices. The only one that I know of (platform/s5p-tv/hdmi_drv) doesn't expose
them to a media controller, they are completely hidden inside the hdmi driver.

The ability to support hierarchies of entities would be very nice. However, I
don't know how much work that would be to implement and if it is worth the
effort.

Regards,

	Hans

quoted

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.

quoted

		port@0 {
			lvds0_input: endpoint {
			};
		};
		port@1 {
			lvds0_output: endpoint {
			};
		};
	};
	channel@1 {
		port@0 {
			lvds1_input: endpoint {
			};
		};
		lvds1: port@1 {
			lvds1_output: endpoint {
			};
		};
	};
};

quoted

+	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];