path: root/drivers/media/media-device.c
diff options
authorLaurent Pinchart <laurent.pinchart@ideasonboard.com>2009-12-09 08:40:00 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2011-03-22 04:53:10 -0300
commit53e269c102fbaf77e7dc526b1606ad4a48e57200 (patch)
treec264a16d8058e5331ac3c0c4792be30da50e7363 /drivers/media/media-device.c
parent176fb0d108f7495ccf9aa127e1342a1a0d87e004 (diff)
[media] media: Entities, pads and links
As video hardware pipelines become increasingly complex and configurable, the current hardware description through v4l2 subdevices reaches its limits. In addition to enumerating and configuring subdevices, video camera drivers need a way to discover and modify at runtime how those subdevices are connected. This is done through new elements called entities, pads and links. An entity is a basic media hardware building block. It can correspond to a large variety of logical blocks such as physical hardware devices (CMOS sensor for instance), logical hardware devices (a building block in a System-on-Chip image processing pipeline), DMA channels or physical connectors. A pad is a connection endpoint through which an entity can interact with other entities. Data (not restricted to video) produced by an entity flows from the entity's output to one or more entity inputs. Pads should not be confused with physical pins at chip boundaries. A link is a point-to-point oriented connection between two pads, either on the same entity or on different entities. Data flows from a source pad to a sink pad. Links are stored in the source entity. To make backwards graph walk faster, a copy of all links is also stored in the sink entity. The copy is known as a backlink and is only used to help graph traversal. The entity API is made of three functions: - media_entity_init() initializes an entity. The caller must provide an array of pads as well as an estimated number of links. The links array is allocated dynamically and will be reallocated if it grows beyond the initial estimate. - media_entity_cleanup() frees resources allocated for an entity. It must be called during the cleanup phase after unregistering the entity and before freeing it. - media_entity_create_link() creates a link between two entities. An entry in the link array of each entity is allocated and stores pointers to source and sink pads. When a media device is unregistered, all its entities are unregistered automatically. The code is based on Hans Verkuil <hverkuil@xs4all.nl> initial work. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi> Acked-by: Hans Verkuil <hverkuil@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'drivers/media/media-device.c')
1 files changed, 56 insertions, 0 deletions
diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
index bcd3985d415a..a36509a1df09 100644
--- a/drivers/media/media-device.c
+++ b/drivers/media/media-device.c
@@ -25,6 +25,7 @@
#include <media/media-device.h>
#include <media/media-devnode.h>
+#include <media/media-entity.h>
static const struct media_file_operations media_device_fops = {
.owner = THIS_MODULE,
@@ -69,6 +70,10 @@ int __must_check media_device_register(struct media_device *mdev)
if (WARN_ON(mdev->dev == NULL || mdev->model[0] == 0))
return -EINVAL;
+ mdev->entity_id = 1;
+ INIT_LIST_HEAD(&mdev->entities);
+ spin_lock_init(&mdev->lock);
/* Register the device node. */
mdev->devnode.fops = &media_device_fops;
mdev->devnode.parent = mdev->dev;
@@ -94,7 +99,58 @@ EXPORT_SYMBOL_GPL(media_device_register);
void media_device_unregister(struct media_device *mdev)
+ struct media_entity *entity;
+ struct media_entity *next;
+ list_for_each_entry_safe(entity, next, &mdev->entities, list)
+ media_device_unregister_entity(entity);
device_remove_file(&mdev->devnode.dev, &dev_attr_model);
+ * media_device_register_entity - Register an entity with a media device
+ * @mdev: The media device
+ * @entity: The entity
+ */
+int __must_check media_device_register_entity(struct media_device *mdev,
+ struct media_entity *entity)
+ /* Warn if we apparently re-register an entity */
+ WARN_ON(entity->parent != NULL);
+ entity->parent = mdev;
+ spin_lock(&mdev->lock);
+ if (entity->id == 0)
+ entity->id = mdev->entity_id++;
+ else
+ mdev->entity_id = max(entity->id + 1, mdev->entity_id);
+ list_add_tail(&entity->list, &mdev->entities);
+ spin_unlock(&mdev->lock);
+ return 0;
+ * media_device_unregister_entity - Unregister an entity
+ * @entity: The entity
+ *
+ * If the entity has never been registered this function will return
+ * immediately.
+ */
+void media_device_unregister_entity(struct media_entity *entity)
+ struct media_device *mdev = entity->parent;
+ if (mdev == NULL)
+ return;
+ spin_lock(&mdev->lock);
+ list_del(&entity->list);
+ spin_unlock(&mdev->lock);
+ entity->parent = NULL;

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