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[media] v4l: Make video_device inherit from media_entity

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V4L2 devices are media entities. As such they need to inherit from
(include) the media_entity structure.

When registering/unregistering the device, the media entity is
automatically registered/unregistered. The entity is acquired on device
open and released on device close.

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>
This commit is contained in:
Laurent Pinchart
2009-12-09 08:40:10 -03:00
committed by Mauro Carvalho Chehab
parent 95db3a60e0
commit 2c0ab67be1
3 changed files with 87 additions and 7 deletions
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38
Documentation/video4linux/v4l2-framework.txt
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@@ -71,6 +71,10 @@ sub-device instances, the video_device struct stores V4L2 device node data
and in the future a v4l2_fh struct will keep track of filehandle instances
(this is not yet implemented).
The V4L2 framework also optionally integrates with the media framework. If a
driver sets the struct v4l2_device mdev field, sub-devices and video nodes
will automatically appear in the media framework as entities.
struct v4l2_device
------------------
@@ -84,11 +88,14 @@ You must register the device instance:
v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev);
Registration will initialize the v4l2_device struct. If the dev->driver_data
field is NULL, it will be linked to v4l2_dev. Drivers that use the media
device framework in addition to the V4L2 framework need to set
field is NULL, it will be linked to v4l2_dev.
Drivers that want integration with the media device framework need to set
dev->driver_data manually to point to the driver-specific device structure
that embed the struct v4l2_device instance. This is achieved by a
dev_set_drvdata() call before registering the V4L2 device instance.
dev_set_drvdata() call before registering the V4L2 device instance. They must
also set the struct v4l2_device mdev field to point to a properly initialized
and registered media_device instance.
If v4l2_dev->name is empty then it will be set to a value derived from dev
(driver name followed by the bus_id, to be precise). If you set it up before
@@ -530,6 +537,21 @@ If you use v4l2_ioctl_ops, then you should set either .unlocked_ioctl or
The v4l2_file_operations struct is a subset of file_operations. The main
difference is that the inode argument is omitted since it is never used.
If integration with the media framework is needed, you must initialize the
media_entity struct embedded in the video_device struct (entity field) by
calling media_entity_init():
struct media_pad *pad = &my_vdev->pad;
int err;
err = media_entity_init(&vdev->entity, 1, pad, 0);
The pads array must have been previously initialized. There is no need to
manually set the struct media_entity type and name fields.
A reference to the entity will be automatically acquired/released when the
video device is opened/closed.
v4l2_file_operations and locking
--------------------------------
@@ -559,6 +581,9 @@ for you.
return err;
}
If the v4l2_device parent device has a non-NULL mdev field, the video device
entity will be automatically registered with the media device.
Which device is registered depends on the type argument. The following
types exist:
@@ -634,6 +659,13 @@ release, of course) will return an error as well.
When the last user of the video device node exits, then the vdev->release()
callback is called and you can do the final cleanup there.
Don't forget to cleanup the media entity associated with the video device if
it has been initialized:
media_entity_cleanup(&vdev->entity);
This can be done from the release callback.
video_device helper functions
-----------------------------