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@xxxxxxxxxxxxxxxx>
Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxxxxxxxxxxxxx>
---
Documentation/video4linux/v4l2-framework.txt | 38 +++++++++++++++++++++++--
drivers/media/video/v4l2-dev.c | 35 ++++++++++++++++++++++-
include/media/v4l2-dev.h | 6 ++++
3 files changed, 74 insertions(+), 5 deletions(-)
diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt
index 8a3f14e..0d9b8ce 100644
--- a/Documentation/video4linux/v4l2-framework.txt
+++ b/Documentation/video4linux/v4l2-framework.txt
@@ -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
@@ -523,6 +530,21 @@ 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_entity_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, subtype and name fields.
+
+A reference to the entity will be automatically acquired/released when the
+video device is opened/closed.
+
video_device registration
-------------------------
@@ -536,6 +558,9 @@ 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:
@@ -613,6 +638,13 @@ those will still be passed on since some buffer ioctls may still be needed.
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
-----------------------------
diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c
index bcd47a0..e70424c 100644
--- a/drivers/media/video/v4l2-dev.c
+++ b/drivers/media/video/v4l2-dev.c
@@ -269,6 +269,7 @@ static int v4l2_mmap(struct file *filp, struct vm_area_struct *vm)
static int v4l2_open(struct inode *inode, struct file *filp)
{
struct video_device *vdev;
+ struct media_entity *entity = NULL;
int ret = 0;
/* Check if the video device is available */
@@ -283,12 +284,22 @@ static int v4l2_open(struct inode *inode, struct file *filp)
/* and increase the device refcount */
video_get(vdev);
mutex_unlock(&videodev_lock);
+ if (vdev->v4l2_dev && vdev->v4l2_dev->mdev) {
+ entity = media_entity_get(&vdev->entity);
+ if (!entity) {
+ ret = -EBUSY;
+ video_put(vdev);
+ return ret;
+ }
+ }
if (vdev->fops->open)
ret = vdev->fops->open(filp);
/* decrease the refcount in case of an error */
- if (ret)
+ if (ret) {
+ media_entity_put(entity);
video_put(vdev);
+ }
return ret;
}
@@ -301,6 +312,9 @@ static int v4l2_release(struct inode *inode, struct file *filp)
if (vdev->fops->release)
vdev->fops->release(filp);
+ if (vdev->v4l2_dev && vdev->v4l2_dev->mdev)
+ media_entity_put(&vdev->entity);
+
/* decrease the refcount unconditionally since the release()
return value is ignored. */
video_put(vdev);
@@ -563,11 +577,25 @@ int __video_register_device(struct video_device *vdev, int type, int nr,
printk(KERN_WARNING "%s: requested %s%d, got %s\n", __func__,
name_base, nr, video_device_node_name(vdev));
- /* Part 5: Activate this minor. The char device can now be used. */
+ /* Part 5: Register the entity. */
+ if (vdev->v4l2_dev && vdev->v4l2_dev->mdev) {
+ vdev->entity.type = MEDIA_ENTITY_TYPE_NODE;
+ vdev->entity.subtype = MEDIA_ENTITY_SUBTYPE_NODE_V4L;
+ vdev->entity.name = vdev->name;
+ vdev->entity.v4l.major = VIDEO_MAJOR;
+ vdev->entity.v4l.minor = vdev->minor;
+ ret = media_device_register_entity(vdev->v4l2_dev->mdev,
+ &vdev->entity);
+ if (ret < 0)
+ printk(KERN_ERR "error\n"); /* TODO */
+ }
+
+ /* Part 6: Activate this minor. The char device can now be used. */
set_bit(V4L2_FL_REGISTERED, &vdev->flags);
mutex_lock(&videodev_lock);
video_device[vdev->minor] = vdev;
mutex_unlock(&videodev_lock);
+
return 0;
cleanup:
@@ -595,6 +623,9 @@ void video_unregister_device(struct video_device *vdev)
if (!vdev || !video_is_registered(vdev))
return;
+ if (vdev->v4l2_dev && vdev->v4l2_dev->mdev)
+ media_device_unregister_entity(&vdev->entity);
+
clear_bit(V4L2_FL_REGISTERED, &vdev->flags);
device_unregister(&vdev->dev);
}
diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
index 195fa56..447b154 100644
--- a/include/media/v4l2-dev.h
+++ b/include/media/v4l2-dev.h
@@ -16,6 +16,8 @@
#include <linux/mutex.h>
#include <linux/videodev2.h>
+#include <media/media-entity.h>
+
#define VIDEO_MAJOR 81
#define VFL_TYPE_GRABBER 0
@@ -57,6 +59,8 @@ struct v4l2_file_operations {
struct video_device
{
+ struct media_entity entity;
+
/* device ops */
const struct v4l2_file_operations *fops;
@@ -96,6 +100,8 @@ struct video_device
const struct v4l2_ioctl_ops *ioctl_ops;
};
+#define media_entity_to_video_device(entity) \
+ container_of(entity, struct video_device, entity)
/* dev to video-device */
#define to_video_device(cd) container_of(cd, struct video_device, dev)
--
1.7.1
--
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