[PATCH v8 11/12] v4l: Make video_device inherit from media_entity

Laurent Pinchart
2011-01-27T12:30:54Z

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@maxwell.research.nokia.com>
---
Documentation/video4linux/v4l2-framework.txt | 38 ++++++++++++++++++--
drivers/media/video/v4l2-dev.c | 49 +++++++++++++++++++++++--
include/media/v4l2-dev.h | 7 ++++
3 files changed, 87 insertions(+), 7 deletions(-)

diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt
index aeb2a22..f231bc20 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
@@ -532,6 +539,21 @@ 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
--------------------------------

@@ -561,6 +583,9 @@ 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:

@@ -636,6 +661,13 @@ 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
-----------------------------
diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c
index f22bd41..f91348f 100644
--- a/drivers/media/video/v4l2-dev.c
+++ b/drivers/media/video/v4l2-dev.c
@@ -303,6 +303,9 @@ 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;
+#if defined(CONFIG_MEDIA_CONTROLLER)
+ struct media_entity *entity = NULL;
+#endif
int ret = 0;

/* Check if the video device is available */
@@ -316,6 +319,16 @@ static int v4l2_open(struct inode *inode, struct file *filp)
/* and increase the device refcount */
video_get(vdev);
mutex_unlock(&videodev_lock);
+#if defined(CONFIG_MEDIA_CONTROLLER)
+ if (vdev->v4l2_dev && vdev->v4l2_dev->mdev) {
+ entity = media_entity_get(&vdev->entity);
+ if (!entity) {
+ ret = -EBUSY;
+ video_put(vdev);
+ return ret;
+ }
+ }
+#endif
if (vdev->fops->open) {
if (vdev->lock && mutex_lock_interruptible(vdev->lock)) {
ret = -ERESTARTSYS;
@@ -331,8 +344,13 @@ static int v4l2_open(struct inode *inode, struct file *filp)

err:
/* decrease the refcount in case of an error */
- if (ret)
+ if (ret) {
+#if defined(CONFIG_MEDIA_CONTROLLER)
+ if (vdev->v4l2_dev && vdev->v4l2_dev->mdev)
+ media_entity_put(entity);
+#endif
video_put(vdev);
+ }
return ret;
}

@@ -349,7 +367,10 @@ static int v4l2_release(struct inode *inode, struct file *filp)
if (vdev->lock)
mutex_unlock(vdev->lock);
}
-
+#if defined(CONFIG_MEDIA_CONTROLLER)
+ if (vdev->v4l2_dev && vdev->v4l2_dev->mdev)
+ media_entity_put(&vdev->entity);
+#endif
/* decrease the refcount unconditionally since the release()
return value is ignored. */
video_put(vdev);
@@ -586,12 +607,27 @@ int __video_register_device(struct video_device *vdev, int type, int nr,
if (nr != -1 && nr != vdev->num && warn_if_nr_in_use)
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. */
+#if defined(CONFIG_MEDIA_CONTROLLER)
+ /* Part 5: Register the entity. */
+ if (vdev->v4l2_dev && vdev->v4l2_dev->mdev) {
+ vdev->entity.type = MEDIA_ENT_T_DEVNODE_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_WARNING
+ "%s: media_device_register_entity failed\n",
+ __func__);
+ }
+#endif
+ /* 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:
@@ -619,6 +655,11 @@ void video_unregister_device(struct video_device *vdev)
if (!vdev || !video_is_registered(vdev))
return;

+#if defined(CONFIG_MEDIA_CONTROLLER)
+ if (vdev->v4l2_dev && vdev->v4l2_dev->mdev)
+ media_device_unregister_entity(&vdev->entity);
+#endif
+
mutex_lock(&videodev_lock);
/* This must be in a critical section to prevent a race with v4l2_open.
* Once this bit has been cleared video_get may never be called again.
diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
index 4fe6831..51b2c51 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
@@ -55,6 +57,9 @@ struct v4l2_file_operations {

struct video_device
{
+#if defined(CONFIG_MEDIA_CONTROLLER)
+ struct media_entity entity;
+#endif
/* device ops */
const struct v4l2_file_operations *fops;

@@ -100,6 +105,8 @@ struct video_device
struct mutex *lock;
};

+#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)

--
1.7.3.4