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    Subject[RFC/PATCH v6 11/12] v4l: Make video_device inherit from media_entity
    Date
    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 | 47 +++++++++++++++++++++++---
    include/media/v4l2-dev.h | 7 ++++
    3 files changed, 84 insertions(+), 8 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 035db52..511e1ee 100644
    --- a/drivers/media/video/v4l2-dev.c
    +++ b/drivers/media/video/v4l2-dev.c
    @@ -278,6 +278,9 @@ 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 */
    @@ -291,6 +294,16 @@ 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(vdev->lock);
    @@ -303,8 +316,13 @@ static int v4l2_open(struct inode *inode, struct file *filp)
    }

    /* 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;
    }

    @@ -321,7 +339,10 @@ 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);
    @@ -558,12 +579,25 @@ 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_ENTITY_TYPE_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 */
    + }
    +#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:
    @@ -590,7 +624,10 @@ void video_unregister_device(struct video_device *vdev)
    /* Check if vdev was ever registered at all */
    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
    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 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)

    --
    1.7.2.2


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