Re: [PATCH 2/3] media: videodev2: add a flag for vdev-centric devices

Hans Verkuil
2017-08-25T09:44:30Z

On 08/25/2017 11:40 AM, Mauro Carvalho Chehab wrote:
> From: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
>
> As both vdev-centric and mc-centric devices may implement the
> same APIs, we need a flag to allow userspace to distinguish
> between them.
>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
> ---
> Documentation/media/uapi/v4l/open.rst | 6 ++++++
> Documentation/media/uapi/v4l/vidioc-querycap.rst | 4 ++++
> include/uapi/linux/videodev2.h | 2 ++
> 3 files changed, 12 insertions(+)
>
> diff --git a/Documentation/media/uapi/v4l/open.rst b/Documentation/media/uapi/v4l/open.rst
> index a72d142897c0..eb3f0ec57edb 100644
> --- a/Documentation/media/uapi/v4l/open.rst
> +++ b/Documentation/media/uapi/v4l/open.rst
> @@ -33,6 +33,12 @@ For **vdev-centric** control, the device and their corresponding hardware
> pipelines are controlled via the **V4L2 device** node. They may optionally
> expose via the :ref:`media controller API <media_controller>`.
>
> +.. note::
> +
> + **vdev-centric** devices should report V4L2_VDEV_CENTERED

You mean CENTRIC, not CENTERED.

But I would change this to MC_CENTRIC: the vast majority of drivers are VDEV centric,
so it makes a lot more sense to keep that as the default and only set the cap for
MC-centric drivers.

Regards,

Hans

> + :c:type:`v4l2_capability` flag (see :ref:`VIDIOC_QUERYCAP`).
> +
> +
> For **MC-centric** control, before using the V4L2 device, it is required to
> set the hardware pipelines via the
> :ref:`media controller API <media_controller>`. For those devices, the
> diff --git a/Documentation/media/uapi/v4l/vidioc-querycap.rst b/Documentation/media/uapi/v4l/vidioc-querycap.rst
> index 12e0d9a63cd8..4856821b7608 100644
> --- a/Documentation/media/uapi/v4l/vidioc-querycap.rst
> +++ b/Documentation/media/uapi/v4l/vidioc-querycap.rst
> @@ -252,6 +252,10 @@ specification the ioctl returns an ``EINVAL`` error code.
> * - ``V4L2_CAP_TOUCH``
> - 0x10000000
> - This is a touch device.
> + * - ``V4L2_VDEV_CENTERED``
> + - 0x20000000
> + - This is controlled via V4L2 device nodes (radio, video, vbi,
> + sdr
> * - ``V4L2_CAP_DEVICE_CAPS``
> - 0x80000000
> - The driver fills the ``device_caps`` field. This capability can
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 45cf7359822c..d89090d99042 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -460,6 +460,8 @@ struct v4l2_capability {
>
> #define V4L2_CAP_TOUCH 0x10000000 /* Is a touch device */
>
> +#define V4L2_CAP_VDEV_CENTERED 0x20000000 /* V4L2 Device is controlled via V4L2 device devnode */
> +
> #define V4L2_CAP_DEVICE_CAPS 0x80000000 /* sets device capabilities field */
>
> /*
>