linux-kernel - Re: [RFC 2/5] media: v4l2-ctrl: Document V4L2_CID

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Message-ID: <02b40da5-c30c-f1f3-2351-c04da932e94a@xs4all.nl>
Date:   Thu, 15 Aug 2019 15:30:59 +0200
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Jacopo Mondi <jacopo@...ndi.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     "open list:MEDIA INPUT INFRASTRUCTURE (V4L/DVB)" 
        <linux-media@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 2/5] media: v4l2-ctrl: Document V4L2_CID_LOCATION

On 8/14/19 10:28 PM, Jacopo Mondi wrote:
> Add documentation for the V4L2_CID_LOCATION camera control. The newly
> added read-only control reports the camera device mounting position.
> 
> Signed-off-by: Jacopo Mondi <jacopo@...ndi.org>
> ---
>  .../media/uapi/v4l/ext-ctrls-camera.rst       | 23 +++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/Documentation/media/uapi/v4l/ext-ctrls-camera.rst b/Documentation/media/uapi/v4l/ext-ctrls-camera.rst
> index 51c1d5c9eb00..fc0a02eee6d4 100644
> --- a/Documentation/media/uapi/v4l/ext-ctrls-camera.rst
> +++ b/Documentation/media/uapi/v4l/ext-ctrls-camera.rst
> @@ -510,6 +510,29 @@ enum v4l2_scene_mode -
>      value down. A value of zero stops the motion if one is in progress
>      and has no effect otherwise.
> 
> +``V4L2_CID_LOCATION (integer)``
> +    This read-only control describes the camera location by reporting its
> +    mounting position on the device where the camera is installed. This
> +    control is particularly meaningful for devices which have a well defined
> +    orientation, such as phones, laptops and portable devices as the camera
> +    location is expressed as a position relative to the device intended
> +    usage position. In example, a camera installed on the user-facing side
> +    of a phone device is said to be installed in the ``V4L2_LOCATION_FRONT``
> +    position.

When should this control be created? If there is only one location (e.g.
all sensors are front-facing) would you still expose this? Or does it depend
on the type of device?

And is the sensor in a digital camera front or back facing? (Just curious
about what you think about that situation!)

Regards,

	Hans

> +
> +
> +
> +.. flat-table::
> +    :header-rows:  0
> +    :stub-columns: 0
> +
> +    * - ``V4L2_LOCATION_FRONT``
> +      - The camera device is located on the front side of the device.
> +    * - ``V4L2_LOCATION_BACK``
> +      - The camera device is located on the back side of the device.
> +
> +
> +
>  .. [#f1]
>     This control may be changed to a menu control in the future, if more
>     options are required.
> --
> 2.22.0
>