Re: [RFC 2/5] media: v4l2-ctrl: Document V4L2_CID_LOCATION

From: Laurent Pinchart
Date: Thu Aug 15 2019 - 08:59:45 EST


Hi Sakari,

On Thu, Aug 15, 2019 at 10:00:25AM +0300, Sakari Ailus wrote:
> On Wed, Aug 14, 2019 at 10:28:12PM +0200, 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@xxxxxxxxxx>
> > ---
> > .../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
>
> s/In/For/
>
> > + of a phone device is said to be installed in the ``V4L2_LOCATION_FRONT``
> > + position.
> > +
> > +
> > +
> > +.. 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.
>
> There's an effective limit of 64 for menus. ACPI has less than ten
> different locations for a device, I think 64 will be enough here.
>
> So I'd be actually in favour of switching to a menu.

Why ? As you explained yourself, it's a static read-only control, all it
needs to report is a single value.

--
Regards,

Laurent Pinchart