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

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Date:   Thu, 15 Aug 2019 16:34:23 +0200
From:   Jacopo Mondi <jacopo@...ndi.org>
To:     Hans Verkuil <hverkuil-cisco@...all.nl>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        "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

Hi Hans,

On Thu, Aug 15, 2019 at 04:14:38PM +0200, Hans Verkuil wrote:
> On 8/15/19 4:10 PM, Hans Verkuil wrote:
> > On 8/15/19 12:43 AM, Laurent Pinchart wrote:
> >> Hi Jacopo,
> >>
> >> Thank you for the patch.
> >>
> >> 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@...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)``
> >>
> >> Maybe V4L2_CID_CAMERA_SENSOR_LOCATION ? Same for the values below.
> >
> > Probably a better name, if a bit long. But we might need other location
> > controls in the future (e.g. flash location), so CID_LOCATION is just too
> > generic.
>

Thanks for the feedback.

> Note that the location defines themselves can most likely be used with any
> LOCATION control, so V4L2_LOCATION_FRONT would be fine with any control.
>

What do you think instead of the control type? Would a single integer
control do or an integer menu one would be better? I see merit in both
proposals actually...

Once this is clarified, I can send a proper v1.

Thanks
  j

> Regards,
>
> 	Hans
>
> >
> > Regards,
> >
> > 	Hans
> >
> >>
> >>> +    This read-only control describes the camera location by reporting its
> >>
> >> Here too I would mention camera sensor instead of just camera (or
> >> possibly imaging sensor).
> >>
> >>> +    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.
> >>
> >> The DT bindings could use such an example :-) I would extend this to
> >> tablets and laptops.
> >>
> >>> +
> >>> +
> >>> +
> >>
> >> Do we need three blank lines ?
> >>
> >>> +.. 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.
> >>
> >
>

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