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

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Date:   Thu, 15 Aug 2019 16:14:38 +0200
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Jacopo Mondi <jacopo@...ndi.org>
Cc:     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

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.

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.

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.
>>
>