linux-kernel - Re: [RFC PATCH 0/2] media: v4l2: map UVC_CT_ROLL_ABSOLUTE

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Date:   Fri, 4 Aug 2023 20:45:41 +0200
From:   Michael Riesch <michael.riesch@...fvision.net>
To:     Gergő Köteles <soyer@....hu>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/2] media: v4l2: map UVC_CT_ROLL_ABSOLUTE_CONTROL

Hi Gergő,

Interesting work! I would guess that there are a lot of cameras with an
accelerometer or gyroscope that could report the rotation.

On 8/3/23 23:28, Gergő Köteles wrote:
> Hi,
> 
> Logitech Streamcam can be mounted in 'portrait mode' as well.
> It reports the current roll (-90, 0, 90, 180) with
> UVC_CT_ROLL_ABSOLUTE_CONTROL.
> 
> This RFC defines V4L2_CID_ROLL_ABSOLUTE, and maps
> UVC_CT_ROLL_ABSOLUTE_CONTROL to make it available to
> userspace.
> Then, the userspace can rotate the stream based on the roll.

Should we also discuss pitch and yaw while we are at it?

As far as I know there are controls to set pan and tilt of a PTZ camera,
but there are no controls that report those angles.

> Is it better to use V4L2_CID_CAMERA_SENSOR_ROTATION for this?

IMHO that would make sense.

Best regards,
Michael

> The value set matches that control.
> If yes, is it worth mapping UVC_CT_ROLL_ABSOLUTE_CONTROL to
> V4L2_CID_CAMERA_SENSOR_ROTATION for this camera only?
> 
> Any feedback is greately appreciated.
> 
> 
> Gergő Köteles (2):
>   media: v4l2: ctrls: Add ROLL_ABSOLUTE control
>   media: v4l2: map UVC_CT_ROLL_ABSOLUTE_CONTROL
> 
>  .../userspace-api/media/v4l/ext-ctrls-camera.rst         | 5 +++++
>  drivers/media/usb/uvc/uvc_ctrl.c                         | 9 +++++++++
>  drivers/media/v4l2-core/v4l2-ctrls-defs.c                | 1 +
>  include/uapi/linux/v4l2-controls.h                       | 2 ++
>  4 files changed, 17 insertions(+)
> 
> 
> base-commit: 06c2afb862f9da8dc5efa4b6076a0e48c3fbaaa5