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Subject: Re: [PATCHv4 0/5] media: uvcvideo: implement UVC 1.5 ROI
To:     Sergey Senozhatsky <senozhatsky@chromium.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Ricardo Ribalda <ribalda@chromium.org>
Cc:     Tomasz Figa <tfiga@chromium.org>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20210430112611.475039-1-senozhatsky@chromium.org>
From:   Hans Verkuil <hverkuil-cisco@xs4all.nl>
Message-ID: <8a175117-d142-9265-65ee-43302bb82444@xs4all.nl>
Date:   Fri, 30 Apr 2021 14:49:00 +0200
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Hi Sergey,

On 30/04/2021 13:26, Sergey Senozhatsky wrote:
> Hello,
> 
> 	This patch set implements UVC 1.5 ROI using v4l2_selection API.

Is the selection API the right approach for this? Wouldn't it make
sense to use controls instead? That would interface easily with the Request
API allowing per-frame changes to the ROI, and with dynamic array controls (1)
it allows you to provide multiple ROIs as well.

The only missing piece would be MIN/MAX for compound controls, but that can
easily be added to the control framework.

If this was discussed before, then can you give a me pointer to that discussion?
I couldn't find anything for that, but I didn't look very long for it :-)

In any case, it doesn't really feel like it is the right API for this job.
I really need to review this series when I have a bit more time :-(

Regards,

	Hans

(1) https://patchwork.linuxtv.org/project/linux-media/cover/20210428101841.696059-1-hverkuil-cisco@xs4all.nl/

> 
> v4:
> -- split ROI rect selection API and auto-controls
> -- handle very large ROI rectangles: limit to frame dimensions
> 
> Sergey Senozhatsky (5):
>   media: v4l UAPI: add ROI selection targets
>   media: v4l UAPI: document ROI selection targets
>   media: uvcvideo: add ROI auto controls
>   media: v4l UAPI: document ROI auto_controls
>   media: uvcvideo: add UVC 1.5 ROI control
> 
>  .../media/v4l/ext-ctrls-camera.rst            |  23 +++
>  .../media/v4l/selection-api-configuration.rst |  22 +++
>  .../media/v4l/selection-api-examples.rst      |  27 +++
>  .../media/v4l/v4l2-selection-targets.rst      |  24 +++
>  drivers/media/usb/uvc/uvc_ctrl.c              |  19 ++
>  drivers/media/usb/uvc/uvc_v4l2.c              | 185 +++++++++++++++++-
>  include/uapi/linux/usb/video.h                |   1 +
>  include/uapi/linux/v4l2-common.h              |   8 +
>  include/uapi/linux/v4l2-controls.h            |   9 +
>  9 files changed, 315 insertions(+), 3 deletions(-)
>