linux-kernel - Re: [PATCHv4 0/5] media: uvcvideo: implement UVC 1.5 ROI

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Date:   Sat, 1 May 2021 10:58:10 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Hans Verkuil <hverkuil-cisco@...all.nl>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Ricardo Ribalda <ribalda@...omium.org>,
        Tomasz Figa <tfiga@...omium.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4 0/5] media: uvcvideo: implement UVC 1.5 ROI

Hi Hans,

On (21/04/30 14:49), Hans Verkuil wrote:
> 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?

[..]

> 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 :-)

I believe Tomasz raised this question over IRC back in the days and there
was no clear conclusion at the end: selection API vs control - 50/50 split.
After internal discussions we decided to go with the selection API.

> In any case, it doesn't really feel like it is the right API for this job.

Well, we pass a rectangle to the driver. The driver already knows what
to do with some of those rectangles, we teach it to handle one more. So
we don't introduce anything new, but use the existing API instead.