linux-kernel - Re: [PATCHv3 5/6] media: uvcvideo: add UVC 1.5 ROI control

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Message-ID: <YFqsZXUuQP9H+Cud@google.com>
Date:   Wed, 24 Mar 2021 12:05:09 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Tomasz Figa <tfiga@...omium.org>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Ricardo Ribalda <ribalda@...omium.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv3 5/6] media: uvcvideo: add UVC 1.5 ROI control

On (21/03/24 12:00), Tomasz Figa wrote:
[..]
> > I guess in our case we need to talk about rectangle,auto-controls tuple
> > that we send to firmware
> >
> >         rect {
> >                 (0, 0), (INT_MAX, INT_MAX)
> >         }
> >         auto-controls {
> >                 INT_MAX
> >         }
> >
> > For ROI user-space also must provide valid auto-controls value, which
> > normally requires GET_MIN/GET_MAX discovery.
> >
> > v4l2 selection API mentions only rectangle adjustments and errnos like
> > -ERANGE also mention "It is not possible to adjust struct v4l2_rect r
> > rectangle to satisfy all constraints given in the flags argument".
> >
> > So in case when auto-controls is out of supported range (out of
> > GET_MIN, GET_MAX range) there is no way for us to tell user-space that
> > auto-controls is wrong. We probably need silently pick up the first
> > supported value, but not sure how well this will work out in the end.
> 
> Shouldn't the autocontrol selection be done via a separate bitmask
> control rather than some custom flags in the selection API?

That selection must be done before we send ROI to the firmware.
Firmware H that I have supports split controls - we can send
ROI::rectangle and ROI::autocontrols separately. But other
firmwares don't tolerate such a thing and by the time we issue

	uvc_query_ctrl(stream->dev,
	               UVC_SET_CUR
	               UVC_CT_REGION_OF_INTEREST_CONTROL
		       roi,
+                      sizeof(struct uvc_roi_rect))

roi rectangle should be of size 5 * u16 and contain values that firmware
will accept, including autocontrols.