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

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Date:   Wed, 24 Mar 2021 11:01:12 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Ricardo Ribalda <ribalda@...omium.org>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Tomasz Figa <tfiga@...omium.org>,
        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 (21/03/23 17:16), Ricardo Ribalda wrote:
[..]
> > +static bool validate_roi_bounds(struct uvc_streaming *stream,
> > +                               struct v4l2_selection *sel)
> > +{
> > +       if (sel->r.left > USHRT_MAX ||
> > +           sel->r.top > USHRT_MAX ||
> > +           (sel->r.width + sel->r.left) > USHRT_MAX ||
> > +           (sel->r.height + sel->r.top) > USHRT_MAX ||
> > +           !sel->r.width || !sel->r.height)
> > +               return false;
> > +
> > +       if (sel->flags > V4L2_SEL_FLAG_ROI_AUTO_HIGHER_QUALITY)
> > +               return false;
> 
> Is it not allowed V4L2_SEL_FLAG_ROI_AUTO_IRIS |
> V4L2_SEL_FLAG_ROI_AUTO_HIGHER_QUALITY   ?

Good question.

I don't know. Depends on what HIGHER_QUALITY can stand for (UVC doesn't
specify). But overall it seems like features there are mutually
exclusive. E.g. AUTO_FACE_DETECT and AUTO_DETECT_AND_TRACK.


I think it'll be better to replace this with

	if (sel->flags > USHRT_MAX)
		return false;

so that we don't let overflow happen and accidentally enable/disable
some of the features.

> > +
> > +       return true;
> > +}
> > +
> > +static int uvc_ioctl_s_roi(struct file *file, void *fh,
> > +                          struct v4l2_selection *sel)
> > +{
> > +       struct uvc_fh *handle = fh;
> > +       struct uvc_streaming *stream = handle->stream;
> > +       struct uvc_roi_rect *roi;
> > +       int ret;
> > +
> > +       if (!validate_roi_bounds(stream, sel))
> > +               return -E2BIG;
> 
> Not sure if this is the correct approach or if we should convert the
> value to the closest valid...

Well, at this point we know that ROI rectangle dimensions are out of
sane value range. I'd rather tell user-space about integer overflow.

Looking for the closest ROI rectangle that suffice can be rather
tricky. It may sounds like we can just use BOUNDARIES_MAX, but this
is what Firmware D returns for GET_MAX

ioctl(V4L2_SEL_TGT_ROI_BOUNDS_MAX)

	0, 0, 65535, 65535

	-ss