From: Kirill A. Korinsky <kirill@korins.ky>
Subject: Re: sys/uvideo: fill v4l2_capability the right way
To: Marcus Glocker <marcus@nazgul.ch>
Cc: tech@openbsd.org
Date: Sat, 28 Dec 2024 23:14:44 +0100

On Sat, 28 Dec 2024 22:39:08 +0100,
Marcus Glocker <marcus@nazgul.ch> wrote:
> 
> On Sat, Dec 28, 2024 at 04:18:57PM GMT, Kirill A. Korinsky wrote:
> 
> > tech@,
> > 
> > Some V4L consumers, for example libwebrtc which is used by firefox, uses
> > bus_info to find the desired webcam.
> > 
> > Our logic with hardcoded string leads that firefox uses /dev/video0, and
> > switch to another webcam simple doesn't work.
> > 
> > This behaviour of Linux uvc_meta_v4l2_querycap which uses constant as
> > driver name, and device as bus_info.
> > 
> > Ok?
> 
> As discussed over the other mails, I'm OK with that after understanding
> the requirement.  I also did run the patch quickly against
> /usr/src/regress/sys/dev/video.
> 
> ok mglocker@
>

Thanks.

Just for context: vidioc-querycap.rst states:

      - ``bus_info``\ [32]
      - Location of the device in the system, a NUL-terminated ASCII
        string. For example: "PCI:0000:05:06.0". This information is
        intended for users, to distinguish multiple identical devices. If
        no such information is available the field must simply count the
        devices controlled by the driver ("platform:vivid-000"). The
        bus_info must start with "PCI:" for PCI boards, "PCIe:" for PCI
        Express boards, "usb-" for USB devices, "I2C:" for i2c devices,
        "ISA:" for ISA devices, "parport" for parallel port devices and
        "platform:" for platform devices.

Probably, we may use platform:uvideo0 to be alligned with this. But I can't
find any software which parses such field. So, just uvideo0 should be safe.

-- 
wbr, Kirill