Hi Laurent
I agree with the intent of the patch but am not sure that this will work.
Regards!
On Thu, 20 Apr 2023 at 12:07, Laurent Pinchart
<laurent.pinchart@xxxxxxxxxxxxxxxx> wrote:
>
> When the uvcvideo driver encounters a format descriptor with an unknown
> format GUID, it creates a corresponding struct uvc_format instance with
> the fcc field set to 0. Since commit 50459f103edf ("media: uvcvideo:
> Remove format descriptions"), the driver relies on the V4L2 core to
> provide the format description string, which the V4L2 core can't do
> without a valid 4CC. This triggers a WARN_ON.
>
> As a format with a zero 4CC can't be selected, it is unusable for
> applications. Ignore the format completely without creating a uvc_format
> instance, which fixes the warning.
>
> Fixes: 50459f103edf ("media: uvcvideo: Remove format descriptions")
> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> ---
> drivers/media/usb/uvc/uvc_driver.c | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index de64c9d789fd..25b8199f4e82 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -251,14 +251,17 @@ static int uvc_parse_format(struct uvc_device *dev,
> /* Find the format descriptor from its GUID. */
> fmtdesc = uvc_format_by_guid(&buffer[5]);
>
> - if (fmtdesc != NULL) {
> - format->fcc = fmtdesc->fcc;
> - } else {
> + if (!fmtdesc) {
> + /*
> + * Unknown video formats are not fatal errors, the
> + * caller will skip this descriptor.
> + */
> dev_info(&streaming->intf->dev,
> "Unknown video format %pUl\n", &buffer[5]);
> - format->fcc = 0;
> + return 0;
> }
>
> + format->fcc = fmtdesc->fcc;
> format->bpp = buffer[21];
>
> /*
> @@ -689,6 +692,8 @@ static int uvc_parse_streaming(struct uvc_device *dev,
> &interval, buffer, buflen);
For devices with unknown formats streaming->nformats will not be
valid, it will be higher than the actual formats on
streaming->formats.
> if (ret < 0)
> goto error;
> + if (!ret)
> + break;
>
> frame += format->nframes;
> format++;
> --
> Regards,
>
> Laurent Pinchart
>
--
Ricardo Ribalda
