On 11.04.23 14:06, Laurent Pinchart wrote:
> Hi Thorsten,
>
> On Tue, Apr 11, 2023 at 01:49:03PM +0200, Thorsten Leemhuis wrote:
>> On 29.03.23 14:28, Hans Verkuil wrote:
>>> If the fcc is 0 (indicating an unknown GUID format), then fill in the
>>> description field in ENUM_FMT. Otherwise the V4L2 core will WARN.
>>>
>>> Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
>>> Fixes: 50459f103edf ("media: uvcvideo: Remove format descriptions")
>>
>> Thx for working on this.
>>
>> Would be good to have Reported-by and Link tags for any reports about
>> the issue; I'm aware of the following two, maybe there were more:
>>
>> https://bugzilla.kernel.org/show_bug.cgi?id=217252
>> https://bugzilla.redhat.com/show_bug.cgi?id=2180107
>>
>> And a Cc: <stable@xxxxxxxxxxxxxxx> # 5.15.x would likely be good as
>> well, as the culprit was backported.
>>
>> But I write for a different reason: how urgent is this fix? Is this
>> "just" fixing a kernel warning, or do users notice this as some apps
>> crash? The bugzilla.redhat.com ticket's subject indicates it's the
>> latter; and I think I saw someone else mentioning that this leads to
>> crashes, but maybe I'm mixing things up.
>>
>> Because if this fixes a crash, it afaics would be good to get this fixed
>> rather sooner than later in mainline, so that it can be fixed in stable
>> as well.
>
> As far as I understand, it fixes a WARN_ON(). That's technically not a
> crash, but it looks like a big scary one to anyone watching the kernel
> log.
Thx for clarifying. I know what WARN_ON() does, but for some reason was
under the strong impression that one of the reports mentioned the video
app was crashing in parallel to the kernel warning. Well, guess I mixed
this up with some other regression. Sorry for the noise!
Ciao, Thorsten
>>> ---
>>> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
>>> index 7aefa76a42b3..2f1ced1212cd 100644
>>> --- a/drivers/media/usb/uvc/uvc_driver.c
>>> +++ b/drivers/media/usb/uvc/uvc_driver.c
>>> @@ -256,6 +256,9 @@ static int uvc_parse_format(struct uvc_device *dev,
>>> } else {
>>> dev_info(&streaming->intf->dev,
>>> "Unknown video format %pUl\n", &buffer[5]);
>>> + snprintf(format->name, sizeof(format->name), "%pUl\n",
>>> + &buffer[5]);
>>> +
>>> format->fcc = 0;
>>> }
>>>
>>> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
>>> index 35453f81c1d9..fc6f9e7d8506 100644
>>> --- a/drivers/media/usb/uvc/uvc_v4l2.c
>>> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
>>> @@ -713,6 +713,10 @@ static int uvc_ioctl_enum_fmt(struct uvc_streaming *stream,
>>> if (format->flags & UVC_FMT_FLAG_COMPRESSED)
>>> fmt->flags |= V4L2_FMT_FLAG_COMPRESSED;
>>> fmt->pixelformat = format->fcc;
>>> + if (format->name[0])
>>> + strscpy(fmt->description, format->name,
>>> + sizeof(fmt->description));
>>> +
>>> return 0;
>>> }
>>>
>>> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
>>> index 9a596c8d894a..22656755a801 100644
>>> --- a/drivers/media/usb/uvc/uvcvideo.h
>>> +++ b/drivers/media/usb/uvc/uvcvideo.h
>>> @@ -264,6 +264,8 @@ struct uvc_format {
>>> u32 fcc;
>>> u32 flags;
>>>
>>> + char name[32];
>>> +
>>> unsigned int nframes;
>>> struct uvc_frame *frame;
>>> };
>
