Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes)

From	Ralf Jung <post@ralfj.de>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes)
Date	2026-01-02 14:30 +0100
Message-ID	<M8No5-7w8Q-19@gated-at.bofh.it> (permalink)
References	(4 earlier) <LZOt3-1nN7-7@gated-at.bofh.it> <M2ZBD-3A7N-7@gated-at.bofh.it> <M3lst-3Pol-9@gated-at.bofh.it> <LX8xX-h7QL-1@gated-at.bofh.it> <M3lst-3Pol-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Cross-posted to 2 groups.

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Hi all,

I did a (lengthy) bisect session, and came out with this commit:

52fbe173baa4df9d14bd733f42ee6b9ceab8299b is the first bad commit
commit 52fbe173baa4df9d14bd733f42ee6b9ceab8299b (HEAD)
Author: Ricardo Ribalda <ribalda@chromium.org>
Date:   Wed Dec 18 21:39:09 2024 +0000

     media: uvcvideo: Invert default value for nodrop module param

     The module param `nodrop` defines what to do with frames that contain an
     error: drop them or sending them to userspace.

     The default in the rest of the media subsystem is to return buffers with
     an error to userspace with V4L2_BUF_FLAG_ERROR set in v4l2_buffer.flags.
     In UVC we drop buffers with errors by default.

     Change the default behaviour of uvcvideo to match the rest of the
     drivers and maybe get rid of the module parameter in the future.

     Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
     Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
     Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
     Reviewed-by: Hans de Goede <hdegoede@redhat.com>
     Link: 
https://lore.kernel.org/r/20241218-uvc-deprecate-v2-2-ab814139e983@chromium.org
     Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
     Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

  drivers/media/usb/uvc/uvc_driver.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

I added Ricardo in Cc. Ricardo, see 
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1121718 for context.

The bug does not always immediately manifest, so there is a small chance that 
for some of the commits that I marked "good", artifacts would have started 
appearing if I had waited a bit longer. But the commit seems reasonably 
plausible to be able to cause the kind of error I am seeing.

Given that this is about a module parameter, I assume I could test this by 
booting the latest kernel and setting the parameter back to its previous 
value... but I don't know enough about how the kernel works to actually do 
that.^^ Happy to try that if someone gives me some pointers.

Kind regards,
Ralf

Thread

Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Salvatore Bonaccorso <carnil@debian.org> - 2025-12-02 17:50 +0100
  Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-02 18:50 +0100
    Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-08 19:50 +0100
    Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-17 14:20 +0100
      Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Salvatore Bonaccorso <carnil@debian.org> - 2025-12-17 20:30 +0100
        Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-17 20:40 +0100
          Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-18 14:20 +0100
      Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-02 14:30 +0100
        Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Salvatore Bonaccorso <carnil@debian.org> - 2026-01-02 15:10 +0100
          Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-02 17:40 +0100
            Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-05 16:50 +0100
            Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Laurent Pinchart <laurent.pinchart@ideasonboard.com> - 2026-01-05 19:10 +0100
            Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-05 20:30 +0100
              Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-20 15:30 +0100

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