Hi Ralf, On Fri, Jan 02, 2026 at 02:24:20PM +0100, Ralf Jung wrote: > Hi all, > > I did a (lengthy) bisect session, and came out with this commit:
Thanks for doing so and for the time invested! > 52fbe173baa4df9d14bd733f42ee6b9ceab8299b is the first bad commit > commit 52fbe173baa4df9d14bd733f42ee6b9ceab8299b (HEAD) > Author: Ricardo Ribalda <[email protected]> > 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 <[email protected]> > Signed-off-by: Ricardo Ribalda <[email protected]> > Reviewed-by: Laurent Pinchart <[email protected]> > Reviewed-by: Hans de Goede <[email protected]> > Link: > https://lore.kernel.org/r/[email protected] > Signed-off-by: Laurent Pinchart <[email protected]> > Signed-off-by: Mauro Carvalho Chehab <[email protected]> > > 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. You can create a modprobe.d file /etc/modprobe.d/uvcvideo.conf with options uvcvideo nodrop=0 to pass 'nodrop=0' parameter when loading the uvcvideo module (then unload and load the module). But it already warns in dmesg when doing so with: uvcvideo: [Deprecated]: nodrop parameter will be eventually removed. Regards, Salvatore
