From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from stravinsky.debian.org (stravinsky.debian.org [82.195.75.108]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A60222D97A5; Fri, 2 Jan 2026 14:01:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=82.195.75.108 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767362471; cv=none; b=X33va2oykQVgpFyjH+z3MfbeUOjPWfb1z4jNbFZyZHK6qcVTiTKUnUi29IvIZyiw62v0z2iVdS9EEri5CG3Tl+bCqJRtaB0wTRoT3s+ur13Hn5I+iGVCpGUJ6HRED7it5JoVzGrGukO+j8Yy/ktKbq0WX3G/mHs5pXulAX6mGWo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767362471; c=relaxed/simple; bh=6f2MG+N763IiADhwtWWghtp2dIJe7urQJ8tmH5qnDSc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ucFAbMonykJa7flgAxPKK26uhxNmRAZb3trlhnrSg2zil7QPqtkSW7gPUkBDOHZu8SljLotrbTAVI8jMyI7qLCO3JEAVlaSd31qGlbBdwvFBULQgAD2kV4vY3ZtPBPfCvVji0EqBBEkx/sJB8a7rv+kUtSo7/auK47wVZFCDloo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=debian.org; spf=none smtp.mailfrom=debian.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b=XBTSIrhH; arc=none smtp.client-ip=82.195.75.108 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=debian.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=debian.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b="XBTSIrhH" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=debian.org; s=smtpauto.stravinsky; h=X-Debian-User:In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=GxTLdXWJWS4u8qr5xs+QFAr0R8cHrLMggWmYTExNqlI=; b=XBTSIrhHoZQixMJi9GCkAczn/E UIqD9dN12Swps6F5ZxeI8WwfzTuCnHn0ubWos1NguSY9Z12Y3TfUcTF2l73rrI4h6ptE4T59HAMxL 9Lae/MZ7TBFeo+OFLomQ6owvj4aYMlS4Ql5iTXNfFKQ4ZWSG+ba1fBO03FZfTiur92o8bF/15Gd22 zoJnuGyBWusKQPHLzuldSxiSc0K1oHurh4PeS0NoH3pXA+9LYA0QKw+o+mp3a/O1PvQnrJ2im5Q/D 7dzZy01PTdBKmEFEa2cEbIG+78oo8QN+CopkX/ycDVdpbLybTQXFU+4p6TvHa11Wdkp/1M8yVXnAe tcR+KGgA==; Received: from authenticated user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.94.2) (envelope-from ) id 1vbfi6-00EV4n-2h; Fri, 02 Jan 2026 14:00:58 +0000 Received: by eldamar.lan (Postfix, from userid 1000) id 450D1BE2DE0; Fri, 02 Jan 2026 15:00:57 +0100 (CET) Date: Fri, 2 Jan 2026 15:00:57 +0100 From: Salvatore Bonaccorso To: Ralf Jung , 1121718@bugs.debian.org Cc: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , Ricardo Ribalda , linux-media@vger.kernel.org, regressions@lists.linux.dev, Mauro Carvalho Chehab Subject: Re: Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Message-ID: References: <176458169204.346596.13968096833088921213.reportbug@r-ethtop> <176458169204.346596.13968096833088921213.reportbug@r-ethtop> <4rnbopkefvp6h3dwttj4h7cexehqtbuzzz4gatnebdnjzdy2li@bupytpnlk2xh> <2ed13f74-8de3-4caf-8972-26dd5a31e9fc@ralfj.de> <176458169204.346596.13968096833088921213.reportbug@r-ethtop> <0490a39a-28d9-4925-a162-5e4d498be257@ralfj.de> Precedence: bulk X-Mailing-List: regressions@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0490a39a-28d9-4925-a162-5e4d498be257@ralfj.de> X-Debian-User: carnil 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 > 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 > Signed-off-by: Ricardo Ribalda > Reviewed-by: Laurent Pinchart > Reviewed-by: Hans de Goede > Link: https://lore.kernel.org/r/20241218-uvc-deprecate-v2-2-ab814139e983@chromium.org > Signed-off-by: Laurent Pinchart > Signed-off-by: Mauro Carvalho Chehab > > 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