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[34.88.69.27]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a13d033f96sm2772906e87.34.2026.03.10.04.54.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Mar 2026 04:54:24 -0700 (PDT) From: Ricardo Ribalda Date: Tue, 10 Mar 2026 11:54:24 +0000 Subject: [PATCH] media: uvcvideo: Fix buffer sequence in frame gaps Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260310-uvc-fid-v1-1-5e37dc3c7024@chromium.org> X-B4-Tracking: v=1; b=H4sIAG8GsGkC/6tWKk4tykwtVrJSqFYqSi3LLM7MzwNyDHUUlJIzE vPSU3UzU4B8JSMDIzMDY0MD3dKyZN20zBTdVMNUU1MTE/MkszRDJaDqgqLUtMwKsEnRsbW1AGi dz99ZAAAA X-Change-ID: 20260310-uvc-fid-e1e55447b6f1 To: Laurent Pinchart , Hans de Goede , Mauro Carvalho Chehab Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Yunke Cao , stable@kernel.org, Ricardo Ribalda X-Mailer: b4 0.14.3 In UVC, the FID flips with every frame. For every FID flip, we increase the sequence number. Userpace use that information to figure out if there has been a gap between frames. Now, we only update the sequence number on the first FID flip, which results in frames being incorrectly numbered just after a frame gap. This patch rewrites the sequence number of the buffer in those situations. Cc: stable@kernel.org Fixes: 650b95feee35 ("[media] uvcvideo: Generate discontinuous sequence num= bers when frames are lost") Signed-off-by: Ricardo Ribalda --- drivers/media/usb/uvc/uvc_video.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_= video.c index 40c76c051da2..ec769a504569 100644 --- a/drivers/media/usb/uvc/uvc_video.c +++ b/drivers/media/usb/uvc/uvc_video.c @@ -1176,6 +1176,14 @@ static int uvc_video_decode_start(struct uvc_streami= ng *stream, stream->sequence++; if (stream->sequence) uvc_video_stats_update(stream); + + /* + * If we have not received any data and FID flips, update the + * sequence number of the buffer to tell userspace exactly + * where the frame gap is. + */ + if (buf && !buf->bytesused) + buf->buf.sequence =3D stream->sequence; } =20 uvc_video_clock_decode(stream, buf, data, len); --- base-commit: a7da7fb57f2a787412da1a62292a17fa00fbfbdf change-id: 20260310-uvc-fid-e1e55447b6f1 Best regards, --=20 Ricardo Ribalda