When you start streaming from uvc, then the first buffer will
have sequence number 0 and the second buffer has sequence number
2. Fix the logic to ensure proper monotonically increasing sequence
numbers.
The root cause is not setting last_fid when you start streaming
and a new fid is found for the first time.
This patch also changes the initial last_fid value from -1 to 0xff.
Since last_fid is unsigned, it is better to stick to unsigned values.
Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
---
drivers/media/usb/uvc/uvc_video.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index 9f37eaf28ce7..8ba8d25e2c4a 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -1055,7 +1055,10 @@ static int uvc_video_decode_start(struct uvc_streaming *stream,
* that discontinuous sequence numbers always indicate lost frames.
*/
if (stream->last_fid != fid) {
- stream->sequence++;
+ if (stream->last_fid > UVC_STREAM_FID)
+ stream->last_fid = fid;
+ else
+ stream->sequence++;
if (stream->sequence)
uvc_video_stats_update(stream);
}
@@ -1080,7 +1083,7 @@ static int uvc_video_decode_start(struct uvc_streaming *stream,
/* Synchronize to the input stream by waiting for the FID bit to be
* toggled when the the buffer state is not UVC_BUF_STATE_ACTIVE.
- * stream->last_fid is initialized to -1, so the first isochronous
+ * stream->last_fid is initialized to 0xff, so the first isochronous
* frame will always be in sync.
*
* If the device doesn't toggle the FID bit, invert stream->last_fid
@@ -1111,7 +1114,7 @@ static int uvc_video_decode_start(struct uvc_streaming *stream,
* last payload can be lost anyway). We thus must check if the FID has
* been toggled.
*
- * stream->last_fid is initialized to -1, so the first isochronous
+ * stream->last_fid is initialized to 0xff, so the first isochronous
* frame will never trigger an end of frame detection.
*
* Empty buffers (bytesused == 0) don't trigger end of frame detection
@@ -1895,7 +1898,7 @@ static int uvc_video_start_transfer(struct uvc_streaming *stream,
int ret;
stream->sequence = -1;
- stream->last_fid = -1;
+ stream->last_fid = 0xff;
stream->bulk.header_size = 0;
stream->bulk.skip_payload = 0;
stream->bulk.payload_size = 0;
--
2.33.0
