V4L/DVB (9661): uvcvideo: Commit streaming parameters when enabling the video stream
Sonix-based cameras seem to require the host to commit video streaming
parameters before selecting the alternate endpoint. While most applications
issue a VIDIOC_S_FMT ioctl before starting streaming, this is not required
by the V4L2 specification.
The problem has been noticed on Ubuntu 8.10 with applications using libv4l.
The library blocks VIDIOC_S_FMT calls when the requested format is identical
to the currently selected format. As the driver commits video streaming
parameters when initialising the device, only the first run of a
libv4l-enabled application would succeed.
For the sake of completeness, experiment showed that the camera keeps sending
12 bytes isochronous packets (header only, no data) without toggling the FID
bit if video streaming parameters haven't been committed before selecting the
alternate endpoint.
Signed-off-by: Laurent Pinchart <laurent.pinchart@skynet.be>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/uvc/uvc_video.c b/drivers/media/video/uvc/uvc_video.c
index e07bee9..186ef9f 100644
--- a/drivers/media/video/uvc/uvc_video.c
+++ b/drivers/media/video/uvc/uvc_video.c
@@ -889,7 +889,7 @@
video->frozen = 0;
- if ((ret = uvc_set_video_ctrl(video, &video->streaming->ctrl, 0)) < 0) {
+ if ((ret = uvc_commit_video(video, &video->streaming->ctrl)) < 0) {
uvc_queue_enable(&video->queue, 0);
return ret;
}
@@ -970,11 +970,8 @@
break;
}
- /* Commit the default settings. */
probe->bFormatIndex = format->index;
probe->bFrameIndex = frame->bFrameIndex;
- if ((ret = uvc_set_video_ctrl(video, probe, 0)) < 0)
- return ret;
video->streaming->cur_format = format;
video->streaming->cur_frame = frame;
@@ -1014,6 +1011,10 @@
if ((ret = uvc_queue_enable(&video->queue, 1)) < 0)
return ret;
+ /* Commit the streaming parameters. */
+ if ((ret = uvc_commit_video(video, &video->streaming->ctrl)) < 0)
+ return ret;
+
return uvc_init_video(video, GFP_KERNEL);
}