path: root/drivers
diff options
authorAviv Greenberg <aviv.d.greenberg@intel.com>2014-09-02 03:16:28 -0300
committerMauro Carvalho Chehab <mchehab@osg.samsung.com>2015-01-27 10:39:17 -0200
commit9fae30acdeefb8955c9f90d4d18a3d1dc599a1ff (patch)
treec37555433cce6e07edf9e6fddbd0ee70cd8ef8aa /drivers
parent533ab2231d15e082f4ef547ee2fe99a8a25ab046 (diff)
[media] uvcvideo: Remove extra commit on resume()
The UVC spec is a bit vague wrt devices using bulk endpoints, specifically, how to signal to a device to start streaming. For devices using isoc endpoints, the sequence for start streaming is: 1) The host sends PROBE_CONTROL(SET_CUR) PROBE_CONTROL(GET_CUR) 2) Host selects desired config and calls COMMIT_CONTROL(SET_CUR) 3) Host selects an alt interface other then zero - e.g SELECT_ALTERNATE_INTERFACE(1) 4) The device starts streaming However for devices using bulk endpoints, there must be *no* alt interface other than setting zero. From the UVC spec: "A VideoStreaming interface containing a bulk endpoint for streaming shall support only alternate setting zero. Additional alternate settings containing bulk endpoints are not permitted in a device that is compliant with the Video Class specification." So for devices using bulk endpoints, step #3 above is irrelevant, and thus cannot be used as an indication for the device to start streaming. So in practice, such devices start streaming immediately after a COMMIT_CONTROL(SET_CUR). In the uvc resume() handler, an unsolicited commit is sent, which causes devices using bulk endpoints to start streaming unintentionally. This patch modifies resume() handler to send a commit only if streaming needs to be reestablished, i.e if the device was actually streaming before is was suspended. Signed-off-by: Aviv Greenberg <aviv.d.greenberg@intel.com> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Diffstat (limited to 'drivers')
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index 9637e8b86949..20ccc9d315dc 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -1734,13 +1734,13 @@ int uvc_video_resume(struct uvc_streaming *stream, int reset)
+ if (!uvc_queue_streaming(&stream->queue))
+ return 0;
ret = uvc_commit_video(stream, &stream->ctrl);
if (ret < 0)
return ret;
- if (!uvc_queue_streaming(&stream->queue))
- return 0;
return uvc_init_video(stream, GFP_NOIO);

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