From 9fae30acdeefb8955c9f90d4d18a3d1dc599a1ff Mon Sep 17 00:00:00 2001 From: Aviv Greenberg Date: Tue, 2 Sep 2014 03:16:28 -0300 Subject: [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 Signed-off-by: Guennadi Liakhovetski Signed-off-by: Laurent Pinchart Signed-off-by: Mauro Carvalho Chehab diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c index 9637e8b..20ccc9d 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) uvc_video_clock_reset(stream); + 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); } -- cgit v0.10.2