V4L/DVB (10650): uvcvideo: Initialize streaming parameters with the probe control value

The UVC specification requires SET_CUR requests on the streaming commit control
to use values retrieved from a successful GET_CUR request on the probe control.
Initialize streaming parameters with the probe control current value to make
sure the driver always complies.

Signed-off-by: Laurent Pinchart <laurent.pinchart@skynet.be>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 13 insertions, 4 deletions

diff --git a/drivers/media/video/uvc/uvc_video.c b/drivers/media/video/uvc/uvc_video.c
index 7ebb89539c36..9139086f940a 100644
--- a/drivers/media/video/uvc/uvc_video.c
+++ b/drivers/media/video/uvc/uvc_video.c
@@ -1026,11 +1026,20 @@ int uvc_video_init(struct uvc_video_device *video)
          */
         usb_set_interface(video->dev->udev, video->streaming->intfnum, 0);
 
-        /* Some webcams don't suport GET_DEF requests on the probe control. We
-         * fall back to GET_CUR if GET_DEF fails.
+        /* Set the streaming probe control with default streaming parameters
+         * retrieved from the device. Webcams that don't suport GET_DEF
+         * requests on the probe control will just keep their current streaming
+         * parameters.
          */
-        if ((ret = uvc_get_video_ctrl(video, probe, 1, GET_DEF)) < 0 &&
-            (ret = uvc_get_video_ctrl(video, probe, 1, GET_CUR)) < 0)
+        if (uvc_get_video_ctrl(video, probe, 1, GET_DEF) == 0)
+                uvc_set_video_ctrl(video, probe, 1);
+
+        /* Initialize the streaming parameters with the probe control current
+         * value. This makes sure SET_CUR requests on the streaming commit
+         * control will always use values retrieved from a successful GET_CUR
+         * request on the probe control, as required by the UVC specification.
+         */
+        if ((ret = uvc_get_video_ctrl(video, probe, 1, GET_CUR)) < 0)
                 return ret;
 
         /* Check if the default format descriptor exists. Use the first