media: uvcvideo: Extend documentation of uvc_video_clock_decode()

Make an explicit reference to UVC 1.5, explaining how the algorithm
supports the different behaviour of UVC 1.1 and 1.5.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: HungNien Chen <hn.chen@sunplusit.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index e4b71df..b1f7416 100644 (file)
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -518,7 +518,9 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
 
        /*
         * To limit the amount of data, drop SCRs with an SOF identical to the
-        * previous one.
+        * previous one. This filtering is also needed to support UVC 1.5, where
+        * all the data packets of the same frame contains the same SOF. In that
+        * case only the first one will match the host_sof.
         */
        dev_sof = get_unaligned_le16(&data[header_size - 2]);
        if (dev_sof == stream->clock.last_sof)