linux-kernel - [PATCH 1/3] media: uvc: Extend documentation of uvc_video_clock

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Message-Id: <20210915200525.448941-2-ribalda@chromium.org>
Date:   Wed, 15 Sep 2021 22:05:23 +0200
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        hn.chen@...plusit.com
Cc:     Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH 1/3] media: uvc: Extend documentation of uvc_video_clock_decode()

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

Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 drivers/media/usb/uvc/uvc_video.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index e16464606b14..77f4090f27d2 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -505,6 +505,9 @@ 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.
+	 * This filtering is also needed for supporting UVC 1.5. Where all the
+	 * data packages 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)
-- 
2.33.0.309.g3052b89438-goog