linux-kernel - [PATCH RESEND v2 1/8] media: uvc: Extend documentation of uvc_video_clock

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Message-Id: <20220920-resend-hwtimestamp-v2-1-0d7978a817cc@chromium.org>
Date:   Fri, 02 Dec 2022 18:02:41 +0100
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     "hn.chen" <hn.chen@...plusit.com>, linux-media@...r.kernel.org,
        Ricardo Ribalda <ribalda@...omium.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH RESEND v2 1/8] 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.

Tested-by: HungNien Chen <hn.chen@...plusit.com>
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 170a008f4006..ab56e65ca324 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -517,6 +517,9 @@ 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)

-- 
2.39.0.rc0.267.gcb52ba06e7-goog-b4-0.11.0-dev-696ae