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From:   Ricardo Ribalda <ribalda@chromium.org>
Date:   Thu, 03 Nov 2022 14:40:42 +0100
Subject: [PATCH v2 1/8] media: uvc: Extend documentation of uvc_video_clock_decode()
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Message-Id: <20220920-resend-hwtimestamp-v2-1-d8d0616bb612@chromium.org>
References: <20220920-resend-hwtimestamp-v2-0-d8d0616bb612@chromium.org>
In-Reply-To: <20220920-resend-hwtimestamp-v2-0-d8d0616bb612@chromium.org>
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>
Cc:     HungNien Chen <hn.chen@sunplusit.com>,
        linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
        Ricardo Ribalda <ribalda@chromium.org>
Precedence: bulk

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@sunplusit.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>

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)

-- 
b4 0.11.0-dev-d93f8