linux-kernel - [PATCH v11] media: uvcvideo: Fix bandwidth issue for Alcor camera.

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Message-Id: <20250515111406.1470687-1-ccc194101@163.com>
Date: Thu, 15 May 2025 19:14:06 +0800
From: chenchangcheng <ccc194101@....com>
To: laurent.pinchart@...asonboard.com,
	ribalda@...omium.org
Cc: hdegoede@...hat.com,
	mchehab@...nel.org,
	linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	chenchangcheng <chenchangcheng@...inos.cn>
Subject: [PATCH v11] media: uvcvideo: Fix bandwidth issue for Alcor camera.

From: chenchangcheng <chenchangcheng@...inos.cn>

Some broken device return wrong dwMaxPayloadTransferSize fields
as follows:
    [  218.632537] [pid:20427,cpu6,guvcview,8]uvcvideo: Device requested 2752512 B/frame bandwidth.
    [  218.632598] [pid:20427,cpu6,guvcview,9]uvcvideo: No fast enough alt setting for requested bandwidth.

When dwMaxPayloadTransferSize is greater than maxpsize,
it will prevent the camera from starting.
So use the bandwidth of maxpsize.

Signed-off-by: chenchangcheng <chenchangcheng@...inos.cn>
---
 drivers/media/usb/uvc/uvc_video.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index e3567aeb0007..11769a1832d2 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -262,6 +262,15 @@ static void uvc_fixup_video_ctrl(struct uvc_streaming *stream,
 
 		ctrl->dwMaxPayloadTransferSize = bandwidth;
 	}
+
+	if (stream->intf->num_altsetting > 1 &&
+	    ctrl->dwMaxPayloadTransferSize > stream->maxpsize) {
+		dev_warn_ratelimited(&stream->intf->dev,
+				     "UVC non compliance: the max payload transmission size (%u) exceeds the size of the ep max packet (%u). Using the max size.\n",
+				     ctrl->dwMaxPayloadTransferSize,
+				     stream->maxpsize);
+		ctrl->dwMaxPayloadTransferSize = stream->maxpsize;
+	}
 }
 
 static size_t uvc_video_ctrl_size(struct uvc_streaming *stream)

base-commit: 9f35e33144ae5377d6a8de86dd3bd4d995c6ac65
-- 
2.25.1