On Thu, Jul 15, 2021 at 06:00:10PM +0000, Benjamin Drung wrote:
Hi Greg,
thanks for applying/staging the commit for the stable release. For kernel <= 5.11 the patch needs a small modification for the debug log. See below. Should I send an adapted patch to stable@vger.kernel.org to replace this one?
On Thu, 2021-07-15 at 16:43 +0200, gregkh@linuxfoundation.org wrote:
This is a note to let you know that I've just added the patch titled
media: uvcvideo: Fix pixel format change for Elgato Cam Link 4Kto the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: media-uvcvideo-fix-pixel-format-change-for-elgato-cam-link-4k.patch and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 4c6e0976295add7f0ed94d276c04a3d6f1ea8f83 Mon Sep 17 00:00:00 2001 From: Benjamin Drung bdrung@posteo.de Date: Sat, 5 Jun 2021 22:15:36 +0200 Subject: media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K
From: Benjamin Drung bdrung@posteo.de
commit 4c6e0976295add7f0ed94d276c04a3d6f1ea8f83 upstream.
The Elgato Cam Link 4K HDMI video capture card reports to support three different pixel formats, where the first format depends on the connected HDMI device.
$ v4l2-ctl -d /dev/video0 --list-formats-ext ioctl: VIDIOC_ENUM_FMT Type: Video Capture [0]: 'NV12' (Y/CbCr 4:2:0) Size: Discrete 3840x2160 Interval: Discrete 0.033s (29.970 fps) [1]: 'NV12' (Y/CbCr 4:2:0) Size: Discrete 3840x2160 Interval: Discrete 0.033s (29.970 fps) [2]: 'YU12' (Planar YUV 4:2:0) Size: Discrete 3840x2160 Interval: Discrete 0.033s (29.970 fps)Changing the pixel format to anything besides the first pixel format does not work:
$ v4l2-ctl -d /dev/video0 --try-fmt-video pixelformat=YU12 Format Video Capture: Width/Height : 3840/2160 Pixel Format : 'NV12' (Y/CbCr 4:2:0) Field : None Bytes per Line : 3840 Size Image : 12441600 Colorspace : sRGB Transfer Function : Rec. 709 YCbCr/HSV Encoding: Rec. 709 Quantization : Default (maps to Limited Range) Flags :User space applications like VLC might show an error message on the terminal in that case:
libv4l2: error set_fmt gave us a different result than try_fmt!Depending on the error handling of the user space applications, they might display a distorted video, because they use the wrong pixel format for decoding the stream.
The Elgato Cam Link 4K responds to the USB video probe VS_PROBE_CONTROL/VS_COMMIT_CONTROL with a malformed data structure: The second byte contains bFormatIndex (instead of being the second byte of bmHint). The first byte is always zero. The third byte is always 1.
The firmware bug was reported to Elgato on 2020-12-01 and it was forwarded by the support team to the developers as feature request. There is no firmware update available since then. The latest firmware for Elgato Cam Link 4K as of 2021-03-23 has MCU 20.02.19 and FPGA 67.
Therefore correct the malformed data structure for this device. The change was successfully tested with VLC, OBS, and Chromium using different pixel formats (YUYV, NV12, YU12), resolutions (3840x2160, 1920x1080), and frame rates (29.970 and 59.940 fps).
Cc: stable@vger.kernel.org Signed-off-by: Benjamin Drung bdrung@posteo.de Signed-off-by: Laurent Pinchart laurent.pinchart@ideasonboard.com Signed-off-by: Mauro Carvalho Chehab mchehab+huawei@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
drivers/media/usb/uvc/uvc_video.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+)
--- a/drivers/media/usb/uvc/uvc_video.c +++ b/drivers/media/usb/uvc/uvc_video.c @@ -124,10 +124,37 @@ int uvc_query_ctrl(struct uvc_device *de static void uvc_fixup_video_ctrl(struct uvc_streaming *stream, struct uvc_streaming_control *ctrl) {
- static const struct usb_device_id elgato_cam_link_4k = {
USB_DEVICE(0x0fd9, 0x0066)- }; struct uvc_format *format = NULL; struct uvc_frame *frame = NULL; unsigned int i;
- /*
* The response of the Elgato Cam Link 4K is incorrect: The second byte* contains bFormatIndex (instead of being the second byte of bmHint).* The first byte is always zero. The third byte is always 1.** The UVC 1.5 class specification defines the first five bits in the* bmHint bitfield. The remaining bits are reserved and should be zero.* Therefore a valid bmHint will be less than 32.** Latest Elgato Cam Link 4K firmware as of 2021-03-23 needs this fix.* MCU: 20.02.19, FPGA: 67*/- if (usb_match_one_id(stream->dev->intf, &elgato_cam_link_4k) &&
ctrl->bmHint > 255) {u8 corrected_format_index = ctrl->bmHint >> 8;/* uvc_dbg(stream->dev, VIDEO,Instead of commenting out the debug log, this line needs to be replaced by:
uvc_trace(UVC_TRACE_VIDEO,
"Correct USB video probe response from {bmHint: 0x%04x, bFormatIndex: %u} to {bmHint: 0x%04x, bFormatIndex: %u}\n",ctrl->bmHint, ctrl->bFormatIndex,1, corrected_format_index); */ctrl->bmHint = 1;ctrl->bFormatIndex = corrected_format_index;- }
Yes, can you send an updated version? But does it really matter?
thanks,
greg k-h