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* Re: Patch "media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K" has been added to the 5.10-stable tree
       [not found] <162636023254123@kroah.com>
@ 2021-07-15 18:00 ` Benjamin Drung
  2021-07-15 18:18   ` Greg KH
  0 siblings, 1 reply; 5+ messages in thread
From: Benjamin Drung @ 2021-07-15 18:00 UTC (permalink / raw)
  To: gregkh, laurent.pinchart, mchehab+huawei; +Cc: stable

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 4K
> 
> to the 5.10-stable tree which can be found at:
>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> 
> 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;
> +	}
> +
>  	for (i = 0; i < stream->nformats; ++i) {
>  		if (stream->format[i].index == ctrl->bFormatIndex) {
>  			format = &stream->format[i];
> 
> 
> Patches currently in stable-queue which might be from bdrung@posteo.de are
> 
> queue-5.10/media-uvcvideo-fix-pixel-format-change-for-elgato-cam-link-4k.patch



^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: Patch "media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K" has been added to the 5.10-stable tree
  2021-07-15 18:00 ` Patch "media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K" has been added to the 5.10-stable tree Benjamin Drung
@ 2021-07-15 18:18   ` Greg KH
  2021-07-15 20:32     ` [PATCH] media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K Benjamin Drung
  0 siblings, 1 reply; 5+ messages in thread
From: Greg KH @ 2021-07-15 18:18 UTC (permalink / raw)
  To: Benjamin Drung; +Cc: laurent.pinchart, mchehab+huawei, stable

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 4K
> > 
> > to the 5.10-stable tree which can be found at:
> >     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> > 
> > 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

^ permalink raw reply	[flat|nested] 5+ messages in thread
* [PATCH] media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K
  2021-07-15 18:18   ` Greg KH
@ 2021-07-15 20:32     ` Benjamin Drung
  0 siblings, 0 replies; 5+ messages in thread
From: Benjamin Drung @ 2021-07-15 20:32 UTC (permalink / raw)
  To: Greg KH; +Cc: Laurent Pinchart, Mauro Carvalho Chehab, stable, Benjamin Drung

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>
(backported from commit 4c6e0976295add7f0ed94d276c04a3d6f1ea8f83 upstream)
Signed-off-by: Benjamin Drung <bdrung@posteo.de>
---
 drivers/media/usb/uvc/uvc_video.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

The debug message does't matter much, but I am a perfectionist.

This patch is for kernel <= 5.11.

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index a6a441d92b94..70b0d0f8026b 100644
--- 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 *dev, u8 query, u8 unit,
 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_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;
+	}
+
 	for (i = 0; i < stream->nformats; ++i) {
 		if (stream->format[i].index == ctrl->bFormatIndex) {
 			format = &stream->format[i];
-- 
2.30.2


^ permalink raw reply related	[flat|nested] 5+ messages in thread
* Re: [PATCH] media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K
  2021-03-25 21:34 Benjamin Drung
@ 2021-03-26  7:08 ` Greg KH
  0 siblings, 0 replies; 5+ messages in thread
From: Greg KH @ 2021-03-26  7:08 UTC (permalink / raw)
  To: Benjamin Drung
  Cc: Laurent Pinchart, Mauro Carvalho Chehab, linux-media,
	linux-kernel, stable, Adam Goode

On Thu, Mar 25, 2021 at 10:34:59PM +0100, Benjamin Drung wrote:
> 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 add a quirk to correct the malformed data structure.
> 
> The quirk 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).
> 
> Signed-off-by: Benjamin Drung <bdrung@posteo.de>
> ---
> 

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>

^ permalink raw reply	[flat|nested] 5+ messages in thread
* [PATCH] media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K
@ 2021-03-25 21:34 Benjamin Drung
  2021-03-26  7:08 ` Greg KH
  0 siblings, 1 reply; 5+ messages in thread
From: Benjamin Drung @ 2021-03-25 21:34 UTC (permalink / raw)
  To: Laurent Pinchart, Mauro Carvalho Chehab, linux-media, linux-kernel
  Cc: stable, Adam Goode, Benjamin Drung

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 add a quirk to correct the malformed data structure.

The quirk 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).

Signed-off-by: Benjamin Drung <bdrung@posteo.de>
---

Feel free to propose a better name for the quirk than
UVC_QUIRK_FIX_FORMAT_INDEX.

To backport to version 5.11 and earlier, the line

```
uvc_dbg(stream->dev, CONTROL,
```

needs to be changed back to

```
uvc_trace(UVC_TRACE_CONTROL,
```

 drivers/media/usb/uvc/uvc_driver.c | 13 +++++++++++++
 drivers/media/usb/uvc/uvc_video.c  | 17 +++++++++++++++++
 drivers/media/usb/uvc/uvcvideo.h   |  1 +
 3 files changed, 31 insertions(+)

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index 30ef2a3110f7..4f245b3f8bd9 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -3132,6 +3132,19 @@ static const struct usb_device_id uvc_ids[] = {
 	  .bInterfaceSubClass	= 1,
 	  .bInterfaceProtocol	= 0,
 	  .driver_info		= UVC_INFO_META(V4L2_META_FMT_D4XX) },
+	/*
+	 * Elgato Cam Link 4K
+	 * Latest firmware as of 2021-03-23 needs this quirk.
+	 * MCU: 20.02.19, FPGA: 67
+	 */
+	{ .match_flags		= USB_DEVICE_ID_MATCH_DEVICE
+				| USB_DEVICE_ID_MATCH_INT_INFO,
+	  .idVendor		= 0x0fd9,
+	  .idProduct		= 0x0066,
+	  .bInterfaceClass	= USB_CLASS_VIDEO,
+	  .bInterfaceSubClass	= 1,
+	  .bInterfaceProtocol	= 0,
+	  .driver_info		= UVC_INFO_QUIRK(UVC_QUIRK_FIX_FORMAT_INDEX) },
 	/* Generic USB Video Class */
 	{ USB_INTERFACE_INFO(USB_CLASS_VIDEO, 1, UVC_PC_PROTOCOL_UNDEFINED) },
 	{ USB_INTERFACE_INFO(USB_CLASS_VIDEO, 1, UVC_PC_PROTOCOL_15) },
diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index f2f565281e63..e348e1794d93 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -128,6 +128,23 @@ static void uvc_fixup_video_ctrl(struct uvc_streaming *stream,
 	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.
+	 */
+	if (stream->dev->quirks & UVC_QUIRK_FIX_FORMAT_INDEX && ctrl->bmHint > 255) {
+		__u8 corrected_format_index;
+
+		corrected_format_index = ctrl->bmHint >> 8;
+		uvc_dbg(stream->dev, CONTROL,
+			"Correct USB video probe response from {bmHint: 0x%04x, bFormatIndex: 0x%02x} to {bmHint: 0x%04x, bFormatIndex: 0x%02x}.\n",
+			ctrl->bmHint, ctrl->bFormatIndex,
+			ctrl->bFormatIndex, corrected_format_index);
+		ctrl->bmHint = ctrl->bFormatIndex;
+		ctrl->bFormatIndex = corrected_format_index;
+	}
+
 	for (i = 0; i < stream->nformats; ++i) {
 		if (stream->format[i].index == ctrl->bFormatIndex) {
 			format = &stream->format[i];
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index 97df5ecd66c9..bf401d5ba27d 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -209,6 +209,7 @@
 #define UVC_QUIRK_RESTORE_CTRLS_ON_INIT	0x00000400
 #define UVC_QUIRK_FORCE_Y8		0x00000800
 #define UVC_QUIRK_FORCE_BPP		0x00001000
+#define UVC_QUIRK_FIX_FORMAT_INDEX	0x00002000
 
 /* Format flags */
 #define UVC_FMT_FLAG_COMPRESSED		0x00000001
-- 
2.27.0


^ permalink raw reply related	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2021-07-15 20:33 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
     [not found] <162636023254123@kroah.com>
2021-07-15 18:00 ` Patch "media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K" has been added to the 5.10-stable tree Benjamin Drung
2021-07-15 18:18   ` Greg KH
2021-07-15 20:32     ` [PATCH] media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K Benjamin Drung
2021-03-25 21:34 Benjamin Drung
2021-03-26  7:08 ` Greg KH

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