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Filename Latest commit message Latest commit date
Benjamin Drung f176dec999 media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K
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>
2021-07-19 08:53:18 +02:00
arch MIPS: fix "mipsel-linux-ld: decompress.c:undefined reference to `memmove'" 2021-07-19 08:53:16 +02:00
block rq-qos: fix missed wake-ups in rq_qos_throttle try two 2021-07-19 08:53:16 +02:00
certs certs: Move load_system_certificate_list to a common function 2021-06-30 08:47:55 -04:00
crypto crypto: shash - avoid comparing pointers to exported functions under CFI 2021-07-14 16:53:13 +02:00
Documentation clocksource: Retry clock read if long delays detected 2021-07-14 16:53:18 +02:00
drivers media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K 2021-07-19 08:53:18 +02:00
fs ubifs: Fix races between xattr_{set|get} and listxattr operations 2021-07-19 08:53:16 +02:00
include media: subdev: disallow ioctl for saa6588/davinci 2021-07-19 08:53:17 +02:00
init kbuild: add CONFIG_LD_IS_LLD 2021-06-30 08:47:44 -04:00
ipc
kernel tracing: Resize tgid_map to pid_max, not PID_MAX_DEFAULT 2021-07-19 08:53:17 +02:00
lib seq_buf: Fix overflow in seq_buf_putmem_hex() 2021-07-19 08:53:16 +02:00
LICENSES
mm mm/z3fold: fix potential memory leak in z3fold_destroy_pool() 2021-07-14 16:53:47 +02:00
net sctp: add size validation when walking chunks 2021-07-19 08:53:13 +02:00
samples samples/bpf: Fix the error return code of xdp_redirect's main() 2021-07-14 16:53:30 +02:00
scripts kbuild: Fix objtool dependency for 'OBJECT_FILES_NON_STANDARD_<obj> := n' 2021-07-14 16:53:20 +02:00
security selinux: use __GFP_NOWARN with GFP_NOWAIT in the AVC 2021-07-19 08:53:10 +02:00
sound ASoC: tegra: Set driver_name=tegra for all machine drivers 2021-07-19 08:53:16 +02:00
tools perf bench: Fix 2 memory sanitizer warnings 2021-07-19 08:53:14 +02:00
usr
virt KVM: do not allow mapping valid but non-reference-counted pages 2021-06-30 08:47:50 -04:00
.clang-format
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Makefile Linux 5.4.132 2021-07-14 16:53:49 +02:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.