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Benjamin Drung 691e71cf1f media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K 
commit 4c6e097629 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>
History 2021-07-19 10:04:54 +02:00
arch arm64: tlb: fix the TTL value of tlb_get_level 2021-07-19 10:04:50 +02:00
block rq-qos: fix missed wake-ups in rq_qos_throttle try two 2021-07-19 10:04:52 +02:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto crypto: sm2 - fix a memory leak in sm2 2021-07-14 17:06:44 +02:00
Documentation docs: Makefile: Use CONFIG_SHELL not SHELL 2021-07-19 10:04:50 +02:00
drivers media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K 2021-07-19 10:04:54 +02:00
fs ubifs: Fix races between xattr_{set|get} and listxattr operations 2021-07-19 10:04:51 +02:00
include media: subdev: disallow ioctl for saa6588/davinci 2021-07-19 10:04:53 +02:00
init sched/core: Initialize the idle task with preemption disabled 2021-07-14 17:06:21 +02:00
ipc ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry 2021-05-22 15:09:07 -10:00
kernel tracing: Resize tgid_map to pid_max, not PID_MAX_DEFAULT 2021-07-19 10:04:52 +02:00
lib seq_buf: Fix overflow in seq_buf_putmem_hex() 2021-07-19 10:04:52 +02:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm mm/mremap: hold the rmap lock in write mode when moving page table entries. 2021-07-19 10:04:47 +02:00
net sctp: add size validation when walking chunks 2021-07-19 10:04:46 +02:00
samples samples/bpf: Fix the error return code of xdp_redirect's main() 2021-07-14 17:07:08 +02:00
scripts kbuild: Fix objtool dependency for 'OBJECT_FILES_NON_STANDARD_<obj> := n' 2021-07-14 17:06:40 +02:00
security selinux: use __GFP_NOWARN with GFP_NOWAIT in the AVC 2021-07-19 10:04:38 +02:00
sound ASoC: tegra: Set driver_name=tegra for all machine drivers 2021-07-19 10:04:51 +02:00
tools selftests/lkdtm: Fix expected text for CR4 pinning 2021-07-19 10:04:52 +02:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt KVM: do not allow mapping valid but non-reference-counted pages 2021-06-24 11:55:11 -04:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Marek's other e-mail address and identity without diacritics 2021-06-24 19:40:54 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge branch 'akpm' (patches from Andrew) 2021-06-25 11:05:03 -07:00
Makefile Linux 5.13.2 2021-07-14 17:07:52 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.