v4l2loopback-dkms-0.12.1 fails to install with current raspberrypi-kernel version

[vincent-olivert-riera]

The v4l2loopback-dkms-0.12.1 package cannot be installed because the kernel module fails to compile against kernels >= 5.1.

# apt install v4l2loopback-dkms
Reading package lists... Done
Building dependency tree       
Reading state information... Done
v4l2loopback-dkms is already the newest version (0.12.1-1).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n] Y
Setting up v4l2loopback-dkms (0.12.1-1) ...
Removing old v4l2loopback-0.12.1 DKMS files...

------------------------------
Deleting module version: 0.12.1
completely from the DKMS tree.
------------------------------
Done.
Loading new v4l2loopback-0.12.1 DKMS files...
It is likely that 5.4.51-v7l+ belongs to a chroot's host
Building for 5.4.51+, 5.4.51-v7+, 5.4.51-v7l+ and 5.4.51-v8+
Building initial module for 5.4.51+
Error! Bad return status for module build on kernel: 5.4.51+ (armv7l)
Consult /var/lib/dkms/v4l2loopback/0.12.1/build/make.log for more information.
dpkg: error processing package v4l2loopback-dkms (--configure):
 installed v4l2loopback-dkms package post-installation script subprocess returned error exit status 10
Errors were encountered while processing:
 v4l2loopback-dkms
E: Sub-process /usr/bin/dpkg returned an error code (1)

It is actually caused by a warning being treated as an error:

# cat /var/lib/dkms/v4l2loopback/0.12.1/build/make.log
DKMS make.log for v4l2loopback-0.12.1 for kernel 5.4.51+ (armv7l)
Thu 23 Jul 19:00:04 BST 2020
Building v4l2-loopback driver...
make -C /lib/modules/5.4.51+/build M=/var/lib/dkms/v4l2loopback/0.12.1/build modules
make[1]: Entering directory '/usr/src/linux-headers-5.4.51+'
  CC [M]  /var/lib/dkms/v4l2loopback/0.12.1/build/v4l2loopback.o
/var/lib/dkms/v4l2loopback/0.12.1/build/v4l2loopback.c: In function ‘vidioc_qbuf’:
/var/lib/dkms/v4l2loopback/0.12.1/build/v4l2loopback.c:1509:4: error: implicit declaration of function ‘v4l2_get_timestamp’; did you mean ‘v4l2_get_subdevdata’? [-Werror=implicit-function-declaration]
    v4l2_get_timestamp(&b->buffer.timestamp);
    ^~~~~~~~~~~~~~~~~~
    v4l2_get_subdevdata
cc1: some warnings being treated as errors
make[2]: *** [scripts/Makefile.build:266: /var/lib/dkms/v4l2loopback/0.12.1/build/v4l2loopback.o] Error 1
make[1]: *** [Makefile:1709: /var/lib/dkms/v4l2loopback/0.12.1/build] Error 2
make[1]: Leaving directory '/usr/src/linux-headers-5.4.51+'
make: *** [Makefile:43: v4l2loopback.ko] Error 2

The issue has been fixed upstream: v4l2loopback/v4l2loopback@0b8feb8

Would it be possible to get this package updated?

[isolin]

My video streaming setup stopped working after updating the kernel, due to this issue :(

[nschimme]

In order to work around this:

wget http://raspbian.raspberrypi.org/raspbian/pool/main/v/v4l2loopback/v4l2loopback-dkms_0.12.5-1_all.deb
sudo apt install ./v4l2loopback-dkms_0.12.5-1_all.deb

[jlg89]

This is what I get:

$ uname -r
5.4.51-v7+

$ sudo apt install ./v4l2loopback-dkms_0.12.5-1_all.deb

<snip>
Module build for kernel 5.4.51-v7+ was skipped since the
kernel headers for this kernel does not seem to be installed.
<snip>

(install says it completed successfully)

$ sudo modprobe -r v4l2loopback
modprobe: FATAL: Module v4l2loopback not found.

[jlg89]

I had to run:

$ sudo apt full-upgrade

Reboot, then:

$ sudo apt reinstall ./v4l2loopback-dkms_0.12.5-1_all.deb

[XECDesign]

I've added the backported 5.4-compatible package to our repo. It should be live within an hour.

[surak]

Will this exist for the recent kernels and 64 bit?

[RuroWork]

sudo apt install linux-headers-$(uname -r)
wget http://ftp.us.debian.org/debian/pool/main/v/v4l2loopback/v4l2loopback-dkms_0.13.2-1_all.deb
sudo dpkg -i v4l2loopback-dkms_0.13.2-1_all.deb

[XECDesign]

sudo apt install linux-headers-$(uname -r) wget http://ftp.us.debian.org/debian/pool/main/v/v4l2loopback/v4l2loopback-dkms_0.13.2-1_all.deb sudo dpkg -i v4l2loopback-dkms_0.13.2-1_all.deb

That's definitely something people shouldn't do and won't work.

[ioaniatr]

For me, run the following solved the issue, as mentioned: here
sudo apt install --reinstall linux-headers-$(uname -r)