Public bug reported:
It looks like there is a function parameter mismatch when dkms tries to
build the v4l2 loopback module:
when doing an update, the dkms build runs into the following error:
DKMS make.log for v4l2loopback-0.12.7 for kernel 7.0.0-28-generic (x86_64)
Mi 22 Jul 2026 08:39:32 CEST
Building v4l2-loopback driver...
make -C /lib/modules/7.0.0-28-generic/build
M=/var/lib/dkms/v4l2loopback/0.12.7/build modules
make[1]: Verzeichnis „/usr/src/linux-headers-7.0.0-28-generic“ wird betreten
make[2]: Verzeichnis „/var/lib/dkms/v4l2loopback/0.12.7/build“ wird betreten
warning: the compiler differs from the one used to build the kernel
The kernel was built by: x86_64-linux-gnu-gcc-13 (Ubuntu
13.3.0-6ubuntu2~24.04.1) 13.3.0
You are using: gcc-13 (Ubuntu 13.3.0-6ubuntu2~24.04.1) 13.3.0
warning: pahole version differs from the one used to build the kernel
The kernel was built with: 125
You are using: 0
CC [M] v4l2loopback.o
v4l2loopback.c: In function ‘v4l2_loopback_open’:
v4l2loopback.c:2089:9: error: too few arguments to function ‘v4l2_fh_add’
2089 | v4l2_fh_add(&opener->fh);
| ^~~~~~~~~~~
In file included from
/usr/src/linux-headers-7.0.0-28-generic/include/media/v4l2-subdev.h:17,
from
/usr/src/linux-headers-7.0.0-28-generic/include/media/v4l2-device.h:13,
from v4l2loopback.c:31:
/usr/src/linux-headers-7.0.0-28-generic/include/media/v4l2-fh.h:97:6: note:
declared here
97 | void v4l2_fh_add(struct v4l2_fh *fh, struct file *filp);
| ^~~~~~~~~~~
v4l2loopback.c: In function ‘v4l2_loopback_close’:
v4l2loopback.c:2117:9: error: too few arguments to function ‘v4l2_fh_del’
2117 | v4l2_fh_del(&opener->fh);
| ^~~~~~~~~~~
/usr/src/linux-headers-7.0.0-28-generic/include/media/v4l2-fh.h:125:6: note:
declared here
125 | void v4l2_fh_del(struct v4l2_fh *fh, struct file *filp);
| ^~~~~~~~~~~
make[4]: ***
[/usr/src/linux-headers-7.0.0-28-generic/scripts/Makefile.build:289:
v4l2loopback.o] Fehler 1
make[3]: *** [/usr/src/linux-headers-7.0.0-28-generic/Makefile:2115: .] Fehler 2
make[2]: *** [/usr/src/linux-headers-7.0.0-28-generic/Makefile:248: __sub-make]
Fehler 2
make[2]: Verzeichnis „/var/lib/dkms/v4l2loopback/0.12.7/build“ wird verlassen
make[1]: *** [Makefile:248: __sub-make] Fehler 2
make[1]: Verzeichnis „/usr/src/linux-headers-7.0.0-28-generic“ wird verlassen
make: *** [Makefile:43: v4l2loopback.ko] Fehler 2
os-release:
PRETTY_NAME="Ubuntu 24.04.4 LTS"
NAME="Ubuntu"
VERSION_ID="24.04"
VERSION="24.04.4 LTS (Noble Numbat)"
VERSION_CODENAME=noble
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/";
SUPPORT_URL="https://help.ubuntu.com/";
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/";
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy";
UBUNTU_CODENAME=noble
LOGO=ubuntu-logo
** Affects: v4l2loopback (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2161489
Title:
V4L2 loopback dkms fails (7.0.0-28-generic, 0.12.7)
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