dkms broken for linux>=5.18

[AlexTMjugador]

Description

I've just updated my Debian unstable system to the latest kernel and v4l2loopback-dkms versions, and to my unpleasant surprise I was greeted with the fact that the v4l2loopback module now fails to build because the dkms.conf configuration thinks that my kernel is missing the needed V4L2 configuration options:

Needless to say, this makes the v42loopback module not build at all. I've looked at the /lib/modules/5.18.0-3-amd64/build/.config file and confirmed that CONFIG_VIDEO_V4L2 is not explicitly mentioned, but other V4L2-related configurations were enabled, which I think that transitively imply CONFIG_VIDEO_V4L2 anyway. It's worth mentioning that everything worked fine on a previous v4l2loopback-dkms version with the 5.18.0-2 kernel, and I doubt that Debian really stopped enabling the necessary kernel features in such a small version bump.

As a temporary fix, I've removed the troublesome check from the dkms.conf file, and everything worked fine for me, as before.

If this issue does not get resolved somehow, I expect v4l2loopback-dkms to eventually be broken in other less unstable environments, too, including Ubuntu.

Steps to reproduce

1. Install the v4l2loopback-dkms package on an updated Debian unstable system
2. Watch how it refuses to build due to dkms.conf settings

Expected results

It should just work.

Environment

• v4l2loopback version: 0.12.7

• kernel version: Linux hostname 5.18.0-3-amd64 #1 SMP PREEMPT_DYNAMIC Debian 5.18.14-1 (2022-07-23) x86_64 GNU/Linux

• Distribution (+version):

No LSB modules are available.
Distributor ID: Debian
Description:    Debian GNU/Linux bookworm/sid
Release:        unstable
Codename:       sid

[umlaeute]

this is actually an issue with the Debian package (so you should have reported it there..)

i'll take a look.

[umlaeute]

the issue seems to be that with 5.18, the kernel config variables for enabling v4l2 has been renamed from CONFIG_VIDEO_V4L2 to CONFIG_VIDEO_DEV).

Go figure.

[AlexTMjugador]

Thank you for looking into this. Would you like receiving a PR to also check for CONFIG_VIDEO_DEV? 😄

this is actually an issue with the Debian package (so you should have reported it there..)

I've thought about that, but the Debian package didn't patch the dkms.conf file with the check, so I figured out that the problem was present upstream and that some paperwork could be saved by reporting the issue here directly.