Loading v4l2loopback kernel module

Loading v4l2loopback kernel module

[Stefan Baums]

Dear list,

I installed the v4l2loopback-linux-module package, but the module
was not loaded. Next I added the following to my system.scm:

   (services
     (append
      (list

      ...

            (simple-service 'my-kernel-module-loader-v4l2loopback
                            kernel-module-loader-service-type
                            '("v4l2loopback"))
      ...

   )
      %desktop-services))

and reconfigured, but the module was still not loaded. Even manual

   sudo modprobe v4l2loopback

fails with

   modprobe: FATAL: Module v4l2loopback not found in directory /run/booted-system/kernel/lib/modules/5.17.1

What am I supposed to do?

All best,
Stefan

Re: Loading v4l2loopback kernel module

[Michael Rohleder]

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Hey Stefan!

Stefan Baums <baums@stefanbaums.com> writes:
> I installed the v4l2loopback-linux-module package, but the module
> was not loaded.

I use the module this way:

(operating-system
  ...
  (kernel-loadable-modules (list v4l2loopback-linux-module))
  ... )


Happy hacking!
-- 
The easiest way to get shot is to carry a gun -- Atticus Finch

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Re: Loading v4l2loopback kernel module

[Stefan Baums]

Dear Michael,

> (operating-system
>   ...
>   (kernel-loadable-modules (list v4l2loopback-linux-module))
>   ... )

thank you, that helped. For good measure, I also kept

   (simple-service 'my-kernel-module-loader-thunderbolt
                   kernel-module-loader-service-type
                   '("thunderbolt"))
   (simple-service 'my-kernel-module-loader-v4l2loopback
                   kernel-module-loader-service-type
                   '("v4l2loopback"))
   (simple-service 'my-kernel-module-loader-zram
                   kernel-module-loader-service-type
                   '("zram"))

Trying to add thunderbolt and zram to your code threw an error. I
suppose the difference is that v4l2loopback comes in its own Guix
package.

Reconfigure rebuilt the kernel then, but unfortunately in the end
failed with the below. What might be going on now?

All best,
Stefan

------------------------------------------------------------------

The following derivation will be built:
  /gnu/store/ca1iiszjxbshrv6mmdjfra89di5ggcjb-install-bootloader.scm.drv

building /gnu/store/ca1iiszjxbshrv6mmdjfra89di5ggcjb-install-bootloader.scm.drv...
guix system: bootloader successfully installed on '(/boot/efi)'
shepherd: Evaluating user expression (and (defined? (quote transient?)) (map (# ?) ?)).
Backtrace:
In guix/store.scm:
   1320:8 19 (call-with-build-handler _ _)
   1320:8 18 (call-with-build-handler _ _)
   1320:8 17 (call-with-build-handler #<procedure 7fe892daa1b0 at g…> …)
  2129:25 16 (run-with-store #<store-connection 256.99 7fe894270b40> …)
In ice-9/boot-9.scm:
  1747:15 15 (with-exception-handler #<procedure 7fe8929a3bd0 at ic…> …)
In ice-9/exceptions.scm:
   406:15 14 (_)
In ice-9/boot-9.scm:
  1752:10 13 (with-exception-handler _ _ #:unwind? _ # _)
In guix/scripts/system.scm:
   870:15 12 (_)
In guix/store.scm:
  2129:25 11 (run-with-store #<store-connection 256.99 7fe88fb07c30> …)
In guix/scripts/system.scm:
   870:15 10 (_ _)
In guix/scripts/system/reconfigure.scm:
    145:2  9 (_ _)
In guix/scripts/system.scm:
   768:14  8 (_ _)
In ice-9/boot-9.scm:
   222:17  7 (map1 (#<<live-service> provision: (term-tty1) requi…> …))
In ice-9/eval.scm:
   173:55  6 (_ #(#(#<directory (guile-user) 7fe8aa191c80>) #<<liv…>))
   182:19  5 (proc #(#(#<directory (guile-user) 7fe8aa191c80>) #<<…>))
   142:16  4 (compile-top-call #<directory (guile-user) 7fe8aa191c80> …)
In unknown file:
           3 (%resolve-variable (7 . live-service-transient) #<direc…>)
In ice-9/boot-9.scm:
  1685:16  2 (raise-exception _ #:continuable? _)
  1683:16  1 (raise-exception _ #:continuable? _)
  1685:16  0 (raise-exception _ #:continuable? _)

ice-9/boot-9.scm:1685:16: In procedure raise-exception:
error: live-service-transient: unbound variable

------------------------------------------------------------------

Re: Loading v4l2loopback kernel module

[Michael Rohleder]

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Hey Stefan!

Stefan Baums <baums@stefanbaums.com> writes:
> Reconfigure rebuilt the kernel then, but unfortunately in the end
> failed with the below. What might be going on now?

This is https://issues.guix.gnu.org/54833
Should be fixed with 7da907f90e.  Please try again ;)

Happy hacking!
-- 
"Whoa...I did a 'zcat /vmlinuz > /dev/audio' and I think I heard God..."
(mikecd on #Linux)

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Re: Loading v4l2loopback kernel module

[Stefan Baums]

> Should be fixed with 7da907f90e.

Excellent. Reconfigure worked now, and after reboot all three
modules are loaded. Thank you!