V4l2loopback fails to load

Robotics & Edge Computing Jetson & Embedded Systems Jetson AGX Orin
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1

Hi,

I’m working on a Jetson Orin AGX that has a Rogue carrier board from CTI. I’m using JetPack 5.1.2 and I’ve been having the following issue.

When I try to create a virtual v4l2 device by loading the v4l2loopback module to the kernel it always fail.
I’ve followed the instructions that are available on the following forum post: https://forums.developer.nvidia.com/t/jetpack-4-2-1-building-v4l2loopback-fails/79201/2

I’ve tried multiple methods for installing the v4l2loopback modules but whenever I try to load the module I see the following messages

ocu@ocuRR:~$ sudo modprobe v4l2loopback video_nr=20
modprobe: ERROR: could not insert 'v4l2loopback': Invalid argument

dmesg

[ 4444.367764] v4l2loopback: disagrees about version of symbol video_devdata
[ 4444.367990] v4l2loopback: Unknown symbol video_devdata (err -22)
[ 4444.368192] v4l2loopback: disagrees about version of symbol video_unregister_device
[ 4444.368419] v4l2loopback: Unknown symbol video_unregister_device (err -22)
[ 4444.368629] v4l2loopback: disagrees about version of symbol video_device_alloc
[ 4444.368836] v4l2loopback: Unknown symbol video_device_alloc (err -22)
[ 4444.369038] v4l2loopback: disagrees about version of symbol v4l2_device_register
[ 4444.369245] v4l2loopback: Unknown symbol v4l2_device_register (err -22)
[ 4444.369439] v4l2loopback: disagrees about version of symbol __video_register_device
[ 4444.369681] v4l2loopback: Unknown symbol __video_register_device (err -22)
[ 4444.369867] v4l2loopback: disagrees about version of symbol v4l2_device_unregister
[ 4444.370729] v4l2loopback: Unknown symbol v4l2_device_unregister (err -22)
[ 4444.371741] v4l2loopback: disagrees about version of symbol video_device_release
[ 4444.372861] v4l2loopback: Unknown symbol video_device_release (err -22)

And yes, videodev is also loaded and working

[    0.417314] videodev: Linux video capture interface: v2.00

Do you know what could be the issue?

On addition to that, this exact same module with the exact same building process does work on a Jetson Orin Nano. It’s not working only on the Orin AGX

4

Hi,
Please try the steps:
Gstreamer v4l2loopback hw mjpeg stream - #5 by Honey_Patouceul

5

Hi,

I was trying to follow the steps mentioned in the forum post you shared but I ran into the following errors when building v4l2loopback

root@ocuRR:/usr/src# dkms build -m v4l2loopback/0.12.5

Creating symlink /var/lib/dkms/v4l2loopback/0.12.5/source ->
                 /usr/src/v4l2loopback-0.12.5

DKMS: add completed.

Kernel preparation unnecessary for this kernel.  Skipping...

Building module:
cleaning build area...
make -j8 KERNELRELEASE=5.10.120-tegra KERNEL_DIR=/lib/modules/5.10.120-tegra/build all...(bad exit status: 2)
ERROR (dkms apport): binary package for v4l2loopback: 0.12.5 not found
Error! Bad return status for module build on kernel: 5.10.120-tegra (aarch64)
Consult /var/lib/dkms/v4l2loopback/0.12.5/build/make.log for more information.

I checked the make.log and I saw the following message

root@ocuRR:/usr/src# cat /var/lib/dkms/v4l2loopback/0.12.5/build/make.log
DKMS make.log for v4l2loopback-0.12.5 for kernel 5.10.120-tegra (aarch64)
Wed Sep 18 10:11:02 EDT 2024
Building v4l2-loopback driver...
make -C /lib/modules/5.10.120-tegra/build M=/var/lib/dkms/v4l2loopback/0.12.5/build modules
make[1]: Entering directory '/usr/src/linux-headers-5.10.120-tegra-ubuntu20.04_aarch64/kernel-5.10'

  ERROR: Kernel configuration is invalid.
         include/generated/autoconf.h or include/config/auto.conf are missing.
         Run 'make oldconfig && make prepare' on kernel src to fix it.

make[1]: *** [Makefile:750: include/config/auto.conf] Error 1
make[1]: Leaving directory '/usr/src/linux-headers-5.10.120-tegra-ubuntu20.04_aarch64/kernel-5.10'
make: *** [Makefile:43: v4l2loopback.ko] Error 2
root@ocuRR:/usr/src#

I tried executing the command mentioned in the make.log but I got the following error

root@ocuRR:/usr/src/linux-headers-5.10.120-tegra-ubuntu20.04_aarch64/kernel-5.10# make oldconfig && make prepare
drivers/video/Kconfig:27: can't open file "drivers/video/tegra/Kconfig"
make[1]: *** [scripts/kconfig/Makefile:71: oldconfig] Error 1
make: *** [Makefile:633: oldconfig] Error 2

Is this related to the content of the git repository thay I just cloned?
How can I get the “binary package for v4l2loopback”?

7

Hi,
We can successfully run the steps on Jetpack 5.1.4 and 6.2. You may upgrade and check again. Please ensure all commands are executed.

9

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