Error building v4l2-loopback driver on pi400

Question

I'm trying to turn my phone webcam into a "fake webcam" for my raspberry pi 400, but I get an error:

Anas@raspberrypi:~/Downloads/server/v4l2loopback $ make
Building v4l2-loopback driver...
make -C /lib/modules/`uname -r`/build M=/home/Anas/Downloads/server/v4l2loopback modules
make[1]: *** /lib/modules/5.10.17-v7l+/build: No such file or directory.  Stop.
make: *** [Makefile:46: v4l2loopback.ko] Error 2
Anas@raspberrypi:~/Downloads/server/v4l2loopback $

Please help with this.

Answer 1

You might need to build the kernel once. What do you see when you have a ls -la /lib/modules/5.10.17-v7l+/?

You might follow these instructions here, as they need the same for their camera modules: https://www.arducam.com/docs/cameras-for-raspberry-pi/pivariety/how-to-access-and-program-the-pivariety-camera-using-command-line-python-opencv-and-gstreamer/#22-create-a-virtual-video-node-access-by-python

TL;DR:

cd ~
sudo apt install git bc bison flex libssl-dev python2
sudo wget https://raw.githubusercontent.com/RPi-Distro/rpi-source/master/rpi-source -O /usr/local/bin/rpi-source && sudo chmod +x /usr/local/bin/rpi-source && /usr/local/bin/rpi-source -q --tag-update
mkdir $(uname -r)
rpi-source -d $(uname -r)

Before you configure v4l2loopback

Answer 2

I had the same issue and installing the kernel headers solved it for me

sudo apt install raspberrypi-kernel-headers