Service initialization failed with `Unable to open a file descriptor for /dev/video2`

This guide worked perfectly, so thank you!

I have one issue left, though: on boot, the service fails to start with the message Unable to open a file descriptor for /dev/video2. I guess this is due to enable-ir-emitter.service starting before the webcam is properly detected by the system. I am unsure how to keep the service from starting, until the webcam is detected, as my technical knowledge of systemd is fairly limited. I tried adding after=systemd-udev-settle.service, but this did not solve the issue. Interestingly, the IR-Blaster sometimes still works fine after a reboot when logging in in sddm, but not reliably.

[m4rtins]

One additional Note: the IR-Blaster also did not work upon resume from hibernate, as the service was applied during hibernation, but not on resume. Adding the corresponding services to After fixed this.

[m4rtins]

I am using Manjaro and according to this, the usage of udev-settle is not recommended anyway. I have tried to use udev-rules in the meantime following the first answer in this question. It did not work as well, but adding Requires=... seems to have done the trick.

So in total, I have a file webcam.rules in /etc/udev/rules.d:

KERNEL=="video2", SYMLINK="video2", TAG+="systemd"

And enable-ir-emitter.service reads:

[Unit]
Description=enable ir emitter
Requires=dev-video2.device
After=dev-video2.device

[Service]
ExecStart=/usr/local/bin/enable-ir-emitter

[Install]
WantedBy=multi-user.target suspend.target hibernate.target hybrid-sleep.target suspend-then-hibernate.target`