Copied from https://gitlab.com/ddcci-driver-linux/ddcci-driver-linux/-/issues/7#note_151296583
With nvidia drivers, ddcci-driver-linux does not automatically create a backlight device.
A device can be created manually by doing:
$ echo 'ddcci 0x37' | sudo tee /sys/bus/i2c/devices/i2c-<number>/new_device
where is given by
$ ddcutil detect
This fix does this automatically when the i2c device is added.