Different hwmon required

[Gnarflord]

I'm running fancontrol-gui via the snap package manager and thus need udev rules. The default udev rules from this github assume hwmon7 to be the correct one for PWM control:

SUBSYSTEM=="hwmon", KERNEL=="hwmon7", RUN+="/bin/sh -c '/bin/chmod a+w /sys%p/pwm*'"

My system doesn't even have a folder for hwmon7:

❯ ls /sys/class/hwmon
hwmon0	hwmon1	hwmon2	hwmon3	hwmon4

So I looked into the directories and hwmon1 had 1 PWM controllers and hwmon4 had 7 PWM controllers. These are the controllers from my graphics card (nvidia, so noveau driver) and my motherboard:

❯ /usr/bin/cat /sys/class/hwmon/hwmon1/name
nouveau

❯ /usr/bin/cat /sys/class/hwmon/hwmon4/name
nct6798

Only after adding a line for hwmon1 and hwmon4 in the udev file was I able to control my fans.

I propose two solutions:

• Add all possible hwmon devices to the udev file

or

• Run a script to detect which hwmon has PWM controllers and only add those to the udev file

Please note that hwmon numbers will also change upon changing hardware configuration. So after swapping out a graphics card or the motherboard all numbers will be mixed up again (which will also mess with the fancontrol config file...)