[wtallis]

How fan control is configured depends on the SuperIO chip, so it's different for eg. Fintek SuperIOs than for Winbond/Nuvoton SuperIOs.

On Linux, a supported SuperIO will be exposed as a directory under /sys/class/hwmon. On one of my systems, the SuperIO is a Nuvoton NCT6791, so the relevant driver documentation is https://www.kernel.org/doc/Documentation/hwmon/nct6775

Relevant sysfs files to note are pwm[1-7]_mode to toggle between DC voltage and PWM control, and pwm[1-7]_enable to switch between full speed, pure software speed control, and several Nuvoton-specific automatic speed control modes.