I have added a note about the mainline emc2305 driver to the manual.
The bad news is that it automatically turns off the fans when it loads… eek!
I think this is because it uses a different method (PWM % rather than RPM, which is what we have always used), anyway, I will try and submit a patch to fix it. The other features will take more time to upstream.
As mentioned the mainline driver only works on a PWM % level. As a guide, 50% (128) is returning roughly 3000rpm.
If anyone does need to use it, make sure you set the fan speed immediately after loading the module:
# Turn fan to full speed
$ echo 255 > /sys/class/hwmon/hwmon4/pwm1
$ cat /sys/class/hwmon/hwmon4/fan1_input
5228
# Turn fan to "half" speed (~3000 RPM)
$ echo 128 > /sys/class/hwmon/hwmon4/pwm1
$ cat /sys/class/hwmon/hwmon4/fan1_input
3062