The only interface I've found for setting the fan speed with the thinkpad-acpi module, is setting pre-defined levels, 0-7. Example:
sudo su -c 'echo "level 2" > /proc/acpi/ibm/fan'
I would like to set the fan speed by RPM and not by pre-defined levels. Level 2 is 2000 RPM, and level 3 is 3500 RPM. I would like my fan to run at about 2500-3000 RPM (at a certain temperature level, of course). Does a RPM based interface exist?