Lenovo ThinkPad T420s
The thinkpad_acpi kernel module needs to be configured so user space programs can control the fan speed.
The thinkfan configuration file also needs to know how to set the fan speed. Replace the default sensor settings with the following.
To make sound work, make sure all channels are unmuted via alsamixer or similar, and configure the snd-hda-intel module to load specifically for a thinkpad.