There is no generic driver for ALC889, you should look for something specific to your mobo/computer/laptop model, as different hardware with the same codec may be different (different adresses, inputs/outputs, paths, etc.).
Having said that, tmongkol's thread on insanelymac have one of the most complete ALC885/9 patched AppleHDA kexts that I could find, if you have a Gigabyte motherboard that would be your best bet.
Alternatively you can always use VoodooHDA.