Here's my research so far. Let's all give this some effort and get it sorted out.

After installing taruga's ad1986 patch I modified the plist files for AppleHDA.kext and AppleHDAController.kext to match our ad1984 by changing string 299112838 to 299112836. According to ioreg, AppleHDAController and IOHDACodecDevice load fine. The problem is now with IOHDACodecDriver.

I've noticed a clever solution at http://forum.insanelymac.com/index.php?showtopic=61513 for a different chip. This guy was stuck at exactly the same point and managed to resolve it. I think we can adapt his method to get our sound working.

It seems the next step involves modifying the Info.plist for ALCinject.kext. The layout-id field needs to be changed. It's important to modify the field with a property list editor, as a standard text editor doesn't display it right. Tarugas AD1986 patch has the field set to 13 or 0D000000 in hex. Based on the work of macdanger it seems we just need to try many values sequentially until one loads the driver. After we load the driver successfully then we can move on to fixing the codec.

The datasheet for our AD1984 can be found at: http://www.analog.com/UploadedFiles/Data_Sheets/AD1984.pdf
The linux codec dump is attached.

Post your thoughts and results here. We can do it!

Jacob