I've looked at the new AppleHDA extension from 10.5.2 update and that's what i found:
- layouts and path maps are not anymore located in AppleHDA.kext\Contents\Info.plist - they can be found in new plugin - AppleHDAPlatformDriver.kext
- AppleHDAController.kext is matching devices by IOPCIClassMatch, but there is also an additional protection, which checks IORegistry entry of audio device - its name must begin with HDEF not AZAL or something else
I will add more information if i find something interesting.
Device name protection can be bypassed by patching the extension. (I don't know whether i can put here the patched version) Also this version in my opinion gives slightly better sound quality and on my ALC889A, especially with iTunes' sound processing enabled.
As Taruga has found some time ago, 10.5.2 extension supports some new codecs. Refer to that post: http://forum.insanelymac.com/index.php?showtopic=77191
At the moment i'm working on universal patch for AZAL* and HDEF* (my current patch only works with AZAL codecs).
(EXPERIMENTAL) Universal patched version (on AZAL* codecs it throws some assertions, but it shouldn't matter). Extension contains layout and path maps for ALC889A:
This kext is not for normal/usual use. It's experimental and should be used for making support for these new codecs only. Maybe in future it will be as functional as previous kexts patched with Taruga's patcher, but not now.