I have an Intel DG965WH board, with onboard sound, which works with the snd-hda-intel driver. The rear headphone jack works fine. My case has front panel headphone and microphone jacks, which I've hooked up using the audio connections on the board. However, in 2.6.30, the front panel headphone jack does not work. In previous versions (at least 2.6.26, though I think as late as 2.6.29), the front panel headphone jack provided audio, but plugging in headphones did not mute the audio from the rear headphone jack.
Cross-reference: originally reported to Debian as http://bugs.debian.org/451045
Does the issue still exist with 3.12 kernel? If yes, please give alsa-info.sh output.
I no longer have this system, so I have no way to test that.
OK, let's close.