Comment 26 for bug 994685

I think that the problem might be that node 0x02 of the codec has a volume control labeled "Speaker playback volume", and the headphone path goes through that node for output. When headphones are plugged in, PulseAudio turns "Speaker playback volume" off, which mutes the headphones.

If the theory is correct, the offending/fixing patch messes around with volume control names so that "Speaker playback volume" will be named something else.