Node 0x1b [Volume Knob Widget] wcaps 0x600080: Mono Volume-Knob: delta=0, steps=64, direct=0, val=48 Unsolicited: tag=00, enabled=0 Connection: 0 should be responsible for the jack detection. I have noticed in my testing that the "val" is sometimes 48 and sometimes 49, but I haven't been able to correlate this with presence of headphones or otherwise.