Messing around with FreeBSD audio

FreeBSD 

Source: man snd_hda

To enable bass/treble controls for pcm0, add the following to /boot/loader.conf:

hint.pcm.0.eq="1"

For me the front headphone jack was plumbed to pcm1. To dump all information about the current configuration, do:

sysctl dev.hdac.0.pindump=1
dmesg
hdaa0: nid   0x    as seq device       conn  jack    loc        color   misc
...
hdaa0: 20 01014410 1  0  Line-out      Jack  1/8     Rear       Green   4
hdaa0:     Caps: IN OUT HP           Sense: 0x80000000 (connected)
...
hdaa0: 27 02214c1f 2  0  Headphones    Jack  1/8     Front      Green   12
hdaa0:     Caps: IN OUT HP      VREF Sense: 0x00000000 (disconnected)

In my case the rear audio jack has node ID (nid) 20 and is set to association (as) 1 and sequence (seq) 0. As for the front headphone jack nid=27, as=2, and seq=0. Changing it to as=1 will put it in the same group as the rear jack and setting seq=15 will make sure the rear jack gets muted when using the front jack. Add to /boot/loader.conf:

hint.hdac.0.cad0.nid27.config="as=1 seq=15"