Have a look at
Documentation/sound/hd-audio/notes.rst in the Linux kernel source. You can write to
reconfig to trigger reconfiguration, but the driver will reset, so I'm not sure if it's a good way to do that...
Alternatively, you could try to configure the codec to playback and record on the same pin at the same time (if this is what you want). But this may need tricking the ALSA driver into thinking that it's really doing playback and recording to/from different pins, and then changing the codec configuration with
hda-verb without the driver noticing. Not easy, but worth a try.
I'm not sure what you are going to try to do (use the headphone speakers as microphone?), and I don't think I want to test that on my hardware. :-)