Setting Audio Subsystem Registers Not Exposed by ALSA Driver

I would like to disable the high pass (DC Block) filters in the TX and RX path by setting the LPASS_CDC_TXn_MUX_CTL (0x0771C26C+0x20n n=[1…2]) and LPASS_CDC_RXnB5_CTL (0x0771C030+0x20n n=[1…3]) registers to BYPASS from NO_BYPASS. Those options are not exposed through the ALSA driver.

What is the best way to get at those registers?
I am not sure where to start looking?
I am running Linaro RPB console only.