From mISDN.org

HFC-4S/8S/E1 mISDN driver

A driver for Cologne Chip AG's HFC-4S, HFC-8S and HFC-E1 ISDN controller has been developed by Andreas Eversberg (jolly) and is available within mISDN since January 2004. Just follow the 'Installing mISDN' instructions to retrieve the driver.

source description

Filename   hfc_multi.c layer1 mISDN driver hfc_multi.h register mapping, etc.