$ cd /root/rig && make            # kmod.mk, SYSDIR=/usr/src/sys, real ahci.h
cc ... -D_KERNEL ... -c df2420_rig.c
cc -Wl,--build-id=sha1 -nostdlib -Wl,--hash-style=sysv -r -Wl,-d -o df2420rig.ko df2420_rig.o
make rc=0    (df2420rig.ko, 6584 bytes)