bus-independent core driver. Tested on all three bus types, including
an isa 3c509 masquerading as an eisa device (use ep* at eisa? slot ? in
your kernel config file to catch this one).
XXX Driver still needs to be converted to <machine/bus.h>
- split softc size and match/attach out from cfdriver into
a new struct cfattach.
- new "attach" directive for files.*. May specify the name of
the cfattach structure, so that devices may be easily attached
to parents with different autoconfiguration semantics.