ppbus_add_handler
error = ppbus_add_handler(ppbus, lp_intr, dev);
return bus->ppbus_add_handler(device_parent(dev), func, arg);
int ppbus_add_handler(device_t, void (*)(void *), void *);
ppbus->ppbus_add_handler = sc_link->parport_add_handler;
PARPORT_ADD_HANDLER_T ppbus_add_handler;
res = ppbus_add_handler(sc->ppbus, ppsintr, sc);