tcds_intrnull
/*static*/ int tcds_intrnull(void *);
slotc->sc_intrhand = tcds_intrnull;
if (sc->sc_slots[slot].sc_intrhand != tcds_intrnull)
if (sc->sc_slots[slot].sc_intrhand == tcds_intrnull)
sc->sc_slots[slot].sc_intrhand = tcds_intrnull;