ioasic_intrnull
ioasicintrs[i].iai_func = ioasic_intrnull;
if (ioasicintrs[dev].iai_func != ioasic_intrnull)
if (ioasicintrs[dev].iai_func == ioasic_intrnull)
ioasicintrs[dev].iai_func = ioasic_intrnull;
int ioasic_intrnull(void *);