IMASK
IMASK(IPL_SOFTCLOCK) |= 1 << SIR_CLOCK;
IMASK(IPL_SOFTNET) |= 1 << SIR_NET;
IMASK(IPL_SOFTTTY) |= 1 << SIR_TTY;
irqs = IMASK(IPL_HIGH);
irqs |= IMASK(q->ih_level);
if (irqs != IMASK(maxlevel))
maxlevel, irqs, IMASK(maxlevel));
imaxlevel[irq], intrmask[irq], IMASK(imaxlevel[irq]));