GUS_DMAOUT_ACTIVE
KASSERT((sc->sc_flags & (GUS_DMAOUT_ACTIVE | GUS_LOCKED)) == 0);
sc->sc_flags &= ~GUS_DMAOUT_ACTIVE; /* pending DMA is done */
sc->sc_flags |= GUS_DMAOUT_ACTIVE;
sc->sc_flags &= ~(GUS_DMAOUT_ACTIVE|GUS_LOCKED);