ASC_MAXXFERSIZE
error = bus_dmamap_create(asc->sc_dmat, ASC_MAXXFERSIZE, 1,
ASC_MAXXFERSIZE, 0, BUS_DMA_NOWAIT, &asc->sc_dmamap);
*dmasize = asc->sc_dmasize = uimin(*dmasize, ASC_MAXXFERSIZE);