DESC_OFFS
((sc)->sc_dmamap->dm_segs[0].ds_addr + DESC_OFFS((chp)->ch_index, (n)))
bus_dmamap_sync(sc->sc_dmat, sc->sc_dmamap, DESC_OFFS(ch->ch_index, 0),
desclen = DESC_OFFS(sc->sc_nchan, 0);
sc->sc_ndesc_ch = DESC_OFFS(1, 0) / sizeof(struct sun6idma_desc);
ch->ch_dmadesc = (void *)((uintptr_t)sc->sc_dmadescs + DESC_OFFS(index, 0));