acc_prd
struct acc_prd prdtbl[PRD_TABLE_MAX][GCSCAUDIO_NPRDTABLE];
struct acc_prd *prdp;
(sc->sc_prd.p_prdmap->dm_segs[0].ds_addr) + sizeof(struct acc_prd) * \
sizeof(struct acc_prd) * i, BUS_DMASYNC_PREWRITE);