RFD_PKT_OFFSET
PUTRFD16(rfd, RFD_SIZ_OFFSET, RFD_SIZE - RFD_PKT_OFFSET);
SYNCRFD(rfd, 0, RFD_PKT_OFFSET, DDI_DMA_SYNC_FORDEV);
bcopy(rfd->vaddr + RFD_PKT_OFFSET, mp->b_wptr, cnt);