AHC_DMA_LAST_SEG
sg->len = ahc_htole32(len | AHC_DMA_LAST_SEG);
while ((ahc_le32toh(sg->len) & AHC_DMA_LAST_SEG) == 0) {
sg->len |= ahc_htole32(AHC_DMA_LAST_SEG);