BMAC_BUFLEN
sc->sc_txbuf = malloc(BMAC_BUFLEN * BMAC_TXBUFS, M_DEVBUF, M_WAITOK);
sc->sc_rxbuf = malloc(BMAC_BUFLEN * BMAC_RXBUFS, M_DEVBUF, M_WAITOK);
DBDMA_BUILD(cmd, DBDMA_CMD_IN_LAST, 0, BMAC_BUFLEN,
vtophys((vaddr_t)sc->sc_rxbuf + BMAC_BUFLEN * i),
data = (char *)sc->sc_rxbuf + BMAC_BUFLEN * i;