bestcomm_bd_status
uint32_t bestcomm_bd_status(struct bestcomm_bdring *, u_int idx);
st = bestcomm_bd_status(&sc->sc_rxring, idx);
st = bestcomm_bd_status(&sc->sc_txring, idx);
while ((bestcomm_bd_status(&sc->sc_txring, sc->sc_curblk) &