RL_MII
CSR_WRITE_1(sc, RL_MII, \
CSR_READ_1(sc, RL_MII) | x)
CSR_WRITE_1(sc, RL_MII, \
CSR_READ_1(sc, RL_MII) & ~x)
CSR_WRITE_2(sc, RL_MII, 0);
ack = CSR_READ_2(sc, RL_MII) & RL_MII_DATAIN;
if (CSR_READ_2(sc, RL_MII) & RL_MII_DATAIN)