MESON_RBUFSZ
u_char sc_rbuf[MESON_RBUFSZ]; /* good enough for sizeof RXFIFO */
if ((sc->sc_rbuf_w - sc->sc_rbuf_r) >= (MESON_RBUFSZ - 1))
sc->sc_rbuf[sc->sc_rbuf_w++ & (MESON_RBUFSZ - 1)] = c;
c = sc->sc_rbuf[sc->sc_rbuf_r++ & (MESON_RBUFSZ - 1)];