rum_bbp_read
bbp4 = rum_bbp_read(sc, 4);
bbp77 = rum_bbp_read(sc, 77);
static uint8_t rum_bbp_read(struct rum_softc *, uint8_t);
bbp3 = rum_bbp_read(sc, 3);
const uint8_t val = rum_bbp_read(sc, 0);