apple_smc_read_key
int apple_smc_read_key(struct apple_smc_softc *, uint32_t, void *, size_t);
return apple_smc_read_key(smc, key, p, 1);
error = apple_smc_read_key(smc, key, &be, 2);
error = apple_smc_read_key(smc, key, &be, 4);
int apple_smc_read_key(struct apple_smc_tag *,
error = apple_smc_read_key(sc->sc_smc, fan_desc_key, &fan_desc,