smc_watchdog
callout_stop(&sc->smc_watchdog);
static callout_func_t smc_watchdog;
callout_init_mtx(&sc->smc_watchdog, &sc->smc_mtx, 0);
callout_drain(&sc->smc_watchdog);
callout_reset(&sc->smc_watchdog, hz * 2, smc_watchdog, sc);
callout_stop(&sc->smc_watchdog);
callout_stop(&sc->smc_watchdog);
struct callout smc_watchdog;