rng_ctl_data_t
n2rng->n_ctl_data = kmem_alloc(sizeof (rng_ctl_data_t), KM_SLEEP);
kmem_free(n2rng->n_ctl_data, sizeof (rng_ctl_data_t));
rng_ctl_data_t *n_ctl_data; /* Only valid in ctl domain */