sk_probe
sk = sk_probe(NULL, NULL, 0, 0);
sk = sk_probe(application, key_handle, key_handle_len, 0);
sk = sk_probe(NULL, NULL, 0, 1);
sk = sk_probe(NULL, NULL, 0, 0);
static int sk_probe(device_t);
DEVMETHOD(device_probe, sk_probe),