ad_detach
int (*ad_detach)(device_t dev);
error = sc->sc_ad->ad_detach(dev);
DEVMETHOD(device_detach, ad_detach),
int (*ad_detach)(device_t dev);
.ad_detach = sili_pci_detach,
.ad_detach = sili_pci_detach,
error = sc->sc_ad->ad_detach(dev);