bus_child_present
sc->sc_invalid = !bus_child_present(dev);
sc->sc_invalid = !bus_child_present(dev);
siba->siba_invalid = !bus_child_present(dev);
sc->sc_invalid = !bus_child_present(dev);
sc->wi_gone |= !bus_child_present(dev);
DEVMETHOD(bus_child_present, cbb_child_present),
DEVMETHOD(bus_child_present, cbb_child_present),
KOBJMETHOD(bus_child_present, root_child_present),
int bus_child_present(device_t child);