device_set_devclass
if (device_set_devclass(child,
(void)device_set_devclass(child, NULL);
result = device_set_devclass(child, best->driver->name);
(void)device_set_devclass(child, NULL);
error = device_set_devclass(dev, classname);
int device_set_devclass(device_t dev, const char *classname);