hal_device_property_get_double
hal_device_property_get_double (device2, key))
to_device, to, hal_device_property_get_double (from_device, from));
double hal_device_property_get_double (HalDevice *device,
*result = (dbus_int64_t) ceil (hal_device_property_get_double (d, key) - atof (right_side));