From changeset 864 on, CHDK includes the ability to call Canon Event Procedures and arbitrary machine code functions. Together these are referred to as "native" calls. As of CHDK 1.2, native function calls may be enabled in the miscellaneous menu. Because there are event procedures and other functions which could permanently damage the camera (for example, by erasing the Canon firmware) this feature is disabled by default and cannot be enabled with set_config_value. If you use a third party script which requires this interface, it is your responsibility to verify that it is safe. If a script attempts to use native call functions when they are not enabled, a Lua error will be triggered. You can check whether native calls are enabled from script using get_config_value.