Function snd_config_expand_custom 

pub unsafe extern "C" fn snd_config_expand_custom(
    config: *mut snd_config_t,
    root: *mut snd_config_t,
    fcn: snd_config_expand_fcn_t,
    private_data: *mut c_void,
    result: *mut *mut snd_config_t,
) -> c_int