NMSettingSerial @NM_SETTING_SERIAL_ERROR_UNKNOWN: @NM_SETTING_SERIAL_ERROR_INVALID_PROPERTY: @NM_SETTING_SERIAL_ERROR_MISSING_PROPERTY: @NM_SETTING_SERIAL_ERROR_MISSING_PPP_SETTING: @void: @Returns: @void: @Returns: @setting: @Returns: @setting: @Returns: @setting: @Returns: @setting: @Returns: @setting: @Returns: