There are various type of return codes that SM sends from it's method. The full list with their purpose is as below :
SmFailureExit = -3, /**< enum value SmFailureExit. Exit with failure. NOT preferrable, Use SmFailure if possible.*/
SmNotImplemented = -2, /**< enum value SmNotImplemented. Method is not implemented */
SmFailure = -1, /**< enum value SmFailure. Method failed */
SmNoAction = 0, /**< enum value SmNoAction. Method took no action */
SmSuccess = 1, /**< enum value SmSuccess. Method succeeded */
SmYes = 2, /**< enum value SmYes. Is used in methods that return boolean YES/NO */
SmNo = 3, /**< enum value SmNo. Is used in methods that return boolean YES/NO */
SmComplete = 4, /**< enum value SmComplete. Method not only succeeded, but completed a processing task. */
SmExit = 5, /**< enum value SmExit. Method not only succeeded, but completed a processing task and requests that processing exit. */
SmRetry = 6 /**< enum value SmRetry. Method should be called again */