;;; ....

;;;###autoload
(define-minor-mode example-mode
  "Enables the example mode"
  (if example-mode
      (example-mode-enable)
    (example-mode-disable)))

(defun exmaple-mode-enable ()
  (cond ((not example-mode-config)
         (message "please define example-mode-config before using example-mode")
         ;;; seem to need to do something here to disable the mode
         ;;; otherwise the mode gets enabled, but does not work
         )
        (t  ;;;; go ahead and set up .....
         )))