typedef void (elevator_activate_req_fn) (request_queue_t *, struct request *);
typedef void (elevator_deactivate_req_fn) (request_queue_t *, struct request *);
-typedef int (elevator_init_fn) (request_queue_t *, elevator_t *);
+typedef void *(elevator_init_fn) (request_queue_t *, elevator_t *);
typedef void (elevator_exit_fn) (elevator_t *);
struct elevator_ops