fsm->protocol, protocol);
                /* stop old protocol */
                if (fsm->protocol == PROTO_HOST)
-                       ret = fsm->ops->start_host(fsm, 0);
+                       ret = otg_start_host(fsm, 0);
                else if (fsm->protocol == PROTO_GADGET)
-                       ret = fsm->ops->start_gadget(fsm, 0);
+                       ret = otg_start_gadget(fsm, 0);
                if (ret)
                        return ret;
 
                /* start new protocol */
                if (protocol == PROTO_HOST)
-                       ret = fsm->ops->start_host(fsm, 1);
+                       ret = otg_start_host(fsm, 1);
                else if (protocol == PROTO_GADGET)
-                       ret = fsm->ops->start_gadget(fsm, 1);
+                       ret = otg_start_gadget(fsm, 1);
                if (ret)
                        return ret;
 
 
        return 0;
 }
 
+static inline int otg_start_host(struct otg_fsm *fsm, int on)
+{
+       if (!fsm->ops->start_host)
+               return -EOPNOTSUPP;
+       return fsm->ops->start_host(fsm, on);
+}
+
+static inline int otg_start_gadget(struct otg_fsm *fsm, int on)
+{
+       if (!fsm->ops->start_gadget)
+               return -EOPNOTSUPP;
+       return fsm->ops->start_gadget(fsm, on);
+}
+
 int otg_statemachine(struct otg_fsm *fsm);
 
 /* Defined by device specific driver, for different timer implementation */