We can read objects :-)

src/cryptoki.hxx

@@ -668,7 +668,8 @@ namespace cryptoki {
       /*! @param slot slot to open a session on */
       Session(Slot& slot): _slot(slot), _session(0), _res(CKR_OK) {
         //! calls @c C_OpenSession
-        check(_slot._init->_fn->C_OpenSession(_slot._slot, 0, 0, 0, &_session),
+        check(_slot._init->_fn->C_OpenSession
+              (_slot._slot, CKF_SERIAL_SESSION, 0, 0, &_session),
               CRYPTOKI_FN_LOG("C_OpenSession"));
         //! @todo pass parameter
       }