If you aren't expecting extended types (xtype)

The following code sample demonstrates how to handle the case where you're not expecting any extended types. In this case, if you get a message that contains an xtype, you should reply with ENOSYS. The example can be used in either an io_read or io_write handler.

int io_read (resmgr_context_t *ctp, io_read_t *msg, RESMGR_OCB_T *ocb)
{
    int    status;

    if ((status = iofunc_read_verify(ctp, msg, ocb, NULL)) != EOK) {
        return (status);
    }

    /* No special xtypes */
    if ((msg->i.xtype & _IO_XTYPE_MASK) != _IO_XTYPE_NONE)
        return (ENOSYS);
    ...
}