const struct pcl818_board *board = comedi_board(dev);
        struct pcl818_private *devpriv = dev->private;
        int err = 0;
-       int tmp;
+       unsigned int arg;
 
        /* Step 1 : check if triggers are trivially valid */
 
        /* step 4: fix up any arguments */
 
        if (cmd->convert_src == TRIG_TIMER) {
-               tmp = cmd->convert_arg;
+               arg = cmd->convert_arg;
                i8253_cascade_ns_to_timer(devpriv->i8253_osc_base,
                                          &devpriv->divisor1,
                                          &devpriv->divisor2,
-                                         &cmd->convert_arg, cmd->flags);
-               if (cmd->convert_arg < board->ns_min)
-                       cmd->convert_arg = board->ns_min;
-               if (tmp != cmd->convert_arg)
-                       err++;
+                                         &arg, cmd->flags);
+               err |= cfc_check_trigger_arg_is(&cmd->convert_arg, arg);
        }
 
        if (err)