},
 };
 
-static inline unsigned ni_65xx_total_num_ports(const struct ni_65xx_board
-                                              *board)
-{
-       return board->num_dio_ports + board->num_di_ports + board->num_do_ports;
-}
-
 struct ni_65xx_private {
        void __iomem *mmio;
 };
 
+static void ni_65xx_disable_input_filters(struct comedi_device *dev)
+{
+       const struct ni_65xx_board *board = comedi_board(dev);
+       struct ni_65xx_private *devpriv = dev->private;
+       unsigned num_ports;
+       int i;
+
+       num_ports = board->num_dio_ports +
+                   board->num_di_ports +
+                   board->num_do_ports;
+
+       /* disable input filtering on all ports */
+       for (i = 0; i < num_ports; ++i)
+               writeb(0x00, devpriv->mmio + NI_65XX_FILTER_ENA(i));
+
+       /* set filter interval to 0 (32bit reg) */
+       writel(0x00000000, devpriv->mmio + NI_65XX_FILTER_REG);
+}
+
 static int ni_65xx_dio_insn_config(struct comedi_device *dev,
                                   struct comedi_subdevice *s,
                                   struct comedi_insn *insn,
                s->cancel       = ni_65xx_intr_cancel;
        }
 
-       for (i = 0; i < ni_65xx_total_num_ports(board); ++i)
-               writeb(0x00, devpriv->mmio + NI_65XX_FILTER_ENA(i));
-
-       /* Set filter interval to 0  (32bit reg) */
-       writel(0x00000000, devpriv->mmio + NI_65XX_FILTER_REG);
+       ni_65xx_disable_input_filters(dev);
 
        return 0;
 }