diff --git a/drivers/staging/comedi/drivers/cb_pcidas64.c b/drivers/staging/comedi/drivers/cb_pcidas64.c
index 61cb560e1bec..e3bfbd4c5def 100644
--- a/drivers/staging/comedi/drivers/cb_pcidas64.c
+++ b/drivers/staging/comedi/drivers/cb_pcidas64.c
@@ -3380,15 +3380,15 @@ static int dio_callback(struct comedi_device *dev,
 }
 
 static int dio_callback_4020(struct comedi_device *dev,
-			     int dir, int port, int data, unsigned long arg)
+			     int dir, int port, int data, unsigned long iobase)
 {
-	void __iomem *iobase = (void __iomem *)arg;
+	struct pcidas64_private *devpriv = dev->private;
 
 	if (dir) {
-		writew(data, iobase + 2 * port);
+		writew(data, devpriv->main_iobase + iobase + 2 * port);
 		return 0;
 	}
-	return readw(iobase + 2 * port);
+	return readw(devpriv->main_iobase + iobase + 2 * port);
 }
 
 static int di_rbits(struct comedi_device *dev, struct comedi_subdevice *s,
@@ -3751,7 +3751,6 @@ static int setup_subdevices(struct comedi_device *dev)
 	const struct pcidas64_board *thisboard = comedi_board(dev);
 	struct pcidas64_private *devpriv = dev->private;
 	struct comedi_subdevice *s;
-	void __iomem *dio_8255_iobase;
 	int i;
 	int ret;
 
@@ -3840,9 +3839,8 @@ static int setup_subdevices(struct comedi_device *dev)
 	s = &dev->subdevices[4];
 	if (thisboard->has_8255) {
 		if (thisboard->layout == LAYOUT_4020) {
-			dio_8255_iobase = devpriv->main_iobase + I8255_4020_REG;
 			ret = subdev_8255_init(dev, s, dio_callback_4020,
-					       (unsigned long)dio_8255_iobase);
+					       I8255_4020_REG);
 		} else {
 			ret = subdev_8255_init(dev, s, dio_callback,
 					       DIO_8255_OFFSET);