diff --git a/drivers/staging/comedi/drivers/acl7225b.c b/drivers/staging/comedi/drivers/acl7225b.c
index 80cfa817dd45e6ce23e3068b5b069c81c996ed76..5afadce5a2484885da735b7f3e54cb56f95b7ab3 100644
--- a/drivers/staging/comedi/drivers/acl7225b.c
+++ b/drivers/staging/comedi/drivers/acl7225b.c
@@ -64,8 +64,10 @@ static int acl7225b_di_insn_bits(struct comedi_device *dev,
 				 struct comedi_insn *insn,
 				 unsigned int *data)
 {
-	data[1] = inb(dev->iobase + (unsigned long)s->private) |
-	    (inb(dev->iobase + (unsigned long)s->private + 1) << 8);
+	unsigned long reg = (unsigned long)s->private;
+
+	data[1] = inb(dev->iobase + reg) |
+		  (inb(dev->iobase + reg + 1) << 8);
 
 	return insn->n;
 }