Staging: comedi: pcl812: Update MUX for multi-channel AI command

For multi-channel AI commands, the interrupt handler is missing code to
switch to the next channel.  Add some (untested) code to handle this.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/comedi/drivers/pcl812.c

@@ -955,6 +955,7 @@ static irqreturn_t interrupt_pcl812_ai_int(int irq, void *d)
 	unsigned int mask, timeout;
 	struct comedi_device *dev = d;
 	struct comedi_subdevice *s = dev->subdevices + 0;
+	unsigned int next_chan;
 
 	s->async->events = 0;
 
@@ -993,11 +994,18 @@ static irqreturn_t interrupt_pcl812_ai_int(int irq, void *d)
 		       ((inb(dev->iobase + PCL812_AD_HI) << 8) |
 			inb(dev->iobase + PCL812_AD_LO)) & mask);
 
+	/* Set up next channel. Added by abbotti 2010-01-20, but untested. */
+	next_chan = s->async->cur_chan + 1;
+	if (next_chan >= devpriv->ai_n_chan)
+		next_chan = 0;
+	if (devpriv->ai_chanlist[s->async->cur_chan] !=
+			devpriv->ai_chanlist[next_chan])
+		setup_range_channel(dev, s, devpriv->ai_chanlist[next_chan], 0);
+
 	outb(0, dev->iobase + PCL812_CLRINT);	/* clear INT request */
 
-	s->async->cur_chan++;
-	if (s->async->cur_chan >= devpriv->ai_n_chan) {	/* one scan done */
-		s->async->cur_chan = 0;
+	s->async->cur_chan = next_chan;
+	if (next_chan == 0) {	/* one scan done */
 		devpriv->ai_act_scan++;
 		if (!(devpriv->ai_neverending))
 			if (devpriv->ai_act_scan >= devpriv->ai_scans) {	/* all data sampled */