staging: comedi: pcl816: factor out the "next ai chan" code

Factor out the code that bumps the counters in the private data that keep
track of what channel is being samples next and when all the data has been
sampled.

Don't clear the events in the driver. The comedi core will clear the events
at the end of the comedi_event().

Make sure the COMEDI_CB_BLOCK event is set when advancing to the next
channel so that when the comedi_event() is finally called the core will
wake the async_queue to return the analog input data.

Also, make sure the COMEDI_CB_EOS event is set at the completion of each
scan.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/pcl816.c

@@ -271,35 +271,45 @@ static int pcl816_ai_insn_read(struct comedi_device *dev,
 	return n;
 }
 
+static bool pcl816_ai_next_chan(struct comedi_device *dev,
+				struct comedi_subdevice *s)
+{
+	struct pcl816_private *devpriv = dev->private;
+	struct comedi_cmd *cmd = &s->async->cmd;
+
+	s->async->events |= COMEDI_CB_BLOCK;
+
+	s->async->cur_chan++;
+	if (s->async->cur_chan >= cmd->chanlist_len) {
+		s->async->cur_chan = 0;
+		devpriv->ai_act_scan++;
+		s->async->events |= COMEDI_CB_EOS;
+	}
+
+	if (cmd->stop_src == TRIG_COUNT &&
+	    devpriv->ai_act_scan >= cmd->stop_arg) {
+		/* all data sampled */
+		s->cancel(dev, s);
+		s->async->events |= COMEDI_CB_EOA;
+		comedi_event(dev, s);
+		return false;
+	}
+
+	return true;
+}
+
 static void transfer_from_dma_buf(struct comedi_device *dev,
 				  struct comedi_subdevice *s,
 				  unsigned short *ptr,
 				  unsigned int bufptr, unsigned int len)
 {
-	struct pcl816_private *devpriv = dev->private;
-	struct comedi_cmd *cmd = &s->async->cmd;
 	int i;
 
-	s->async->events = 0;
-
 	for (i = 0; i < len; i++) {
-
 		comedi_buf_put(s->async, ptr[bufptr++]);
 
-		s->async->cur_chan++;
-		if (s->async->cur_chan >= cmd->chanlist_len) {
-			s->async->cur_chan = 0;
-			devpriv->ai_act_scan++;
-		}
-
-		if (cmd->stop_src == TRIG_COUNT &&
-		    devpriv->ai_act_scan >= cmd->stop_arg) {
-			/* all data sampled */
-			s->cancel(dev, s);
-			s->async->events |= COMEDI_CB_EOA;
-			s->async->events |= COMEDI_CB_BLOCK;
-			break;
-		}
+		if (!pcl816_ai_next_chan(dev, s))
+			return;
 	}
 
 	comedi_event(dev, s);