staging: comedi: dmm32at: factor out chanlist checking from (*do_cmdtest)

Step 5 of the (*do_cmdtest) validates that the cmd->chanlist is compatible
with the hardware.

For aesthetics, factor out the step 5 code for the analog input async command
support. Tidy up the factored out code.

To minimize the noise, change the comedi_error(), which is a wrapper around
dev_err(), to dev_dbg().
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/dmm32at.c

@@ -243,13 +243,39 @@ static int dmm32at_ns_to_timer(unsigned int *ns, int round)
 	return *ns;
 }
 
+static int dmm32at_ai_check_chanlist(struct comedi_device *dev,
+				     struct comedi_subdevice *s,
+				     struct comedi_cmd *cmd)
+{
+	unsigned int chan0 = CR_CHAN(cmd->chanlist[0]);
+	unsigned int range0 = CR_RANGE(cmd->chanlist[0]);
+	int i;
+
+	for (i = 1; i < cmd->chanlist_len; i++) {
+		unsigned int chan = CR_CHAN(cmd->chanlist[i]);
+		unsigned int range = CR_RANGE(cmd->chanlist[i]);
+
+		if (chan != (chan0 + i) % s->n_chan) {
+			dev_dbg(dev->class_dev,
+				"entries in chanlist must be consecutive channels, counting upwards\n");
+			return -EINVAL;
+		}
+		if (range != range0) {
+			dev_dbg(dev->class_dev,
+				"entries in chanlist must all have the same gain\n");
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
 static int dmm32at_ai_cmdtest(struct comedi_device *dev,
 			      struct comedi_subdevice *s,
 			      struct comedi_cmd *cmd)
 {
 	int err = 0;
 	int tmp;
-	int start_chan, gain, i;
 
 	/* Step 1 : check if triggers are trivially valid */
 
@@ -349,26 +375,9 @@ static int dmm32at_ai_cmdtest(struct comedi_device *dev,
 	if (err)
 		return 4;
 
-	/* step 5 check the channel list, the channel list for this
-	   board must be consecutive and gains must be the same */
-
-	if (cmd->chanlist) {
-		gain = CR_RANGE(cmd->chanlist[0]);
-		start_chan = CR_CHAN(cmd->chanlist[0]);
-		for (i = 1; i < cmd->chanlist_len; i++) {
-			if (CR_CHAN(cmd->chanlist[i]) !=
-			    (start_chan + i) % s->n_chan) {
-				comedi_error(dev,
-					     "entries in chanlist must be consecutive channels, counting upwards\n");
-				err++;
-			}
-			if (CR_RANGE(cmd->chanlist[i]) != gain) {
-				comedi_error(dev,
-					     "entries in chanlist must all have the same gain\n");
-				err++;
-			}
-		}
-	}
+	/* Step 5: check channel list if it exists */
+	if (cmd->chanlist && cmd->chanlist_len > 0)
+		err |= dmm32at_ai_check_chanlist(dev, s, cmd);
 
 	if (err)
 		return 5;