staging: comedi: amplc_pci224: 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 the step 5 code for the analog output async command
support. Tidy up the factored out code.
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/amplc_pci224.c

@@ -687,6 +687,37 @@ pci224_ao_inttrig_start(struct comedi_device *dev, struct comedi_subdevice *s,
 	return 1;
 }
 
+static int pci224_ao_check_chanlist(struct comedi_device *dev,
+				    struct comedi_subdevice *s,
+				    struct comedi_cmd *cmd)
+{
+	unsigned int range0 = CR_RANGE(cmd->chanlist[0]);
+	unsigned int chan_mask = 0;
+	int i;
+
+	for (i = 0; i < cmd->chanlist_len; i++) {
+		unsigned int chan = CR_CHAN(cmd->chanlist[i]);
+		unsigned int range = CR_RANGE(cmd->chanlist[i]);
+
+		if (chan_mask & (1 << chan)) {
+			dev_dbg(dev->class_dev,
+				"%s: entries in chanlist must contain no duplicate channels\n",
+				__func__);
+			return -EINVAL;
+		}
+		chan_mask |= (1 << chan);
+
+		if (range != range0) {
+			dev_dbg(dev->class_dev,
+				"%s: entries in chanlist must all have the same range index\n",
+				__func__);
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
 #define MAX_SCAN_PERIOD		0xFFFFFFFFU
 #define MIN_SCAN_PERIOD		2500
 #define CONVERT_PERIOD		625
@@ -871,48 +902,9 @@ pci224_ao_cmdtest(struct comedi_device *dev, struct comedi_subdevice *s,
 	if (err)
 		return 4;
 
-	/* Step 5: check channel list. */
-
-	if (cmd->chanlist && (cmd->chanlist_len > 0)) {
-		unsigned int range;
-		enum { range_err = 1, dupchan_err = 2, };
-		unsigned errors;
-		unsigned int n;
-		unsigned int ch;
-
-		/*
-		 * Check all channels have the same range index.  Don't care
-		 * about analogue reference, as we can't configure it.
-		 *
-		 * Check the list has no duplicate channels.
-		 */
-		range = CR_RANGE(cmd->chanlist[0]);
-		errors = 0;
-		tmp = 0;
-		for (n = 0; n < cmd->chanlist_len; n++) {
-			ch = CR_CHAN(cmd->chanlist[n]);
-			if (tmp & (1U << ch))
-				errors |= dupchan_err;
-
-			tmp |= (1U << ch);
-			if (CR_RANGE(cmd->chanlist[n]) != range)
-				errors |= range_err;
-
-		}
-		if (errors) {
-			if (errors & dupchan_err) {
-				dev_dbg(dev->class_dev,
-					"%s: entries in chanlist must contain no duplicate channels\n",
-					__func__);
-			}
-			if (errors & range_err) {
-				dev_dbg(dev->class_dev,
-					"%s: entries in chanlist must all have the same range index\n",
-					__func__);
-			}
-			err++;
-		}
-	}
+	/* Step 5: check channel list if it exists */
+	if (cmd->chanlist && cmd->chanlist_len > 0)
+		err |= pci224_ao_check_chanlist(dev, s, cmd);
 
 	if (err)
 		return 5;