Step 5 of the (*do_cmdtest) validates that the chanlist, chan/range/aref/etc,
is compatible with the actual hardware. At this point in the (*do_cmdtest)
the chanlist is valid, due to checks in the core, so the sanity check is not
needed.

For aesthetics, factor the step 5 code into a helper function. Tidy up the
factored out code.

Signed-off-by: H Hartley Sweeten <hswee...@visionengravers.com>
Cc: Ian Abbott <abbo...@mev.co.uk>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/staging/comedi/drivers/das1800.c | 37 +++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 15 deletions(-)

diff --git a/drivers/staging/comedi/drivers/das1800.c 
b/drivers/staging/comedi/drivers/das1800.c
index c67f67a..b675f4e 100644
--- a/drivers/staging/comedi/drivers/das1800.c
+++ b/drivers/staging/comedi/drivers/das1800.c
@@ -757,7 +757,25 @@ static unsigned int burst_convert_arg(unsigned int 
convert_arg, int round_mode)
        return micro_sec * 1000;
 }
 
-/* test analog input cmd */
+static int das1800_ai_check_chanlist(struct comedi_device *dev,
+                                    struct comedi_subdevice *s,
+                                    struct comedi_cmd *cmd)
+{
+       unsigned int unipolar0 = CR_RANGE(cmd->chanlist[0]) & UNIPOLAR;
+       int i;
+
+       for (i = 1; i < cmd->chanlist_len; i++) {
+               unsigned int unipolar = CR_RANGE(cmd->chanlist[i]) & UNIPOLAR;
+
+               if (unipolar != unipolar0) {
+                       dev_err(dev->class_dev,
+                               "unipolar and bipolar ranges cannot be mixed in 
the chanlist\n");
+                       return -EINVAL;
+               }
+       }
+       return 0;
+}
+
 static int das1800_ai_do_cmdtest(struct comedi_device *dev,
                                 struct comedi_subdevice *s,
                                 struct comedi_cmd *cmd)
@@ -766,8 +784,6 @@ static int das1800_ai_do_cmdtest(struct comedi_device *dev,
        struct das1800_private *devpriv = dev->private;
        int err = 0;
        unsigned int tmp_arg;
-       int i;
-       int unipolar;
 
        /* Step 1 : check if triggers are trivially valid */
 
@@ -872,18 +888,9 @@ static int das1800_ai_do_cmdtest(struct comedi_device *dev,
        if (err)
                return 4;
 
-       /*  make sure user is not trying to mix unipolar and bipolar ranges */
-       if (cmd->chanlist) {
-               unipolar = CR_RANGE(cmd->chanlist[0]) & UNIPOLAR;
-               for (i = 1; i < cmd->chanlist_len; i++) {
-                       if (unipolar != (CR_RANGE(cmd->chanlist[i]) & 
UNIPOLAR)) {
-                               comedi_error(dev,
-                                            "unipolar and bipolar ranges 
cannot be mixed in the chanlist");
-                               err++;
-                               break;
-                       }
-               }
-       }
+       /* Step 5: check channel list */
+
+       err |= das1800_ai_check_chanlist(dev, s, cmd);
 
        if (err)
                return 5;
-- 
1.8.5.2

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