staging: comedi: usbdux: clarify bipolar ai data

Use the comedi_range_is_bipolar() helper instead of checking the
'range' index against a magic number.

Also, use the s->maxdata to calculate the value needed to munge the
value for bipolar data instead of the magic number.

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>

diff --git a/drivers/staging/comedi/drivers/usbdux.c b/drivers/staging/comedi/drivers/usbdux.c
index a536fa3..a81b4b1 100644 (file)
--- a/drivers/staging/comedi/drivers/usbdux.c
+++ b/drivers/staging/comedi/drivers/usbdux.c
@@ -1002,8 +1002,10 @@ static int usbdux_ai_insn_read(struct comedi_device *dev,
                        goto ai_read_exit;
 
                val = le16_to_cpu(devpriv->insn_buffer[1]);
-               if (range <= 1)
-                       val ^= 0x800;
+
+               /* bipolar data is two's-complement */
+               if (comedi_range_is_bipolar(s, range))
+                       val ^= ((s->maxdata + 1) >> 1);
 
                data[i] = val;
        }