staging: comedi: ni_mio_common: fix ni_ao_insn_write()

Comedi (*insn_write) functions are expected to write insn->n values
to the hardware. Fix this function to work like the core expects.

Also, don't rely on the return value of ni_ao_comfig_chanlist() to
determine if the values need converted to two's complement before
writing to the hardware. Use the comedi_range_is_bipolar() and
comedi_offset_munge() helpers to clarify the 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/ni_mio_common.c

@@ -3079,23 +3079,43 @@ static int ni_ao_insn_read(struct comedi_device *dev,
 
 static int ni_ao_insn_write(struct comedi_device *dev,
 			    struct comedi_subdevice *s,
-			    struct comedi_insn *insn, unsigned int *data)
+			    struct comedi_insn *insn,
+			    unsigned int *data)
 {
 	struct ni_private *devpriv = dev->private;
 	unsigned int chan = CR_CHAN(insn->chanspec);
-	unsigned int invert;
+	unsigned int range = CR_RANGE(insn->chanspec);
+	int reg;
+	int i;
+
+	if (devpriv->is_m_series)
+		reg = M_Offset_DAC_Direct_Data(chan);
+	else
+		reg = (chan) ? DAC1_Direct_Data : DAC0_Direct_Data;
+
+	ni_ao_config_chanlist(dev, s, &insn->chanspec, 1, 0);
 
-	invert = ni_ao_config_chanlist(dev, s, &insn->chanspec, 1, 0);
+	for (i = 0; i < insn->n; i++) {
+		unsigned int val = data[i];
 
-	devpriv->ao[chan] = data[0];
+		devpriv->ao[chan] = val;
 
 		if (devpriv->is_m_series) {
-		ni_writew(dev, data[0], M_Offset_DAC_Direct_Data(chan));
-	} else
-		ni_writew(dev, data[0] ^ invert,
-			  (chan) ? DAC1_Direct_Data : DAC0_Direct_Data);
+			/* M-series board always use offset binary values */
+			ni_writew(dev, val, reg);
+		} else {
+			/*
+			 * Non-M series boards need two's complement values
+			 * for bipolar ranges.
+			 */
+			if (comedi_range_is_bipolar(s, range))
+				val = comedi_offset_munge(s, val);
 
-	return 1;
+			ni_writew(dev, val, reg);
+		}
+	}
+
+	return insn->n;
 }
 
 static int ni_ao_insn_write_671x(struct comedi_device *dev,