staging: comedi: rti800: save unmunged data for ao readback

The unmunged data should be saved for readback not the munged data.
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/rti800.c

@@ -231,11 +231,13 @@ static int rti800_ao_insn_write(struct comedi_device *dev,
 	unsigned int chan = CR_CHAN(insn->chanspec);
 	int reg_lo = chan ? RTI800_DAC1LO : RTI800_DAC0LO;
 	int reg_hi = chan ? RTI800_DAC1HI : RTI800_DAC0HI;
-	int val = devpriv->ao_readback[chan];
 	int i;
 
 	for (i = 0; i < insn->n; i++) {
-		val = data[i];
+		unsigned int val = data[i];
+
+		devpriv->ao_readback[chan] = val;
+
 		if (devpriv->dac_2comp[chan])
 			val ^= 0x800;
 
@@ -243,8 +245,6 @@ static int rti800_ao_insn_write(struct comedi_device *dev,
 		outb((val >> 8) & 0xff, dev->iobase + reg_hi);
 	}
 
-	devpriv->ao_readback[chan] = val;
-
 	return insn->n;
 }