staging: comedi: pcl818: tidy up the analog output subdevice

For aesthetics, tidy up the analog output subdevice code.

Change the regsiter map defines to simplify the code.

Move the analog subdevice support functions out of the analog input
support functions. Tidy them up a bit during the move.

Reverse the logic of the subdevice init and add some whitespace.
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/pcl818.c

@@ -136,14 +136,10 @@ A word or two about DMA. Driver support DMA operations at two ways:
 #define PCL818_AD_LO 0
 /* R: high byte of A/D W: A/D range control */
 #define PCL818_AD_HI 1
-/* W: D/A low&high byte */
-#define PCL818_DA_LO 4
-#define PCL818_DA_HI 5
+#define PCL818_AO_LSB_REG(x)			(0x04 + ((x) * 2))
+#define PCL818_AO_MSB_REG(x)			(0x05 + ((x) * 2))
 #define PCL818_DO_DI_LSB_REG			0x03
 #define PCL818_DO_DI_MSB_REG			0x0b
-/* W: PCL718 second D/A */
-#define PCL718_DA2_LO 6
-#define PCL718_DA2_HI 7
 
 #define PCL818_TIMER_BASE			0x0c
 
@@ -484,39 +480,6 @@ static int pcl818_ai_insn_read(struct comedi_device *dev,
 	return n;
 }
 
-static int pcl818_ao_insn_read(struct comedi_device *dev,
-			       struct comedi_subdevice *s,
-			       struct comedi_insn *insn, unsigned int *data)
-{
-	struct pcl818_private *devpriv = dev->private;
-	int n;
-	int chan = CR_CHAN(insn->chanspec);
-
-	for (n = 0; n < insn->n; n++)
-		data[n] = devpriv->ao_readback[chan];
-
-	return n;
-}
-
-static int pcl818_ao_insn_write(struct comedi_device *dev,
-				struct comedi_subdevice *s,
-				struct comedi_insn *insn, unsigned int *data)
-{
-	struct pcl818_private *devpriv = dev->private;
-	int n;
-	int chan = CR_CHAN(insn->chanspec);
-
-	for (n = 0; n < insn->n; n++) {
-		devpriv->ao_readback[chan] = data[n];
-		outb((data[n] & 0x000f) << 4, dev->iobase +
-		     (chan ? PCL718_DA2_LO : PCL818_DA_LO));
-		outb((data[n] & 0x0ff0) >> 4, dev->iobase +
-		     (chan ? PCL718_DA2_HI : PCL818_DA_HI));
-	}
-
-	return n;
-}
-
 static bool pcl818_ai_dropout(struct comedi_device *dev,
 			      struct comedi_subdevice *s,
 			      unsigned int chan)
@@ -1000,6 +963,41 @@ static int pcl818_ai_cancel(struct comedi_device *dev,
 	return 0;
 }
 
+static int pcl818_ao_insn_write(struct comedi_device *dev,
+				struct comedi_subdevice *s,
+				struct comedi_insn *insn,
+				unsigned int *data)
+{
+	struct pcl818_private *devpriv = dev->private;
+	unsigned int chan = CR_CHAN(insn->chanspec);
+	int i;
+
+	for (i = 0; i < insn->n; i++) {
+		devpriv->ao_readback[chan] = data[i];
+		outb((data[i] & 0x000f) << 4,
+		     dev->iobase + PCL818_AO_LSB_REG(chan));
+		outb((data[i] & 0x0ff0) >> 4,
+		     dev->iobase + PCL818_AO_MSB_REG(chan));
+	}
+
+	return insn->n;
+}
+
+static int pcl818_ao_insn_read(struct comedi_device *dev,
+			       struct comedi_subdevice *s,
+			       struct comedi_insn *insn,
+			       unsigned int *data)
+{
+	struct pcl818_private *devpriv = dev->private;
+	unsigned int chan = CR_CHAN(insn->chanspec);
+	int i;
+
+	for (i = 0; i < insn->n; i++)
+		data[i] = devpriv->ao_readback[chan];
+
+	return insn->n;
+}
+
 static int pcl818_di_insn_bits(struct comedi_device *dev,
 			       struct comedi_subdevice *s,
 			       struct comedi_insn *insn,
@@ -1037,8 +1035,9 @@ static void pcl818_reset(struct comedi_device *dev)
 		outb(0, dev->iobase + PCL818_FI_FLUSH);
 		outb(0, dev->iobase + PCL818_FI_ENABLE);
 	}
-	outb(0, dev->iobase + PCL818_DA_LO);	/*  DAC=0V */
-	outb(0, dev->iobase + PCL818_DA_HI);
+	/* set analog output channel 0 to 0V */
+	outb(0, dev->iobase + PCL818_AO_LSB_REG(0));
+	outb(0, dev->iobase + PCL818_AO_MSB_REG(0));
 	udelay(1);
 	outb(0, dev->iobase + PCL818_DO_DI_MSB_REG);
 	outb(0, dev->iobase + PCL818_DO_DI_LSB_REG);
@@ -1056,8 +1055,9 @@ static void pcl818_reset(struct comedi_device *dev)
 	if (board->is_818) {
 		outb(0, dev->iobase + PCL818_RANGE);
 	} else {
-		outb(0, dev->iobase + PCL718_DA2_LO);
-		outb(0, dev->iobase + PCL718_DA2_HI);
+		/* set analog output channel 1 to 0V */
+		outb(0, dev->iobase + PCL818_AO_LSB_REG(1));
+		outb(0, dev->iobase + PCL818_AO_MSB_REG(1));
 	}
 }
 
@@ -1196,10 +1196,9 @@ static int pcl818_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 		s->cancel	= pcl818_ai_cancel;
 	}
 
+	/* Analog Output subdevice */
 	s = &dev->subdevices[1];
-	if (!board->n_aochan) {
-		s->type = COMEDI_SUBD_UNUSED;
-	} else {
+	if (board->n_aochan) {
 		s->type		= COMEDI_SUBD_AO;
 		s->subdev_flags	= SDF_WRITABLE | SDF_GROUND;
 		s->n_chan	= board->n_aochan;
@@ -1218,6 +1217,8 @@ static int pcl818_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 			if (it->options[5] == 2)
 				s->range_table = &range_unknown;
 		}
+	} else {
+		s->type		= COMEDI_SUBD_UNUSED;
 	}
 
 	/* Digital Input subdevice */