staging: comedi: adl_pci9118: use comedi_subdevice 'readback'

Use the new comedi_subdevice 'readback' member and the core provided
(*insn_read) for the readback of the analog output subdevice channels.

The board is "reset" prior to the subdevice init. Part of this reset
sets all the analog output channels to 0V. Move the initialization of
the 'readback' values after the 'readback' member has been allocated.
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/adl_pci9118.c

@@ -255,7 +255,6 @@ struct pci9118_private {
 						 * divisors for start of measure
 						 * on external start
 						 */
-	unsigned short ao_data[2];		/* data output buffer */
 	char dma_doublebuf;			/* use double buffering */
 	unsigned int dma_actbuf;		/* which buffer is used now */
 	unsigned short *dmabuf_virt[2];		/*
@@ -523,32 +522,20 @@ static int pci9118_insn_read_ai(struct comedi_device *dev,
 
 static int pci9118_insn_write_ao(struct comedi_device *dev,
 				 struct comedi_subdevice *s,
-				 struct comedi_insn *insn, unsigned int *data)
+				 struct comedi_insn *insn,
+				 unsigned int *data)
 {
-	struct pci9118_private *devpriv = dev->private;
 	unsigned int chan = CR_CHAN(insn->chanspec);
-	int n;
+	unsigned int val = s->readback[chan];
+	int i;
 
-	for (n = 0; n < insn->n; n++) {
-		outl(data[n], dev->iobase + PCI9118_AO_REG(chan));
-		devpriv->ao_data[chan] = data[n];
+	for (i = 0; i < insn->n; i++) {
+		val = data[i];
+		outl(val, dev->iobase + PCI9118_AO_REG(chan));
 	}
+	s->readback[chan] = val;
 
-	return n;
-}
-
-static int pci9118_insn_read_ao(struct comedi_device *dev,
-				struct comedi_subdevice *s,
-				struct comedi_insn *insn, unsigned int *data)
-{
-	struct pci9118_private *devpriv = dev->private;
-	int n, chan;
-
-	chan = CR_CHAN(insn->chanspec);
-	for (n = 0; n < insn->n; n++)
-		data[n] = devpriv->ao_data[chan];
-
-	return n;
+	return insn->n;
 }
 
 static void interrupt_pci9118_ai_mode4_switch(struct comedi_device *dev)
@@ -1701,10 +1688,8 @@ static int pci9118_reset(struct comedi_device *dev)
 						 */
 
 	/* reset analog outputs to 0V */
-	devpriv->ao_data[0] = 2047;
-	devpriv->ao_data[1] = 2047;
-	outl(devpriv->ao_data[0], dev->iobase + PCI9118_AO_REG(0));
-	outl(devpriv->ao_data[1], dev->iobase + PCI9118_AO_REG(1));
+	outl(2047, dev->iobase + PCI9118_AO_REG(0));
+	outl(2047, dev->iobase + PCI9118_AO_REG(1));
 
 	udelay(10);
 	inl(dev->iobase + PCI9118_AI_FIFO_REG);
@@ -1886,7 +1871,15 @@ static int pci9118_common_attach(struct comedi_device *dev, int disable_irq,
 	s->maxdata	= 0x0fff;
 	s->range_table	= &range_bipolar10;
 	s->insn_write	= pci9118_insn_write_ao;
-	s->insn_read	= pci9118_insn_read_ao;
+	s->insn_read	= comedi_readback_insn_read;
+
+	ret = comedi_alloc_subdev_readback(s);
+	if (ret)
+		return ret;
+
+	/* the analog outputs were reset to 0V, make the readback match */
+	for (i = 0; i < s->n_chan; i++)
+		s->readback[i] = 2047;
 
 	/* Digital Input subdevice */
 	s = &dev->subdevices[2];