staging: comedi: adv_pci1710: 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/adv_pci1710.c

@@ -285,7 +285,6 @@ struct pci1710_private {
 	unsigned int act_chanlist[32];	/*  list of scanned channel */
 	unsigned char saved_seglen;	/* len of the non-repeating chanlist */
 	unsigned char da_ranges;	/*  copy of D/A outpit range register */
-	unsigned short ao_data[4];	/*  data output buffer */
 	unsigned int cnt0_write_wait;	/* after a write, wait for update of the
 					 * internal state */
 };
@@ -491,36 +490,19 @@ static int pci171x_insn_write_ao(struct comedi_device *dev,
 		outw(devpriv->da_ranges, dev->iobase + PCI171x_DAREF);
 		ofs = PCI171x_DA1;
 	}
-	val = devpriv->ao_data[chan];
+	val = s->readback[chan];
 
 	for (n = 0; n < insn->n; n++) {
 		val = data[n];
 		outw(val, dev->iobase + ofs);
 	}
 
-	devpriv->ao_data[chan] = val;
+	s->readback[chan] = val;
 
 	return n;
 
 }
 
-/*
-==============================================================================
-*/
-static int pci171x_insn_read_ao(struct comedi_device *dev,
-				struct comedi_subdevice *s,
-				struct comedi_insn *insn, unsigned int *data)
-{
-	struct pci1710_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;
-}
-
 /*
 ==============================================================================
 */
@@ -672,7 +654,7 @@ static int pci1720_insn_write_ao(struct comedi_device *dev,
 		outb(rangereg, dev->iobase + PCI1720_RANGE);
 		devpriv->da_ranges = rangereg;
 	}
-	val = devpriv->ao_data[chan];
+	val = s->readback[chan];
 
 	for (n = 0; n < insn->n; n++) {
 		val = data[n];
@@ -680,7 +662,7 @@ static int pci1720_insn_write_ao(struct comedi_device *dev,
 		outb(0, dev->iobase + PCI1720_SYNCOUT);	/*  update outputs */
 	}
 
-	devpriv->ao_data[chan] = val;
+	s->readback[chan] = val;
 
 	return n;
 }
@@ -1012,9 +994,7 @@ static int pci171x_reset(struct comedi_device *dev)
 		/* set DACs to 0..5V */
 		outb(devpriv->da_ranges, dev->iobase + PCI171x_DAREF);
 		outw(0, dev->iobase + PCI171x_DA1); /* set DA outputs to 0V */
-		devpriv->ao_data[0] = 0x0000;
 		outw(0, dev->iobase + PCI171x_DA2);
-		devpriv->ao_data[1] = 0x0000;
 	}
 	outw(0, dev->iobase + PCI171x_DO);	/*  digital outputs to 0 */
 	outb(0, dev->iobase + PCI171x_CLRFIFO);	/*  clear FIFO */
@@ -1039,10 +1019,7 @@ static int pci1720_reset(struct comedi_device *dev)
 	outw(0x0800, dev->iobase + PCI1720_DA2);
 	outw(0x0800, dev->iobase + PCI1720_DA3);
 	outb(0, dev->iobase + PCI1720_SYNCOUT);	/*  update outputs */
-	devpriv->ao_data[0] = 0x0800;
-	devpriv->ao_data[1] = 0x0800;
-	devpriv->ao_data[2] = 0x0800;
-	devpriv->ao_data[3] = 0x0800;
+
 	return 0;
 }
 
@@ -1148,7 +1125,19 @@ static int pci1710_auto_attach(struct comedi_device *dev,
 			s->insn_write = pci171x_insn_write_ao;
 			break;
 		}
-		s->insn_read = pci171x_insn_read_ao;
+
+		ret = comedi_alloc_subdev_readback(s);
+		if (ret)
+			return ret;
+
+		/* initialize the readback values to match the board reset */
+		if (this_board->cardtype == TYPE_PCI1720) {
+			int i;
+
+			for (i = 0; i < s->n_chan; i++)
+				s->readback[i] = 0x0800;
+		}
+
 		subdev++;
 	}