staging: comedi: ni_labpc_common: use subdevice readback for analog outputs

Use the comedi_subdevice 'readback' member and the core provided (*insn_read)
to handle the readback of the analog output subdevice. Remove the then unused
'ao_value' member from the private 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>

2 files changed, 5 insertions, 16 deletions

diff --git a/drivers/staging/comedi/drivers/ni_labpc.h b/drivers/staging/comedi/drivers/ni_labpc.h
index 3261e22..e6a95f9 100644
--- a/drivers/staging/comedi/drivers/ni_labpc.h
+++ b/drivers/staging/comedi/drivers/ni_labpc.h
@@ -37,8 +37,6 @@ struct labpc_boardinfo {
 struct labpc_private {
 	/*  number of data points left to be taken */
 	unsigned long long count;
-	/*  software copy of analog output values */
-	unsigned int ao_value[NUM_AO_CHAN];
 	/*  software copys of bits written to command registers */
 	unsigned int cmd1;
 	unsigned int cmd2;
diff --git a/drivers/staging/comedi/drivers/ni_labpc_common.c b/drivers/staging/comedi/drivers/ni_labpc_common.c
index 354c33e..a6c63b5 100644
--- a/drivers/staging/comedi/drivers/ni_labpc_common.c
+++ b/drivers/staging/comedi/drivers/ni_labpc_common.c
@@ -927,7 +927,7 @@ static void labpc_ao_write(struct comedi_device *dev,
 	devpriv->write_byte(dev, val & 0xff, DAC_LSB_REG(chan));
 	devpriv->write_byte(dev, (val >> 8) & 0xff, DAC_MSB_REG(chan));
 
-	devpriv->ao_value[chan] = val;
+	s->readback[chan] = val;
 }
 
 static int labpc_ao_insn_write(struct comedi_device *dev,
@@ -966,18 +966,6 @@ static int labpc_ao_insn_write(struct comedi_device *dev,
 	return 1;
 }
 
-static int labpc_ao_insn_read(struct comedi_device *dev,
-			      struct comedi_subdevice *s,
-			      struct comedi_insn *insn,
-			      unsigned int *data)
-{
-	struct labpc_private *devpriv = dev->private;
-
-	data[0] = devpriv->ao_value[CR_CHAN(insn->chanspec)];
-
-	return 1;
-}
-
 /* lowlevel write to eeprom/dac */
 static void labpc_serial_out(struct comedi_device *dev, unsigned int value,
 			     unsigned int value_width)
@@ -1301,9 +1289,12 @@ int labpc_common_attach(struct comedi_device *dev,
 		s->n_chan	= NUM_AO_CHAN;
 		s->maxdata	= 0x0fff;
 		s->range_table	= &range_labpc_ao;
-		s->insn_read	= labpc_ao_insn_read;
 		s->insn_write	= labpc_ao_insn_write;
 
+		ret = comedi_alloc_subdev_readback(s);
+		if (ret)
+			return ret;
+
 		/* initialize analog outputs to a known value */
 		for (i = 0; i < s->n_chan; i++)
 			labpc_ao_write(dev, s, i, s->maxdata / 2);