staging: comedi: cb_pcidas: use subdevice readback for 'trimpot_value'

Use the comedi_subdevice 'readback' member and the core provided (*insn_read)
to handle the readback of the write-only trimpot calib subdevice. Remove the
then unused 'trimpot_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>

1 files changed, 8 insertions, 18 deletions

diff --git a/drivers/staging/comedi/drivers/cb_pcidas.c b/drivers/staging/comedi/drivers/cb_pcidas.c
index d5edb5f..86e3d20 100644
--- a/drivers/staging/comedi/drivers/cb_pcidas.c
+++ b/drivers/staging/comedi/drivers/cb_pcidas.c
@@ -356,7 +356,6 @@ struct cb_pcidas_private {
 	/* divisors of master clock for analog output pacing */
 	unsigned int ao_divisor1;
 	unsigned int ao_divisor2;
-	unsigned int trimpot_value[NUM_CHANNELS_8402];
 	unsigned int dac08_value;
 	unsigned int calibration_source;
 };
@@ -744,33 +743,20 @@ static int cb_pcidas_trimpot_insn_write(struct comedi_device *dev,
 					struct comedi_insn *insn,
 					unsigned int *data)
 {
-	struct cb_pcidas_private *devpriv = dev->private;
 	unsigned int chan = CR_CHAN(insn->chanspec);
 
 	if (insn->n) {
 		unsigned int val = data[insn->n - 1];
 
-		if (devpriv->trimpot_value[chan] != val) {
+		if (s->readback[chan] != val) {
 			cb_pcidas_trimpot_write(dev, chan, val);
-			devpriv->trimpot_value[chan] = val;
+			s->readback[chan] = val;
 		}
 	}
 
 	return insn->n;
 }
 
-static int trimpot_read_insn(struct comedi_device *dev,
-			     struct comedi_subdevice *s,
-			     struct comedi_insn *insn, unsigned int *data)
-{
-	struct cb_pcidas_private *devpriv = dev->private;
-	unsigned int channel = CR_CHAN(insn->chanspec);
-
-	data[0] = devpriv->trimpot_value[channel];
-
-	return 1;
-}
-
 static int cb_pcidas_ai_check_chanlist(struct comedi_device *dev,
 				       struct comedi_subdevice *s,
 				       struct comedi_cmd *cmd)
@@ -1527,11 +1513,15 @@ static int cb_pcidas_auto_attach(struct comedi_device *dev,
 		s->n_chan = NUM_CHANNELS_8402;
 		s->maxdata = 0xff;
 	}
-	s->insn_read = trimpot_read_insn;
 	s->insn_write = cb_pcidas_trimpot_insn_write;
+
+	ret = comedi_alloc_subdev_readback(s);
+	if (ret)
+		return ret;
+
 	for (i = 0; i < s->n_chan; i++) {
 		cb_pcidas_trimpot_write(dev, i, s->maxdata / 2);
-		devpriv->trimpot_value[i] = s->maxdata / 2;
+		s->readback[i] = s->maxdata / 2;
 	}
 
 	/*  dac08 caldac */