staging: comedi: adv_pci1724: use subdevice readback for 'gain_value'

Use the comedi_subdevice 'readback' member and the core provided (*insn_read)
to handle the readback of the write-only gain calib subdevice. Remove the
then unused 'gain_value' member from the private data.

The private data is now unnecessary. Remove it and the allocation.

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>

diff --git a/drivers/staging/comedi/drivers/adv_pci1724.c b/drivers/staging/comedi/drivers/adv_pci1724.c
index 4aa1631de547777c6b23699190e6170577adcdfb..735522876c8091183b7d858556bcae5b2e532fe6 100644 (file)
--- a/drivers/staging/comedi/drivers/adv_pci1724.c
+++ b/drivers/staging/comedi/drivers/adv_pci1724.c
@@ -125,11 +125,6 @@ static const struct comedi_lrange ao_ranges_1724 = {
        }
 };
 
-/* this structure is for data unique to this hardware driver. */
-struct adv_pci1724_private {
-       int gain_value[NUM_AO_CHANNELS];
-};
-
 static int wait_for_dac_idle(struct comedi_device *dev)
 {
        static const int timeout = 10000;
@@ -209,7 +204,6 @@ static int gain_write_insn(struct comedi_device *dev,
                           struct comedi_subdevice *s,
                           struct comedi_insn *insn, unsigned int *data)
 {
-       struct adv_pci1724_private *devpriv = dev->private;
        int channel = CR_CHAN(insn->chanspec);
        int retval;
        int i;
@@ -221,27 +215,8 @@ static int gain_write_insn(struct comedi_device *dev,
                retval = set_dac(dev, DAC_GAIN_MODE, channel, data[i]);
                if (retval < 0)
                        return retval;
-               devpriv->gain_value[channel] = data[i];
-       }
-
-       return insn->n;
-}
-
-static int gain_read_insn(struct comedi_device *dev,
-                         struct comedi_subdevice *s, struct comedi_insn *insn,
-                         unsigned int *data)
-{
-       struct adv_pci1724_private *devpriv = dev->private;
-       unsigned int channel = CR_CHAN(insn->chanspec);
-       int i;
-
-       if (devpriv->gain_value[channel] < 0) {
-               dev_err(dev->class_dev,
-                       "Cannot read back channels which have not yet been written to\n");
-               return -EIO;
+               s->readback[channel] = data[i];
        }
-       for (i = 0; i < insn->n; i++)
-               data[i] = devpriv->gain_value[channel];
 
        return insn->n;
 }
@@ -287,9 +262,12 @@ static int setup_subdevices(struct comedi_device *dev)
        s->type = COMEDI_SUBD_CALIB;
        s->subdev_flags = SDF_READABLE | SDF_WRITABLE | SDF_INTERNAL;
        s->n_chan = NUM_AO_CHANNELS;
-       s->insn_read = gain_read_insn;
-       s->insn_write = gain_write_insn;
        s->maxdata = 0x3fff;
+       s->insn_write = gain_write_insn;
+
+       ret = comedi_alloc_subdev_readback(s);
+       if (ret)
+               return ret;
 
        return 0;
 }
@@ -298,21 +276,9 @@ static int adv_pci1724_auto_attach(struct comedi_device *dev,
                                   unsigned long context_unused)
 {
        struct pci_dev *pcidev = comedi_to_pci_dev(dev);
-       struct adv_pci1724_private *devpriv;
-       int i;
        int retval;
        unsigned int board_id;
 
-       devpriv = comedi_alloc_devpriv(dev, sizeof(*devpriv));
-       if (!devpriv)
-               return -ENOMEM;
-
-       /* init software copies of output values to indicate we don't know
-        * what the output value is since it has never been written. */
-       for (i = 0; i < NUM_AO_CHANNELS; ++i) {
-               devpriv->gain_value[i] = -1;
-       }
-
        retval = comedi_pci_enable(dev);
        if (retval)
                return retval;