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    Subject[PATCH 3.5 46/60] staging: comedi: adv_pci1710: fix analog output readback value
    Date
    3.5.7.31 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: H Hartley Sweeten <hsweeten@visionengravers.com>

    commit 1e85c1ea1ff2a60659e790ef8ec76c7339445841 upstream.

    The last value written to a analog output channel is cached in the
    private data of this driver for readback.

    Currently, the wrong value is cached in the (*insn_write) functions.
    The current code stores the data[n] value for readback afer the loop
    has written all the values. At this time 'n' points past the end of
    the data array.

    Fix the functions by using a local variable to hold the data being
    written to the analog output channel. This variable is then used
    after the loop is complete to store the readback value. The current
    value is retrieved before the loop in case no values are actually
    written..

    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>
    [ luis: backported to 3.5: adjusted context ]
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    drivers/staging/comedi/drivers/adv_pci1710.c | 17 ++++++++++++-----
    1 file changed, 12 insertions(+), 5 deletions(-)

    diff --git a/drivers/staging/comedi/drivers/adv_pci1710.c b/drivers/staging/comedi/drivers/adv_pci1710.c
    index de8c98c..555790c 100644
    --- a/drivers/staging/comedi/drivers/adv_pci1710.c
    +++ b/drivers/staging/comedi/drivers/adv_pci1710.c
    @@ -387,6 +387,7 @@ static int pci171x_insn_write_ao(struct comedi_device *dev,
    struct comedi_subdevice *s,
    struct comedi_insn *insn, unsigned int *data)
    {
    + unsigned int val;
    int n, chan, range, ofs;

    chan = CR_CHAN(insn->chanspec);
    @@ -402,11 +403,14 @@ 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];

    - for (n = 0; n < insn->n; n++)
    - outw(data[n], dev->iobase + ofs);
    + for (n = 0; n < insn->n; n++) {
    + val = data[n];
    + outw(val, dev->iobase + ofs);
    + }

    - devpriv->ao_data[chan] = data[n];
    + devpriv->ao_data[chan] = val;

    return n;

    @@ -555,6 +559,7 @@ static int pci1720_insn_write_ao(struct comedi_device *dev,
    struct comedi_subdevice *s,
    struct comedi_insn *insn, unsigned int *data)
    {
    + unsigned int val;
    int n, rangereg, chan;

    chan = CR_CHAN(insn->chanspec);
    @@ -564,13 +569,15 @@ 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];

    for (n = 0; n < insn->n; n++) {
    - outw(data[n], dev->iobase + PCI1720_DA0 + (chan << 1));
    + val = data[n];
    + outw(val, dev->iobase + PCI1720_DA0 + (chan << 1));
    outb(0, dev->iobase + PCI1720_SYNCOUT); /* update outputs */
    }

    - devpriv->ao_data[chan] = data[n];
    + devpriv->ao_data[chan] = val;

    return n;
    }
    --
    1.9.0


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