Introduce a helper function to get a two's complement sample from
the FIFO and munge it to the offset binary format that comedi uses.

Signed-off-by: H Hartley Sweeten <hswee...@visionengravers.com>
Cc: Ian Abbott <abbo...@mev.co.uk>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
v2: as pointed out by the kbuild test robot (less than a hour after
    posting the series), the function should be static.

 drivers/staging/comedi/drivers/quatech_daqp_cs.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/comedi/drivers/quatech_daqp_cs.c 
b/drivers/staging/comedi/drivers/quatech_daqp_cs.c
index d2e9049..96471fc 100644
--- a/drivers/staging/comedi/drivers/quatech_daqp_cs.c
+++ b/drivers/staging/comedi/drivers/quatech_daqp_cs.c
@@ -169,6 +169,20 @@ static int daqp_ai_cancel(struct comedi_device *dev,
        return 0;
 }
 
+static unsigned int daqp_ai_get_sample(struct comedi_device *dev,
+                                      struct comedi_subdevice *s)
+{
+       unsigned int val;
+
+       /*
+        * Get a two's complement sample from the FIFO and
+        * return the munged offset binary value.
+        */
+       val = inb(dev->iobase + DAQP_FIFO);
+       val |= inb(dev->iobase + DAQP_FIFO) << 8;
+       return comedi_offset_munge(s, val);
+}
+
 static irqreturn_t daqp_interrupt(int irq, void *dev_id)
 {
        struct comedi_device *dev = dev_id;
@@ -190,10 +204,7 @@ static irqreturn_t daqp_interrupt(int irq, void *dev_id)
                        break;
                }
 
-               data = inb(dev->iobase + DAQP_FIFO);
-               data |= inb(dev->iobase + DAQP_FIFO) << 8;
-               data ^= 0x8000;
-
+               data = daqp_ai_get_sample(dev, s);
                comedi_buf_write_samples(s, &data, 1);
 
                if (cmd->stop_src == TRIG_COUNT &&
@@ -309,9 +320,7 @@ static int daqp_ai_insn_read(struct comedi_device *dev,
                /* clear the status event flags */
                inb(dev->iobase + DAQP_STATUS);
 
-               data[i] = inb(dev->iobase + DAQP_FIFO);
-               data[i] |= inb(dev->iobase + DAQP_FIFO) << 8;
-               data[i] ^= 0x8000;
+               data[i] = daqp_ai_get_sample(dev, s);
        }
 
        /* stop any conversions and clear the status event flags */
-- 
2.5.1

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