Only the last value needs to be saved for readback.
Remove the LSB and MSB macros.
(*insn_write) functions should return an errno or the number of
samples actually read. Change the final return to insn->n to
make this clear.
Signed-off-by: H Hartley Sweeten <hswee...@visionengravers.com>
Cc: Ian Abbott <abbo...@mev.co.uk>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
drivers/staging/comedi/drivers/pcmda12.c | 32 ++++++++++++--------------------
1 file changed, 12 insertions(+), 20 deletions(-)
diff --git a/drivers/staging/comedi/drivers/pcmda12.c
b/drivers/staging/comedi/drivers/pcmda12.c
index c61c2c1..2b62894 100644
--- a/drivers/staging/comedi/drivers/pcmda12.c
+++ b/drivers/staging/comedi/drivers/pcmda12.c
@@ -51,8 +51,6 @@ Configuration Options:
#define CHANS 8
#define IOSIZE 16
-#define LSB(x) ((unsigned char)((x) & 0xff))
-#define MSB(x) ((unsigned char)((((unsigned short)(x))>>8) & 0xff))
#define LSB_PORT(chan) (dev->iobase + (chan)*2)
#define MSB_PORT(chan) (LSB_PORT(chan)+1)
@@ -90,31 +88,25 @@ static int pcmda12_ao_insn_write(struct comedi_device *dev,
unsigned int *data)
{
struct pcmda12_private *devpriv = dev->private;
+ unsigned int chan = CR_CHAN(insn->chanspec);
+ unsigned int val = devpriv->ao_readback[chan];
int i;
- int chan = CR_CHAN(insn->chanspec);
- /* Writing a list of values to an AO channel is probably not
- * very useful, but that's how the interface is defined. */
for (i = 0; i < insn->n; ++i) {
-
-/* /\* do this as one instruction?? *\/ */
-/* outw(data[i], LSB_PORT(chan)); */
-
- /* Need to do this as two instructions due to 8-bit bus?? */
- /* first, load the low byte */
- outb(LSB(data[i]), LSB_PORT(chan));
- /* next, write the high byte */
- outb(MSB(data[i]), MSB_PORT(chan));
-
- /* save shadow register */
- devpriv->ao_readback[chan] = data[i];
-
+ val = data[i];
+ outb(val & 0xff, LSB_PORT(chan));
+ outb((val >> 8) & 0xff, MSB_PORT(chan));
+
+ /*
+ * Initiate transfer if not in simultaneaous xfer
+ * mode by reading one of the AO registers.
+ */
if (!devpriv->simultaneous_xfer_mode)
inb(LSB_PORT(chan));
}
+ devpriv->ao_readback[chan] = val;
- /* return the number of samples written */
- return i;
+ return insn->n;
}
static int pcmda12_ao_insn_read(struct comedi_device *dev,
--
1.8.1.4
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