On 2014-02-05 21:59, H Hartley Sweeten wrote:
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@xxxxxxxxxxxxxxxxxxx>
Cc: Ian Abbott <abbotti@xxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
v2: also fix readback in pci1720_insn_write_ao() as pointed out by
Ian Abbott
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 69a8298..f9d6111 100644
--- a/drivers/staging/comedi/drivers/adv_pci1710.c
+++ b/drivers/staging/comedi/drivers/adv_pci1710.c
@@ -494,6 +494,7 @@ static int pci171x_insn_write_ao(struct comedi_device *dev,
struct comedi_insn *insn, unsigned int *data)
{
struct pci1710_private *devpriv = dev->private;
+ unsigned int val;
int n, chan, range, ofs;
chan = CR_CHAN(insn->chanspec);
@@ -509,11 +510,14 @@ 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;
@@ -679,6 +683,7 @@ static int pci1720_insn_write_ao(struct comedi_device *dev,
struct comedi_insn *insn, unsigned int *data)
{
struct pci1710_private *devpriv = dev->private;
+ unsigned int val;
int n, rangereg, chan;
chan = CR_CHAN(insn->chanspec);
@@ -688,13 +693,15 @@ 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;
}
I'd have done:
if (n)
devpriv->ao_data[chan] = val;
and initialized val to 0 (in case the compiler issues a false
"uninitialized" warning), just because it seems a tad more optimizable
that way. It doesn't matter though; your way is fine too!
Reviewed-by: Ian Abbott <abbotti@xxxxxxxxx>
--
-=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@xxxxxxxxx> )=-
-=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=-
_______________________________________________
devel mailing list
devel@xxxxxxxxxxxxxxxxxxxxxx
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
