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staging: comedi: s626: fix value written by s626_set_dac()

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I broke `s626_set_dac()` by changing the type of the `dacdata` parameter
from `short` to `unsigned short`.  It's actually designed to take a
signed value in the range -0x1fff to +0x2000 although values above
0x1fff get clamped to 0x1fff.  (We could change the `maxdata` value to
0x1ffe to avoid the clamping, but `maxdata` values are usually a power
of 2 minus 1.)  The bug results in all negative values passed to the
function being changed to +0x1fff by the clamp.  Change the parameter
type to `int16_t` to fix the problem.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott 2013-11-06 20:45:59 +00:00 committed by Greg Kroah-Hartman
parent 9382c06e2d
commit 3de00ee4ce
1 changed files with 1 additions and 1 deletions
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2
drivers/staging/comedi/drivers/s626.c
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@ -494,7 +494,7 @@ static void s626_send_dac(struct comedi_device *dev, uint32_t val)
* Private helper function: Write setpoint to an application DAC channel. * Private helper function: Write setpoint to an application DAC channel.
*/ */
static void s626_set_dac(struct comedi_device *dev, uint16_t chan, static void s626_set_dac(struct comedi_device *dev, uint16_t chan,
unsigned short dacdata) int16_t dacdata)
{ {
struct s626_private *devpriv = dev->private; struct s626_private *devpriv = dev->private;
uint16_t signmask; uint16_t signmask;