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staging: comedi: ni_mio_common: Use insn->n in ni_calib_insn_write()

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The `insn_write` handler for the calibration subdevice
(`ni_calib_insn_write()`) currently ignores `insn->n` (the number of
samples to write) and assumes a single sample is to be written, but
`insn->n` could be 0, meaning no samples should be written, in which
case `data[0]` is invalid.

Change `ni_calib_insn_write()` to only write to the calibration device
if `insn->n > 0`.  There isn't much point writing all the values when
`insn->n > 1`, so just write the last one (`data[insn->n - 1]`).

Also follow the usual Comedi convention and return `insn->n` from the
handler to indicate success (although any non-negative return value will
do as far as the Comedi core is concerned).

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott 2019-03-19 16:54:41 +00:00 committed by Greg Kroah-Hartman
parent b8585eb51e
commit fe57d1e113
1 changed files with 6 additions and 2 deletions
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8
drivers/staging/comedi/drivers/ni_mio_common.c
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@ -4394,9 +4394,13 @@ static int ni_calib_insn_write(struct comedi_device *dev,
struct comedi_insn *insn, struct comedi_insn *insn,
unsigned int *data) unsigned int *data)
{ {
ni_write_caldac(dev, CR_CHAN(insn->chanspec), data[0]); if (insn->n) {
/* only bother writing the last sample to the channel */
ni_write_caldac(dev, CR_CHAN(insn->chanspec),
data[insn->n - 1]);
}
return 1; return insn->n;
} }
static int ni_calib_insn_read(struct comedi_device *dev, static int ni_calib_insn_read(struct comedi_device *dev,