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staging: comedi: cb_pcidas64: Use insn->n in EEPROM insn_read handler

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The `insn_read` handler for the EEPROM subdevice (`eeprom_insn_read()`)
currently ignores `insn->n` (the number of samples to be read) and
assumes a single sample is to be read.  But `insn->n` could be 0,
meaning no samples should be read, in which case `data[0]` ought not to
be written.  (The comedi core at least ensures that `data[0]` exists,
but we should not rely on that.)

Follow the usual Comedi guidelines and interpret `insn->n` as the number
of samples to be read, but only read the EEPROM location once and make
`insn->n` copies, as we don't expect the contents of the EEPROM location
to change between readings.

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 2018-10-30 14:17:12 +00:00 committed by Greg Kroah-Hartman
parent 130151991d
commit b33fc68c26
1 changed files with 10 additions and 2 deletions
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12
drivers/staging/comedi/drivers/cb_pcidas64.c
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@ -3768,9 +3768,17 @@ static int eeprom_read_insn(struct comedi_device *dev,
struct comedi_subdevice *s,
struct comedi_insn *insn, unsigned int *data)
{
data[0] = read_eeprom(dev, CR_CHAN(insn->chanspec));
unsigned int val;
unsigned int i;
return 1;
if (insn->n) {
/* No point reading the same EEPROM location more than once. */
val = read_eeprom(dev, CR_CHAN(insn->chanspec));
for (i = 0; i < insn->n; i++)
data[i] = val;
}
return insn->n;
}
/* Allocate and initialize the subdevice structures. */