On Tuesday, October 30, 2018 7:17 AM, Ian Abbott wrote:
> 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 <[email protected]>
> ---
> drivers/staging/comedi/drivers/cb_pcidas64.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/staging/comedi/drivers/cb_pcidas64.c
> b/drivers/staging/comedi/drivers/cb_pcidas64.c
> index 44e5aaf8bae5..e1774e09a320 100644
> --- a/drivers/staging/comedi/drivers/cb_pcidas64.c
> +++ b/drivers/staging/comedi/drivers/cb_pcidas64.c
> @@ -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;
> }
Hi Ian,
I realize it's not the "normal" Comedi use, but with the EEPROM I would think
that if the user
wanted to read more than one sample they would expect to read a block of data
from the
EEPROM.
Maybe the EEPROM read should be something like:
+ if (insn->n) {
+ unsigned int address = CR_CHAN(insn->chanspec);
+ for (i = 0; i < insn->n; i++) {
+ val = read_eeprom(dev, address);
+ data[i] = val;
+ address++;
+ if (address >= s->n_chan)
+ address = 0;
+ }
+ }
Regards,
Hartley
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