Sorry for the very belated reply on this. I'm assuming that this was
already accepted, but I've been working with this patch for a bit. This
fixes the problems I raised in any case.
Reviewed-by: Spencer E Olson <olso...@umich.edu>
On Wed, 2016-07-20 at 17:07 +0100, Ian Abbott wrote:
> On 20/07/16 16:55, Hartley Sweeten wrote:
> > On Tuesday, July 19, 2016 4:18 AM, Ian Abbott wrote:
> >> Commit ebb657babfa9 ("staging: comedi: ni_mio_common: clarify the
> >> cmd->start_arg validation and use") introduced a backwards compatibility
> >> issue in the use of asynchronous commands on the AO subdevice when
> >> `start_src` is `TRIG_EXT`. Valid values for `start_src` are `TRIG_INT`
> >> (for internal, software trigger), and `TRIG_EXT` (for external trigger).
> >> When set to `TRIG_EXT`. In both cases, the driver relies on an
> >> internal, software trigger to set things up (allowing the user
> >> application to write sufficient samples to the data buffer before the
> >> trigger), so it acts as a software "pre-trigger" in the `TRIG_EXT` case.
> >> The software trigger is handled by `ni_ao_inttrig()`.
> >>
> >> Prior to the above change, when `start_src` was `TRIG_INT`, `start_arg`
> >> was required to be 0, and `ni_ao_inttrig()` checked that the software
> >> trigger number was also 0. After the above change, when `start_src` was
> >> `TRIG_INT`, any value was allowed for `start_arg`, and `ni_ao_inttrig()`
> >> checked that the software trigger number matched this `start_arg` value.
> >> The backwards compatibility issue is that the internal trigger number
> >> now has to match `start_arg` when `start_src` is `TRIG_EXT` when it
> >> previously had to be 0.
> >>
> >> Fix the backwards compatibility issue in `ni_ao_inttrig()` by always
> >> allowing software trigger number 0 when `start_src` is something other
> >> than `TRIG_INT`.
> >>
> >> Thanks to Spencer Olson for reporting the issue.
> >>
> >> Signed-off-by: Ian Abbott <abbo...@mev.co.uk>
> >> Reported-by: Spencer Olson <olso...@umich.edu>
> >> Fixes: ebb657babfa9 ("staging: comedi: ni_mio_common: clarify the
> >> cmd->start_arg validation and use")
> >> ---
> >> drivers/staging/comedi/drivers/ni_mio_common.c | 10 +++++++++-
> >> 1 file changed, 9 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/staging/comedi/drivers/ni_mio_common.c
> >> b/drivers/staging/comedi/drivers/ni_mio_common.c
> >> index 8dabb19..9f4036f 100644
> >> --- a/drivers/staging/comedi/drivers/ni_mio_common.c
> >> +++ b/drivers/staging/comedi/drivers/ni_mio_common.c
> >> @@ -2772,7 +2772,15 @@ static int ni_ao_inttrig(struct comedi_device *dev,
> >> int i;
> >> static const int timeout = 1000;
> >>
> >> - if (trig_num != cmd->start_arg)
> >> + /*
> >> + * Require trig_num == cmd->start_arg when cmd->start_src == TRIG_INT.
> >> + * For backwards compatibility, also allow trig_num == 0 when
> >> + * cmd->start_src != TRIG_INT (i.e. when cmd->start_src == TRIG_EXT);
> >> + * in that case, the internal trigger is being used as a pre-trigger
> >> + * before the external trigger.
> >> + */
> >> + if (!(trig_num == cmd->start_arg ||
> >> + (trig_num == 0 && cmd->start_src != TRIG_INT)))
> >> return -EINVAL;
> >
> > Ian,
> >
> > I think this test is a bit clearer:
> >
> > + /*
> > + * Require trig_num == cmd->start_arg when cmd->start_src == TRIG_INT.
> > + * For backwards compatibility, any trig_num is valid when
> > + * cmd->start_src != TRIG_INT (i.e. when cmd->start_src == TRIG_EXT);
> > + * in that case, the internal trigger is being used as a pre-trigger
> > + * before the external trigger.
> > + */
> > + if (cmd->start_src == TRIG_INT && trig_num != cmd->start_arg)
> > return -EINVAL;
>
> True, but I restricted it to only accept trig_num values that have been
> valid in the past.
>
> >
> > But, either way:
> >
> > Reviewed-by: H Hartley Sweeten <hswee...@visionengravers.com>
> >
> > Thanks!
> >
>
> Thanks for the review.
>
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