Re: [PATCH][V2] iio: st_accel: fix iio_triggered_buffer_{pre,post}enable positions

["Ardelean, Alexandru" <alexandru.Ardelean@analog.com>]

On Mon, 2019-06-10 at 21:20 +0000, Denis CIOCCA wrote:
> [External]
> 
> 
> Hi Jonathan, Alexandru,
> 
> I agree with you about the predisable but I am not convinced regarding the postenable.
> Few modifications have been made on magn driver and never replicated on accel. I think should be done in the same way
> magn is implemented.
> During postenable kmalloc should be called first because iio_triggered_buffer_postenable function it enables irq and
> if an interrupt arrives before the memory is allocated (wrong interrupt or failure of switching sensor off from
> previous disable) it could generate a null pointer exception. Make sense to you?

I got the gist of it.
And it makes sense.
I'll update the patch.

[on a related topic]
One curious/question: would it make sense to move the allocation of `buffer_data` somewhere in
`drivers/iio/common/st_sensor/st_sensors_buffer.c` ?
I was looking for `buffer_data` [and how it's used], and notice this.

Thanks
Alex

> 
> Thanks & Br,
> Denis
> 
> 
> 
> -----Original Message-----
> From: Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
> Sent: Saturday, June 8, 2019 7:10 AM
> To: Alexandru Ardelean <alexandru.ardelean@analog.com>
> Cc: linux-iio@vger.kernel.org; Denis CIOCCA <denis.ciocca@st.com>; Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
> Subject: Re: [PATCH][V2] iio: st_accel: fix iio_triggered_buffer_{pre,post}enable positions
> 
> On Wed, 29 May 2019 16:58:48 +0300
> Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:
> 
> > The iio_triggered_buffer_{predisable,postenable} functions
> > attach/detach the poll functions.
> > 
> > For the predisable hook, the disable code should occur before
> > detaching the poll func, and for the postenable hook, the poll func
> > should be attached before the enable code.
> > 
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> I think this is fine, but I'd like an ack from Lorenzo / Denis.
> 
> Note to those who have missed the background on this, the aim is to both tidy up drivers, but long term to allow for
> simpler reworking of the core by ensuring consistency of ordering and what is done in each of these hooks.
> 
> Thanks,
> 
> Jonathan
> 
> > ---
> > Changelog v1 -> v2:
> > * record the first error in st_accel_buffer_predisable() and return
> > that
> > 
> >  drivers/iio/accel/st_accel_buffer.c | 21 ++++++++++++---------
> >  1 file changed, 12 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/iio/accel/st_accel_buffer.c
> > b/drivers/iio/accel/st_accel_buffer.c
> > index 7fddc137e91e..711ecd9bc898 100644
> > --- a/drivers/iio/accel/st_accel_buffer.c
> > +++ b/drivers/iio/accel/st_accel_buffer.c
> > @@ -40,6 +40,10 @@ static int st_accel_buffer_postenable(struct iio_dev *indio_dev)
> >       int err;
> >       struct st_sensor_data *adata = iio_priv(indio_dev);
> > 
> > +     err = iio_triggered_buffer_postenable(indio_dev);
> > +     if (err < 0)
> > +             return err;
> > +
> >       adata->buffer_data = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
> >       if (adata->buffer_data == NULL) {
> >               err = -ENOMEM;
> > @@ -51,34 +55,33 @@ static int st_accel_buffer_postenable(struct iio_dev *indio_dev)
> >       if (err < 0)
> >               goto st_accel_buffer_postenable_error;
> > 
> > -     err = iio_triggered_buffer_postenable(indio_dev);
> > -     if (err < 0)
> > -             goto st_accel_buffer_postenable_error;
> > -
> >       return err;
> > 
> >  st_accel_buffer_postenable_error:
> >       kfree(adata->buffer_data);
> >  allocate_memory_error:
> > +     iio_triggered_buffer_predisable(indio_dev);
> >       return err;
> >  }
> > 
> >  static int st_accel_buffer_predisable(struct iio_dev *indio_dev)  {
> > -     int err;
> > +     int err, err2;
> >       struct st_sensor_data *adata = iio_priv(indio_dev);
> > 
> > -     err = iio_triggered_buffer_predisable(indio_dev);
> > -     if (err < 0)
> > -             goto st_accel_buffer_predisable_error;
> > -
> >       err = st_sensors_set_axis_enable(indio_dev, ST_SENSORS_ENABLE_ALL_AXIS);
> >       if (err < 0)
> >               goto st_accel_buffer_predisable_error;
> > 
> >       err = st_sensors_set_enable(indio_dev, false);
> > +     if (err < 0)
> > +             goto st_accel_buffer_predisable_error;
> > 
> >  st_accel_buffer_predisable_error:
> > +     err2 = iio_triggered_buffer_predisable(indio_dev);
> > +     if (!err)
> > +             err = err2;
> > +
> >       kfree(adata->buffer_data);
> >       return err;
> >  }