Re: [PATCH 01/32] iio: accel: kxsd9: Fix alignment of local buffer.

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 7 Jun 2020 19:05:15 +0300
Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> On Sun, Jun 7, 2020 at 6:57 PM Jonathan Cameron <jic23@kernel.org> wrote:
> >
> > From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> >
> > iio_push_to_buffers_with_timestamp assumes 8 byte alignment which
> > is not guaranteed by an array of smaller elements.
> >
> > Note that whilst in this particular case the alignment forcing
> > of the ts element is not strictly necessary it acts as good
> > documentation.  
> 
> ...
> 
> > +       struct {
> > +               __be16 chan[4];
> > +               s64 ts __aligned(8);
> > +       } hw_values;  
> 
> I'm not sure what __aligned can do better here? It's naturally will be
> 8 alignment (struct itself due to s64 followed by 4*__be16).
> 
Mainly I put it in all cases even when not needed to ensure that
copy and paste versions keep the alignment statement.  Here I agree
it does nothing but if someone adds another channel to a driver
they might miss that they also need to then add the __aligned(8)
for the timestamp.

Jonathan