Re: [RFT PATCH v3 10/10] iio: Don't silently expect attribute types

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Mon, Oct 03, 2022 at 12:02:56PM +0300, Matti Vaittinen wrote:
> On 10/3/22 11:58, Matti Vaittinen wrote:
> > On 10/3/22 11:43, Andy Shevchenko wrote:
> > > On Mon, Oct 03, 2022 at 11:13:53AM +0300, Matti Vaittinen wrote:

...

> > > > +            attr[ARRAY_SIZE(iio_buffer_attrs) + i] =
> > > > +                (struct attribute *)&id_attr->dev_attr.attr;
> > > 
> > > ...and explicit casting here. Isn't attr is already of a struct
> > > attribute?
> > 
> > I am glad you asked :)
> > This is one of the "things" I was not really happy about. Here we hide
> > the fact that our array is full of pointers to _const_ data. If we don't
> > cast the compiler points this out. Old code did the same thing but it
> > did this by just doing a memcpy for the pointers - which I personally
> > consider even worse as it gets really easy to miss this. The cast at
> > least hints there is something slightly "fishy" going on.
> > 
> > My "gut feeling" about the correct fix is we should check if some
> > attributes in the array (stored to the struct here) actually need to be
> > modified later (which I doubt). If I was keen on betting I'd bet we
> > could switch the struct definition to also contain pointers to const
> > attributes. I am afraid this would mean quite a few more changes to the
> > function signatures (changing struct attribute * to const struct
> > attribute *) here and there - and possibly also require some changes to
> > drivers. Thus I didn't even look at that option in the scope of this
> > fix. It should probably be a separate refactoring series. But yes - this
> > cast should catch attention as it did.
> > 
> 
> Actually, now that you pointed it out - do you think this would warrant a
> FIXME comment?

Makes sense to me, but I'm not a maintainer of IIO :-)

-- 
With Best Regards,
Andy Shevchenko