Hi Will,
On Thu, Jul 16, 2015 at 11:23:26AM +0100, Will Deacon wrote:
> On Thu, Jul 16, 2015 at 09:30:43AM +0100, Joerg Roedel wrote:
> > +struct of_phandle_args *of_alloc_phandle_args(int size)
> > +{
> > + struct of_phandle_args *args;
> > + int e = max(0, size - MAX_PHANDLE_ARGS);
> > +
> > + args = kzalloc(sizeof(struct of_phandle_args) + e * sizeof(uint32_t),
> > + GFP_KERNEL);
>
> Should you also update args->args_count to reflect the extended array?
The args_count member just tells us how many of the array elements are
used and not how many there are. So it doesn't need to be updated here.
> That said, extending the fixed-size array member like this feels a bit
> fragile. Does GCC not complain about out-of-bounds accesses if you
> statically address args->args[MAX_PHANDLE_ARGS]? Admittedly, I can't
> think *why* this would be break (things like additional padding will be
> harmless), but I'm not intimate with the C standard.
Yeah, I agree, it is not the best possible solution. But this way I
don't need to update all callers, and thus it works better with our
development model.
But I am open for suggestions on how to solve this problem better. In
fact, my main motivation in sending this was to get the discussion about
an upstreamable solution started :)
Lets see what the device-tree maintainers have to say.
> I guess the more worrying possibility is if somebody adds a new member to
> the end of of_phandle_args.
I should probably add a comment there.
Joerg
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