Hi, all.
+struct iommu_fwspec {
+ /* this device's IOMMU */
+ struct device *iommu_dev;
+ /* IOMMU driver private data for this device */
+ void *iommu_priv;
+ /* number of associated device IDs */
+ unsigned int num_ids;
+ /* IDs which this device may present to the IOMMU */
+ uint32_t ids[1];
+};
Note that you abuse xrealloc_flex_struct() when using it with such
a type: The last field is _not_ a flexible array member. Compilers
might legitimately warn if they can prove that you access
p->ids[1] anywhere, despite you (presumably) having allocated
enough
space. (I haven't been able to think of a way for the macro to
actually detect and hence refuse such wrong uses.)
Indeed, you are right. I am in doubt, whether to retain ported from
Linux code (ids[1])
and mention about such abuse or change it to deal with real
flexible
array member (ids[]). Any thoughts?
I'm of the strong opinion that you should switch to [] (or at
least [0]) notation.
I got it. Well, will switch to ids[] if there are no objections.
I suspect the rationale to use 1 rather than 0 is to avoid the
re-allocation in
the common case where a device has a single ID.
I would like to retain the similar behavior. The ids[1] is probably
the most
pretty way to do it.
Another solution would to use xmalloc_bytes() for the initial
allocation of
xmalloc_bytes().
Why not use xmalloc_flex_<whatever>() on the first allocation, too?
Hmm, why not? Looks like the xmalloc_flex_struct fits here.
The first allocation would be:
fwspec = xmalloc_flex_struct(struct iommu_fwspec, ids, 1);
The re-allocation for the devices with single ID would do effectively
nothing (assuming that _xrealloc will recognize that size is the same):
fwspec = xrealloc_flex_struct(fwspec, ids, fwspec->num_ids + num_ids);
Julien, what do you think?
I am happy with that. The first allocation would need a comment on top
explaining the reason of the "1".
Sure, will add.
--
Regards,
Oleksandr Tyshchenko
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