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iommu: Use C99 flexible array in fwspec 

Although the 1-element array was a typical pre-C99 way to implement
variable-length structures, and indeed is a fundamental construct in the
APIs of certain other popular platforms, there's no good reason for it
here (and in particular the sizeof() trick is far too "clever" for its
own good). We can just as easily implement iommu_fwspec's preallocation
behaviour using a standard flexible array member, so let's make it look
the way most readers would expect.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Robin Murphy 2020-02-13 14:00:21 +00:00 committed by Joerg Roedel
parent f8788d86ab
commit 098accf2da
2 changed files with 9 additions and 8 deletions
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15
drivers/iommu/iommu.c
View File

@ -2405,7 +2405,8 @@ int iommu_fwspec_init(struct device *dev, struct fwnode_handle *iommu_fwnode,
if (fwspec)
return ops == fwspec->ops ? 0 : -EINVAL;
fwspec = kzalloc(sizeof(*fwspec), GFP_KERNEL);
/* Preallocate for the overwhelmingly common case of 1 ID */
fwspec = kzalloc(struct_size(fwspec, ids, 1), GFP_KERNEL);
if (!fwspec)
return -ENOMEM;
@ -2432,15 +2433,15 @@ EXPORT_SYMBOL_GPL(iommu_fwspec_free);
int iommu_fwspec_add_ids(struct device *dev, u32 *ids, int num_ids)
{
struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
size_t size;
int i;
int i, new_num;
if (!fwspec)
return -EINVAL;
size = offsetof(struct iommu_fwspec, ids[fwspec->num_ids + num_ids]);
if (size > sizeof(*fwspec)) {
fwspec = krealloc(fwspec, size, GFP_KERNEL);
new_num = fwspec->num_ids + num_ids;
if (new_num > 1) {
fwspec = krealloc(fwspec, struct_size(fwspec, ids, new_num),
GFP_KERNEL);
if (!fwspec)
return -ENOMEM;
@ -2450,7 +2451,7 @@ int iommu_fwspec_add_ids(struct device *dev, u32 *ids, int num_ids)
for (i = 0; i < num_ids; i++)
fwspec->ids[fwspec->num_ids + i] = ids[i];
fwspec->num_ids += num_ids;
fwspec->num_ids = new_num;
return 0;
}
EXPORT_SYMBOL_GPL(iommu_fwspec_add_ids);

2
include/linux/iommu.h
View File

@ -592,7 +592,7 @@ struct iommu_fwspec {
u32 flags;
u32 num_pasid_bits;
unsigned int num_ids;
u32 ids[1];
u32 ids[];
};
/* ATS is supported */