2019-02-21 17:59:45

by Gustavo A. R. Silva

Subject: [PATCH] regulator: da9063: Use struct_size() in devm_kzalloc()

One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct foo {
int stuff;
struct boo entry[];
};

size = sizeof(struct foo) + count * sizeof(struct boo);
instance = alloc(size, GFP_KERNEL)

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

instance = alloc(struct_size(instance, entry, count), GFP_KERNEL)

Notice that, in this case, variable size is not necessary, hence it is
removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
drivers/regulator/da9063-regulator.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/regulator/da9063-regulator.c b/drivers/regulator/da9063-regulator.c
index a83bbd3dbc37..2b0c7a85306a 100644
--- a/drivers/regulator/da9063-regulator.c
+++ b/drivers/regulator/da9063-regulator.c
@@ -739,7 +739,6 @@ static int da9063_regulator_probe(struct platform_device *pdev)
struct regulator_config config;
bool bcores_merged, bmem_bio_merged;
int id, irq, n, n_regulators, ret, val;
- size_t size;

regl_pdata = da9063_pdata ? da9063_pdata->regulators_pdata : NULL;

@@ -784,9 +783,8 @@ static int da9063_regulator_probe(struct platform_device *pdev)
n_regulators--; /* remove BMEM_BIO_MERGED */

/* Allocate memory required by usable regulators */
- size = sizeof(struct da9063_regulators) +
- n_regulators * sizeof(struct da9063_regulator);
- regulators = devm_kzalloc(&pdev->dev, size, GFP_KERNEL);
+ regulators = devm_kzalloc(&pdev->dev, struct_size(regulators,
+ regulator, n_regulators), GFP_KERNEL);
if (!regulators)
return -ENOMEM;

--
2.20.1

2019-02-25 13:13:45

by Steve Twiss

Subject: RE: [PATCH] regulator: da9063: Use struct_size() in devm_kzalloc()

Hi Gustavo,

On 21 February 2019 17:57, Gustavo A. R. Silva wrote:

> Subject: [PATCH] regulator: da9063: Use struct_size() in devm_kzalloc()
>
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
>
> struct foo {
> int stuff;
> struct boo entry[];
> };
>
> size = sizeof(struct foo) + count * sizeof(struct boo);
> instance = alloc(size, GFP_KERNEL)
>
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:

Acked-by: Steve Twiss <[email protected]>

Thanks,

Regards,
Steve