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

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

[Gustavo A. R. Silva]

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 <gustavo@embeddedor.com>
---
 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

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

[Steve Twiss]

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 <stwiss.opensource@diasemi.com>

Thanks,

Regards,
Steve