[PATCH] regulator: da9062: Use struct_size() in devm_kzalloc()

[PATCH] regulator: da9062: 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/da9062-regulator.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/regulator/da9062-regulator.c b/drivers/regulator/da9062-regulator.c
index 4c5d6ad853f8..b064d8a19d4c 100644
--- a/drivers/regulator/da9062-regulator.c
+++ b/drivers/regulator/da9062-regulator.c
@@ -992,7 +992,6 @@ static int da9062_regulator_probe(struct platform_device *pdev)
 	struct regulator_config config = { };
 	const struct da9062_regulator_info *rinfo;
 	int irq, n, ret;
-	size_t size;
 	int max_regulators;
 
 	switch (chip->chip_type) {
@@ -1010,9 +1009,8 @@ static int da9062_regulator_probe(struct platform_device *pdev)
 	}
 
 	/* Allocate memory required by usable regulators */
-	size = sizeof(struct da9062_regulators) +
-		max_regulators * sizeof(struct da9062_regulator);
-	regulators = devm_kzalloc(&pdev->dev, size, GFP_KERNEL);
+	regulators = devm_kzalloc(&pdev->dev, struct_size(regulators, regulator,
+				  max_regulators), GFP_KERNEL);
 	if (!regulators)
 		return -ENOMEM;
 
-- 
2.20.1

RE: [PATCH] regulator: da9062: Use struct_size() in devm_kzalloc()

[Steve Twiss]

Hi Gustavo,

On 23 February 2019 01:55, Gustavo A. R. Silva wrote:

> Subject: [PATCH] regulator: da9062: 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

> 
> 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/da9062-regulator.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/regulator/da9062-regulator.c b/drivers/regulator/da9062-
> regulator.c
> index 4c5d6ad853f8..b064d8a19d4c 100644
> --- a/drivers/regulator/da9062-regulator.c
> +++ b/drivers/regulator/da9062-regulator.c
> @@ -992,7 +992,6 @@ static int da9062_regulator_probe(struct platform_device
> *pdev)
>  	struct regulator_config config = { };
>  	const struct da9062_regulator_info *rinfo;
>  	int irq, n, ret;
> -	size_t size;
>  	int max_regulators;
> 
>  	switch (chip->chip_type) {
> @@ -1010,9 +1009,8 @@ static int da9062_regulator_probe(struct
> platform_device *pdev)
>  	}
> 
>  	/* Allocate memory required by usable regulators */
> -	size = sizeof(struct da9062_regulators) +
> -		max_regulators * sizeof(struct da9062_regulator);
> -	regulators = devm_kzalloc(&pdev->dev, size, GFP_KERNEL);
> +	regulators = devm_kzalloc(&pdev->dev, struct_size(regulators, regulator,
> +				  max_regulators), GFP_KERNEL);
>  	if (!regulators)
>  		return -ENOMEM;
> 
> --
> 2.20.1