[PATCH] Input: gpio_keys_polled - use struct_size() in devm_kzalloc()

From: Gustavo A. R. Silva
Date: Wed Jun 19 2019 - 10:32:07 EST

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 gpio_keys_polled_dev {
struct gpio_keys_button_data data[0];

size = sizeof(struct gpio_keys_polled_dev) + count * sizeof(struct gpio_keys_button_data);
instance = devm_kzalloc(dev, size, GFP_KERNEL);

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

instance = devm_kzalloc(dev, struct_size(instance, data, 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@xxxxxxxxxxxxxx>
drivers/input/keyboard/gpio_keys_polled.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/input/keyboard/gpio_keys_polled.c b/drivers/input/keyboard/gpio_keys_polled.c
index edc7262103b9..c4087be0c2e0 100644
--- a/drivers/input/keyboard/gpio_keys_polled.c
+++ b/drivers/input/keyboard/gpio_keys_polled.c
@@ -235,7 +235,6 @@ static int gpio_keys_polled_probe(struct platform_device *pdev)
struct gpio_keys_polled_dev *bdev;
struct input_polled_dev *poll_dev;
struct input_dev *input;
- size_t size;
int error;
int i;

@@ -250,9 +249,8 @@ static int gpio_keys_polled_probe(struct platform_device *pdev)
return -EINVAL;

- size = sizeof(struct gpio_keys_polled_dev) +
- pdata->nbuttons * sizeof(struct gpio_keys_button_data);
- bdev = devm_kzalloc(dev, size, GFP_KERNEL);
+ bdev = devm_kzalloc(dev, struct_size(bdev, data, pdata->nbuttons),
if (!bdev) {
dev_err(dev, "no memory for private data\n");
return -ENOMEM;