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_drvdata {
...
struct gpio_button_data data[0];
};
size = sizeof(struct gpio_keys_drvdata) + count * sizeof(struct gpio_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.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/drivers/input/keyboard/gpio_keys.c b/drivers/input/keyboard/gpio_keys.c
index 6cd199e8a370..c186c2552b04 100644
--- a/drivers/input/keyboard/gpio_keys.c
+++ b/drivers/input/keyboard/gpio_keys.c
@@ -774,7 +774,6 @@ static int gpio_keys_probe(struct platform_device *pdev)
struct fwnode_handle *child = NULL;
struct gpio_keys_drvdata *ddata;
struct input_dev *input;
- size_t size;
int i, error;
int wakeup = 0;
@@ -784,9 +783,8 @@ static int gpio_keys_probe(struct platform_device *pdev)
return PTR_ERR(pdata);
}
- size = sizeof(struct gpio_keys_drvdata) +
- pdata->nbuttons * sizeof(struct gpio_button_data);
- ddata = devm_kzalloc(dev, size, GFP_KERNEL);
+ ddata = devm_kzalloc(dev, struct_size(ddata, data, pdata->nbuttons),
+ GFP_KERNEL);
if (!ddata) {
dev_err(dev, "failed to allocate state\n");
return -ENOMEM;
--
2.21.0
