Input: gpio_keys_polled - 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 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@embeddedor.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

diff --git a/drivers/input/keyboard/gpio_keys_polled.c b/drivers/input/keyboard/gpio_keys_polled.c
index edc7262103b9ac982f1dee130723849a5d6a275f..c4087be0c2e0fca5a531457b31348606c72af49a 100644 (file)
--- 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),
+                           GFP_KERNEL);
        if (!bdev) {
                dev_err(dev, "no memory for private data\n");
                return -ENOMEM;