[PATCH] Input: gpio_keys - 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 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 <gust...@embeddedor.com>
---
 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