linux-kernel - [PATCH 2/2] mfd: sm501: Use struct_size() in devm

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Message-ID: <4e25a7933cc9876b24fa3322637a22df7475bc40.1548175934.git.gustavo@embeddedor.com>
Date:   Tue, 22 Jan 2019 10:58:20 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Lee Jones <lee.jones@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH 2/2] mfd: sm501: 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[];
};

instance = devm_kzalloc(dev, sizeof(struct foo) + count * sizeof(struct boo), 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, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/mfd/sm501.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/mfd/sm501.c b/drivers/mfd/sm501.c
index e0173bf4b0dc..d217debf382e 100644
--- a/drivers/mfd/sm501.c
+++ b/drivers/mfd/sm501.c
@@ -1142,8 +1142,7 @@ static int sm501_register_gpio_i2c_instance(struct sm501_devdata *sm,
 		return -ENOMEM;
 
 	/* Create a gpiod lookup using gpiochip-local offsets */
-	lookup = devm_kzalloc(&pdev->dev,
-			      sizeof(*lookup) + 3 * sizeof(struct gpiod_lookup),
+	lookup = devm_kzalloc(&pdev->dev, struct_size(lookup, table, 3),
 			      GFP_KERNEL);
 	if (!lookup)
 		return -ENOMEM;
-- 
2.20.1