linux-kernel - [PATCH] phy: samsung: Use struct_size() in devm

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Message-ID: <20190605200002.GA18640@embeddedor>
Date:   Wed, 5 Jun 2019 15:00:02 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Kamil Debski <kamil@...as.org>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Kishon Vijay Abraham I <kishon@...com>
Cc:     linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] phy: samsung: 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 samsung_usb2_phy_driver {
	...
        struct samsung_usb2_phy_instance instances[0];
};

instance = devm_kzalloc(dev, sizeof(struct samsung_usb2_phy_driver) + count *
			sizeof(struct samsung_usb2_phy_instance), 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, instances, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/phy/samsung/phy-samsung-usb2.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/phy/samsung/phy-samsung-usb2.c b/drivers/phy/samsung/phy-samsung-usb2.c
index ea818866985a..4616ec829900 100644
--- a/drivers/phy/samsung/phy-samsung-usb2.c
+++ b/drivers/phy/samsung/phy-samsung-usb2.c
@@ -159,9 +159,8 @@ static int samsung_usb2_phy_probe(struct platform_device *pdev)
 	if (!cfg)
 		return -EINVAL;
 
-	drv = devm_kzalloc(dev, sizeof(struct samsung_usb2_phy_driver) +
-		cfg->num_phys * sizeof(struct samsung_usb2_phy_instance),
-								GFP_KERNEL);
+	drv = devm_kzalloc(dev, struct_size(drv, instances, cfg->num_phys),
+			   GFP_KERNEL);
 	if (!drv)
 		return -ENOMEM;
 
-- 
2.21.0