linux-kernel - [PATCH] staging: mt7621-dma: Use struct_size() in devm

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Message-ID: <20190104213047.GA19391@embeddedor>
Date:   Fri, 4 Jan 2019 15:30:47 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>
Cc:     devel@...verdev.osuosl.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] staging: mt7621-dma: 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;
    void *entry[];
};

instance = devm_kzalloc(dev, sizeof(struct foo) + sizeof(void *) * count, 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/staging/mt7621-dma/ralink-gdma.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/mt7621-dma/ralink-gdma.c b/drivers/staging/mt7621-dma/ralink-gdma.c
index 792a63bd55d4..d78042eba6dd 100644
--- a/drivers/staging/mt7621-dma/ralink-gdma.c
+++ b/drivers/staging/mt7621-dma/ralink-gdma.c
@@ -821,9 +821,9 @@ static int gdma_dma_probe(struct platform_device *pdev)
 		return -EINVAL;
 	data = (struct gdma_data *) match->data;
 
-	dma_dev = devm_kzalloc(&pdev->dev, sizeof(*dma_dev) +
-			(sizeof(struct gdma_dmaengine_chan) * data->chancnt),
-			GFP_KERNEL);
+	dma_dev = devm_kzalloc(&pdev->dev,
+			       struct_size(dma_dev, chan, data->chancnt),
+			       GFP_KERNEL);
 	if (!dma_dev) {
 		dev_err(&pdev->dev, "alloc dma device failed\n");
 		return -EINVAL;
-- 
2.20.1