linux-kernel - [PATCH] video: fbdev/mmp/core: Use struct

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Message-ID: <20190807161312.GA26835@embeddedor>
Date:   Wed, 7 Aug 2019 11:13:12 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] video: fbdev/mmp/core: Use struct_size() in 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 mmp_path {
	...
        struct mmp_overlay overlays[0];
};

size = sizeof(struct mmp_path) + count * sizeof(struct mmp_overlay);
instance = kzalloc(size, GFP_KERNEL)

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

instance = kzalloc(struct_size(instance, overlays, 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@...eddedor.com>
---
 drivers/video/fbdev/mmp/core.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/video/fbdev/mmp/core.c b/drivers/video/fbdev/mmp/core.c
index 0ffc1b7b7052..154127256a2c 100644
--- a/drivers/video/fbdev/mmp/core.c
+++ b/drivers/video/fbdev/mmp/core.c
@@ -153,13 +153,11 @@ EXPORT_SYMBOL_GPL(mmp_get_path);
 struct mmp_path *mmp_register_path(struct mmp_path_info *info)
 {
 	int i;
-	size_t size;
 	struct mmp_path *path = NULL;
 	struct mmp_panel *panel;
 
-	size = sizeof(struct mmp_path)
-		+ sizeof(struct mmp_overlay) * info->overlay_num;
-	path = kzalloc(size, GFP_KERNEL);
+	path = kzalloc(struct_size(path, overlays, info->overlay_num),
+		       GFP_KERNEL);
 	if (!path)
 		return NULL;
 
-- 
2.22.0