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@embeddedor.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190807161312.GA26835@embeddedor

diff --git a/drivers/video/fbdev/mmp/core.c b/drivers/video/fbdev/mmp/core.c
index 0ffc1b7..1541272 100644 (file)
--- 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;