[PATCH][next] zd1211rw: use struct_size() helper

["Gustavo A. R. Silva" <gustavo@embeddedor.com>]

Make use of the struct_size() helper instead of an open-coded version
in order to avoid any potential type mistakes, in particular in the
context in which this code is being used.

So, replace code of the following form:

sizeof(struct usb_req_write_regs) + count * sizeof(struct reg_data)

with:

struct_size(req, reg_writes, count)

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/net/wireless/zydas/zd1211rw/zd_usb.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/wireless/zydas/zd1211rw/zd_usb.c b/drivers/net/wireless/zydas/zd1211rw/zd_usb.c
index c2cda3acd4af..a094d5b3383c 100644
--- a/drivers/net/wireless/zydas/zd1211rw/zd_usb.c
+++ b/drivers/net/wireless/zydas/zd1211rw/zd_usb.c
@@ -1917,8 +1917,7 @@ int zd_usb_iowrite16v_async(struct zd_usb *usb, const struct zd_ioreq16 *ioreqs,
 	if (!urb)
 		return -ENOMEM;
 
-	req_len = sizeof(struct usb_req_write_regs) +
-		  count * sizeof(struct reg_data);
+	req_len = struct_size(req, reg_writes, count);
 	req = kmalloc(req_len, GFP_KERNEL);
 	if (!req) {
 		r = -ENOMEM;
-- 
2.21.0