[PATCH] rapidio/rio_mport_cdev: use struct_size() helper

[Gustavo A. R. Silva]

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 rio_switch {
	...
        struct rio_dev *nextdev[0];
};

Make use of the struct_size() helper instead of an open-coded version
in order to avoid any potential type mistakes.

So, replace the following form:

(RIO_GET_TOTAL_PORTS(swpinfo) * sizeof(rswitch->nextdev[0])) + sizeof(*rswitch)

with:

struct_size(rswitch, nextdev, RIO_GET_TOTAL_PORTS(swpinfo))

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
---
 drivers/rapidio/devices/rio_mport_cdev.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/rapidio/devices/rio_mport_cdev.c b/drivers/rapidio/devices/rio_mport_cdev.c
index 8155f59ece38..2787d2b7694d 100644
--- a/drivers/rapidio/devices/rio_mport_cdev.c
+++ b/drivers/rapidio/devices/rio_mport_cdev.c
@@ -1708,8 +1708,8 @@ static int rio_mport_add_riodev(struct mport_cdev_priv *priv,
 	if (rval & RIO_PEF_SWITCH) {
 		rio_mport_read_config_32(mport, destid, hopcount,
 					 RIO_SWP_INFO_CAR, &swpinfo);
-		size += (RIO_GET_TOTAL_PORTS(swpinfo) *
-			 sizeof(rswitch->nextdev[0])) + sizeof(*rswitch);
+		size += struct_size(rswitch, nextdev,
+				    RIO_GET_TOTAL_PORTS(swpinfo));
 	}
 
 	rdev = kzalloc(size, GFP_KERNEL);
-- 
2.23.0