[PATCH][next] rapidio: Use struct_size() helper

[Gustavo A. R. Silva]

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

Also, while there, use the preferred form for passing a size of a struct.
The alternative form where struct name is spelled out hurts readability
and introduces an opportunity for a bug when the pointer variable type is
changed but the corresponding sizeof that is passed as argument is not.

This issue was found with the help of Coccinelle and, audited and fixed
manually.

Addresses-KSPP-ID: https://github.com/KSPP/linux/issues/83
Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
---
 drivers/rapidio/rio-scan.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/rapidio/rio-scan.c b/drivers/rapidio/rio-scan.c
index eb8ed28533f8..19b0c33f4a62 100644
--- a/drivers/rapidio/rio-scan.c
+++ b/drivers/rapidio/rio-scan.c
@@ -330,7 +330,7 @@ static struct rio_dev *rio_setup_device(struct rio_net *net,
 	size_t size;
 	u32 swpinfo = 0;
 
-	size = sizeof(struct rio_dev);
+	size = sizeof(*rdev);
 	if (rio_mport_read_config_32(port, destid, hopcount,
 				     RIO_PEF_CAR, &result))
 		return NULL;
@@ -338,10 +338,8 @@ static struct rio_dev *rio_setup_device(struct rio_net *net,
 	if (result & (RIO_PEF_SWITCH | RIO_PEF_MULTIPORT)) {
 		rio_mport_read_config_32(port, destid, hopcount,
 					 RIO_SWP_INFO_CAR, &swpinfo);
-		if (result & RIO_PEF_SWITCH) {
-			size += (RIO_GET_TOTAL_PORTS(swpinfo) *
-				sizeof(rswitch->nextdev[0])) + sizeof(*rswitch);
-		}
+		if (result & RIO_PEF_SWITCH)
+			size += struct_size(rswitch, nextdev, RIO_GET_TOTAL_PORTS(swpinfo));
 	}
 
 	rdev = kzalloc(size, GFP_KERNEL);
-- 
2.27.0