[PATCH 3.12 128/235] net: ti: cpmac: Fix compiler warning due to type confusion

From: Jiri Slaby
Date: Fri Jan 27 2017 - 06:42:23 EST

From: Paul Burton <paul.burton@xxxxxxxxxx>

3.12-stable review patch. If anyone has any objections, please let me know.


commit 2f5281ba2a8feaf6f0aee93356f350855bb530fc upstream.

cpmac_start_xmit() used the max() macro on skb->len (an unsigned int)
and ETH_ZLEN (a signed int literal). This led to the following compiler

In file included from include/linux/list.h:8:0,
from include/linux/module.h:9,
from drivers/net/ethernet/ti/cpmac.c:19:
drivers/net/ethernet/ti/cpmac.c: In function 'cpmac_start_xmit':
include/linux/kernel.h:748:17: warning: comparison of distinct pointer
types lacks a cast
(void) (&_max1 == &_max2); \
drivers/net/ethernet/ti/cpmac.c:560:8: note: in expansion of macro 'max'
len = max(skb->len, ETH_ZLEN);

On top of this, it assigned the result of the max() macro to a signed
integer whilst all further uses of it result in it being cast to varying
widths of unsigned integer.

Fix this up by using max_t to ensure the comparison is performed as
unsigned integers, and for consistency change the type of the len
variable to unsigned int.

Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
drivers/net/ethernet/ti/cpmac.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/ti/cpmac.c b/drivers/net/ethernet/ti/cpmac.c
index 2dc16b6efaf0..97f3e626b535 100644
--- a/drivers/net/ethernet/ti/cpmac.c
+++ b/drivers/net/ethernet/ti/cpmac.c
@@ -557,7 +557,8 @@ fatal_error:

static int cpmac_start_xmit(struct sk_buff *skb, struct net_device *dev)
- int queue, len;
+ int queue;
+ unsigned int len;
struct cpmac_desc *desc;
struct cpmac_priv *priv = netdev_priv(dev);

@@ -567,7 +568,7 @@ static int cpmac_start_xmit(struct sk_buff *skb, struct net_device *dev)
if (unlikely(skb_padto(skb, ETH_ZLEN)))
return NETDEV_TX_OK;

- len = max(skb->len, ETH_ZLEN);
+ len = max_t(unsigned int, skb->len, ETH_ZLEN);
queue = skb_get_queue_mapping(skb);
netif_stop_subqueue(dev, queue);