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

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Message-Id: <dd132142858d108814a36fc044431c4ae34ea3f8.1485514374.git.jslaby@suse.cz>
Date:   Fri, 27 Jan 2017 11:54:21 +0100
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Paul Burton <paul.burton@...tec.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 128/235] net: ti: cpmac: Fix compiler warning due to type confusion

From: Paul Burton <paul.burton@...tec.com>

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
warning:

  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@...tec.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 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);
 
-- 
2.11.0