linux-kernel - [PATCH net-next] hinic: avoid gcc -Wrestrict warning

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Date:   Tue, 23 Mar 2021 13:56:05 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Bin Luo <luobin9@...wei.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Arnd Bergmann <arnd@...db.de>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH net-next] hinic: avoid gcc -Wrestrict warning

From: Arnd Bergmann <arnd@...db.de>

With extra warnings enabled, gcc complains that snprintf should not
take the same buffer as source and destination:

drivers/net/ethernet/huawei/hinic/hinic_ethtool.c: In function 'hinic_set_settings_to_hw':
drivers/net/ethernet/huawei/hinic/hinic_ethtool.c:480:9: error: 'snprintf' argument 4 overlaps destination object 'set_link_str' [-Werror=restrict]
  480 |   err = snprintf(set_link_str, SET_LINK_STR_MAX_LEN,
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  481 |           "%sspeed %d ", set_link_str, speed);
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/huawei/hinic/hinic_ethtool.c:464:7: note: destination object referenced by 'restrict'-qualified argument 1 was declared here
  464 |  char set_link_str[SET_LINK_STR_MAX_LEN] = {0};

Rewrite this to remember the offset of the previous printf output
instead.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/net/ethernet/huawei/hinic/hinic_ethtool.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c b/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c
index c340d9acba80..74aefc8fc4d8 100644
--- a/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c
+++ b/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c
@@ -464,7 +464,7 @@ static int hinic_set_settings_to_hw(struct hinic_dev *nic_dev,
 	char set_link_str[SET_LINK_STR_MAX_LEN] = {0};
 	struct net_device *netdev = nic_dev->netdev;
 	enum nic_speed_level speed_level = 0;
-	int err;
+	int err, off;
 
 	err = snprintf(set_link_str, SET_LINK_STR_MAX_LEN, "%s",
 		       (set_settings & HILINK_LINK_SET_AUTONEG) ?
@@ -475,10 +475,11 @@ static int hinic_set_settings_to_hw(struct hinic_dev *nic_dev,
 		return -EFAULT;
 	}
 
+	off = err;
 	if (set_settings & HILINK_LINK_SET_SPEED) {
 		speed_level = hinic_ethtool_to_hw_speed_level(speed);
-		err = snprintf(set_link_str, SET_LINK_STR_MAX_LEN,
-			       "%sspeed %d ", set_link_str, speed);
+		err = snprintf(set_link_str + off, SET_LINK_STR_MAX_LEN - off,
+			       "speed %d ", speed);
 		if (err <= 0 || err >= SET_LINK_STR_MAX_LEN) {
 			netif_err(nic_dev, drv, netdev, "Failed to snprintf link speed, function return(%d) and dest_len(%d)\n",
 				  err, SET_LINK_STR_MAX_LEN);
-- 
2.29.2