[PATCH v2] net/mlx5: fix warning from uninitialized variable

[Stephen Hemminger <stephen@networkplumber.org>]

Gcc-16 detects use of uninitialized variable.
./drivers/net/mlx5/linux/mlx5_ethdev_os.c: In function ‘mlx5_link_update’:
../drivers/net/mlx5/linux/mlx5_ethdev_os.c:539:15: warning: ‘*(long unsigned int *)((char *)&dev_link + offsetof(struct rte_eth_link, <U38c0>))’ may be used uninitialized [-Wmaybe-uninitialized]
  539 |         ret = !!memcmp(&dev->data->dev_link, &dev_link,
      |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  540 |                        sizeof(struct rte_eth_link));
      |                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../drivers/net/mlx5/linux/mlx5_ethdev_os.c:515:29: note: ‘*(long unsigned int *)((char *)&dev_link + offsetof(struct rte_eth_link, <U38c0>))’ was declared here
  515 |         struct rte_eth_link dev_link;
      |

If the retry loop exits the code would do memcmp against uninitialized
stack value. Resolve by initializing to zero.

Bugzilla ID: 1823

Fixes: 1256805dd54d ("net/mlx5: move Linux-specific functions")
Fixes: cfee94752b8f ("net/mlx5: fix link status to use wait to complete")
Cc: stable@dpdk.org

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 drivers/net/mlx5/linux/mlx5_ethdev_os.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/mlx5/linux/mlx5_ethdev_os.c b/drivers/net/mlx5/linux/mlx5_ethdev_os.c
index 4d8fbed188..50997c187c 100644
--- a/drivers/net/mlx5/linux/mlx5_ethdev_os.c
+++ b/drivers/net/mlx5/linux/mlx5_ethdev_os.c
@@ -512,7 +512,7 @@ int
 mlx5_link_update(struct rte_eth_dev *dev, int wait_to_complete)
 {
 	int ret;
-	struct rte_eth_link dev_link;
+	struct rte_eth_link dev_link = { 0 };
 	time_t start_time = time(NULL);
 	int retry = MLX5_GET_LINK_STATUS_RETRY_COUNT;
 
@@ -2073,4 +2073,3 @@ int mlx5_txpp_map_hca_bar(struct rte_eth_dev *dev)
 		rte_mem_unmap(base, MLX5_ST_SZ_BYTES(initial_seg));
 	return 0;
 }
-
-- 
2.51.0