Trying to query the link status through new kernel ioctl API
ETHTOOL_GLINKSETTINGS was always failing due to kernel bug.
The bug was fixed on version 4.9
this patch uses the legacy ioctl API for lower kernels.

Fixes: 188408719888 ("net/mlx5: fix support for newer link speeds")
CC: stable@dpdk.org

Signed-off-by: Shahaf Shuler <redacted>
---
while the ETHTOOL_GLINKSETTINGS API was introduced on kernel v4.6 [1]                   
the bug was fixed only on kernel v4.9 [2]                                               
                                                                                        
[1] https://github.com/torvalds/linux/commit/3f1ac7a700d039c61d8d8b99f28d605d489a60cf   
[2] https://github.com/torvalds/linux/commit/8006f6bf5e39f11c697f48df20382b81d2f2f8b8   
---
 drivers/net/mlx5/mlx5_ethdev.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_ethdev.c b/drivers/net/mlx5/mlx5_ethdev.c
index 8efdff7..e77238f 100644
--- a/drivers/net/mlx5/mlx5_ethdev.c
+++ b/drivers/net/mlx5/mlx5_ethdev.c

@@ -46,6 +46,7 @@
 #include <netinet/in.h>
 #include <linux/ethtool.h>
 #include <linux/sockios.h>
+#include <linux/version.h>
 #include <fcntl.h>
 
 /* DPDK headers don't like -pedantic. */

@@ -697,7 +698,7 @@ struct priv *
 
 /**
  * Retrieve physical link information (unlocked version using new ioctl from
- * Linux 4.5).
+ * Linux 4.9).
  *
  * @param dev
  *   Pointer to Ethernet device structure.

@@ -707,7 +708,7 @@ struct priv *
 static int
 mlx5_link_update_unlocked_gs(struct rte_eth_dev *dev, int wait_to_complete)
 {
-#ifdef ETHTOOL_GLINKSETTINGS
+#if KERNEL_VERSION(4, 9, 0) <= LINUX_VERSION_CODE
 	struct priv *priv = mlx5_get_priv(dev);
 	struct ethtool_link_settings edata = {
 		.cmd = ETHTOOL_GLINKSETTINGS,

-- 
1.8.3.1