net/mlx4_en: Use union for BlueFlame WQE

When BlueFlame is turned on, control segment of the TX WQE is changed,
and the second line of it is used for QPN.
Changed code to use a union in the mlx4_wqe_ctrl_seg instead of casting.
This makes the code clearer and solves the static checker warning:

drivers/net/ethernet/mellanox/mlx4/en_tx.c:839 mlx4_en_xmit()
	warn: potential memory corrupting cast 4 vs 2 bytes

CC: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 10 insertions, 4 deletions

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index 56e8fbc128f8..69c2fcef9d4c 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -876,7 +876,8 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
         skb_tx_timestamp(skb);
 
         if (ring->bf_enabled && desc_size <= MAX_BF && !bounce && !vlan_tx_tag_present(skb)) {
-                *(__be32 *) (&tx_desc->ctrl.vlan_tag) |= cpu_to_be32(ring->doorbell_qpn);
+                tx_desc->ctrl.bf_qpn |= cpu_to_be32(ring->doorbell_qpn);
+
                 op_own |= htonl((bf_index & 0xffff) << 8);
                 /* Ensure new descirptor hits memory
                 * before setting ownership of this descriptor to HW */
diff --git a/include/linux/mlx4/qp.h b/include/linux/mlx4/qp.h
index 59f8ba84568b..b66e7610d4ee 100644
--- a/include/linux/mlx4/qp.h
+++ b/include/linux/mlx4/qp.h
@@ -270,9 +270,14 @@ enum {
 
 struct mlx4_wqe_ctrl_seg {
         __be32                  owner_opcode;
-        __be16                  vlan_tag;
-        u8                      ins_vlan;
-        u8                      fence_size;
+        union {
+                struct {
+                        __be16                  vlan_tag;
+                        u8                      ins_vlan;
+                        u8                      fence_size;
+                };
+                __be32                  bf_qpn;
+        };
         /*
          * High 24 bits are SRC remote buffer; low 8 bits are flags:
          * [7]   SO (strong ordering)