[dpdk-stable] [PATCH] common/mlx5: fix compilation for zero-length array

[Matan Azrad <matan@nvidia.com>]

The structure of the striding RQ(MPRQ) buffer includes an array size
defined by the RTE_PKTMBUF_HEADROOM macro added in [1].

When RTE_PKTMBUF_HEADROOM is set to 0 in the compilation config file the
the compilation with debug type failed:

"In file included from ../drivers/common/mlx5/mlx5_common.h:25,
                 from ../drivers/common/mlx5/linux/mlx5_nl.h:12,
                 from ../drivers/common/mlx5/linux/mlx5_nl.c:22:
../drivers/common/mlx5/mlx5_common_mr.h:96:10: error: ISO C forbids
                             zero-size array 'pad' [-Werror=pedantic]"

Actually, the array for the first stride headroom is not needed:

Each stride in the striding RQ buffer includes the headroom of the next
stride, so the headroom of the first stride should be allocated before
the starting point of the buffer posted to the HW(HW buffer).

The striding RQ buffer is used as an attached buffer to mbuf and have
shared information per stride.

The LRO support moved all the strides shared information to the top of
the buffer before the first stride headroom but didn't remove the old
memory of this headroom from the buffer.

Remove the old headroom memory from the striding RQ buffer.

Fixes: 3a22f3877c9d ("net/mlx5: replace external mbuf shared memory")
Cc: stable@dpdk.org

[1] commit 7d6bf6b866b8 ("net/mlx5: add Multi-Packet Rx support")

Signed-off-by: Matan Azrad <matan@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
---
 drivers/common/mlx5/mlx5_common_mr.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/common/mlx5/mlx5_common_mr.h b/drivers/common/mlx5/mlx5_common_mr.h
index e74f81641c..748dfc68b0 100644
--- a/drivers/common/mlx5/mlx5_common_mr.h
+++ b/drivers/common/mlx5/mlx5_common_mr.h
@@ -93,7 +93,6 @@ struct mlx5_mr_share_cache {
 struct mlx5_mprq_buf {
 	struct rte_mempool *mp;
 	uint16_t refcnt; /* Atomically accessed refcnt. */
-	uint8_t pad[RTE_PKTMBUF_HEADROOM]; /* Headroom for the first packet. */
 	struct rte_mbuf_ext_shared_info shinfos[];
 	/*
 	 * Shared information per stride.
-- 
2.25.1