[PATCH v4 3/9] net/hns3: adjust return value of xstats-get ops

[Chengwen Feng <fengchengwen@huawei.com>]

Many user (e.g. telemetry) invokes rte_eth_xstats_get(port_id, NULL, 0)
to retrieve the required number of elements, but currently hns3 PMD
returns zero when xstats is NULL.

In the previous patch, the framework defines that the required number
of entries should be returned when xstats is NULL and n is zero. And
xstats is NULL if and only if n is zero.

Based on the preceding constraints, this patch removes the logic of
"return zero when xstats is NULL".

Fixes: 8839c5e202f3 ("net/hns3: support device stats")
Cc: stable@dpdk.org

Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
---
 drivers/net/hns3/hns3_stats.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/net/hns3/hns3_stats.c b/drivers/net/hns3/hns3_stats.c
index 806720faff..ac1f0d9126 100644
--- a/drivers/net/hns3/hns3_stats.c
+++ b/drivers/net/hns3/hns3_stats.c
@@ -1020,9 +1020,13 @@ hns3_imissed_stats_get(struct rte_eth_dev *dev, struct rte_eth_xstat *xstats,
  * @praram xstats
  *   A pointer to a table of structure of type *rte_eth_xstat*
  *   to be filled with device statistics ids and values.
- *   This parameter can be set to NULL if n is 0.
+ *   This parameter can be set to NULL if and only if n is 0.
  * @param n
  *   The size of the xstats array (number of elements).
+ *   If lower than the required number of elements, the function returns the
+ *   required number of elements.
+ *   If equal to zero, the xstats parameter must be NULL, the function returns
+ *   the required number of elements.
  * @return
  *   0 on fail, count(The size of the statistics elements) on success.
  */
@@ -1041,9 +1045,6 @@ hns3_dev_xstats_get(struct rte_eth_dev *dev, struct rte_eth_xstat *xstats,
 	int count;
 	int ret;
 
-	if (xstats == NULL)
-		return 0;
-
 	count = hns3_xstats_calc_num(dev);
 	if ((int)n < count)
 		return count;
-- 
2.33.0