On 9/28/2021 5:53 PM, Andrew Rybchenko wrote:

On 9/28/21 7:50 PM, Ferruh Yigit wrote:

quoted

On 9/28/2021 1:05 PM, Andrew Rybchenko wrote:

quoted

From: Ivan Ilchenko <redacted>

Update xstats by IDs callbacks documentation in accordance with
ethdev usage of these callbacks. Document valid combinations of
input arguments to make driver implementation simpler.

Fixes: 79c913a42f0 ("ethdev: retrieve xstats by ID")
Cc: stable@dpdk.org

Signed-off-by: Ivan Ilchenko <redacted>
Signed-off-by: Andrew Rybchenko <redacted>
Reviewed-by: Andy Moreton <redacted>
---
 lib/ethdev/ethdev_driver.h | 42 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 40 insertions(+), 2 deletions(-)

diff --git a/lib/ethdev/ethdev_driver.h b/lib/ethdev/ethdev_driver.h
index 40e474aa7e..c89eefcc42 100644
--- a/lib/ethdev/ethdev_driver.h
+++ b/lib/ethdev/ethdev_driver.h

@@ -187,11 +187,28 @@ typedef int (*eth_xstats_get_t)(struct rte_eth_dev *dev,
 	struct rte_eth_xstat *stats, unsigned int n);
 /**< @internal Get extended stats of an Ethernet device. */
 
+/**
+ * @internal
+ * Get extended stats of an Ethernet device.
+ *
+ * @param dev
+ *   ethdev handle of port.
+ * @param ids
+ *   IDs array to retrieve specific statistics. Must not be NULL.
+ * @param values
+ *   A pointer to a table to be filled with device statistics values.
+ *   Must not be NULL.
+ * @param n
+ *   Element count in @p ids and @p values.
+ *
+ * @return
+ *   - A number of filled in stats.
+ *   - A negative value on error.
+ */
 typedef int (*eth_xstats_get_by_id_t)(struct rte_eth_dev *dev,
 				      const uint64_t *ids,
 				      uint64_t *values,
 				      unsigned int n);
-/**< @internal Get extended stats of an Ethernet device. */
 
 /**
  * @internal

@@ -218,10 +235,31 @@ typedef int (*eth_xstats_get_names_t)(struct rte_eth_dev *dev,
 	struct rte_eth_xstat_name *xstats_names, unsigned int size);
 /**< @internal Get names of extended stats of an Ethernet device. */
 
+/**
+ * @internal
+ * Get names of extended stats of an Ethernet device.
+ * For name count, set @p xstats_names and @p ids to NULL.

Why limiting this behavior to 'xstats_get_names_by_id'?

Internally 'xstats_get_names_by_id' is used to get the count, but I think this
is not intentionally selected, just one of the xstats_*_by_id dev_ops used.

I think it is confusing to have this support for one of the '_by_id' dev_ops but
not for other. Why not require both to support returning 'count'?

Simply because it is dead code. There is no point to require
from driver to have dead code.

Let me step back a little, both ethdev APIs can be used to return xstats count
by providing 'values/names' & 'ids' pointers as NULL and 'size' as 0:
'rte_eth_xstats_get_names_by_id()'
'rte_eth_xstats_get_by_id()'

But internally both APIs use 'xstats_get_names_by_id' dev_ops to get the count,
as said above I believe this selection is done unintentionally.


I am for below two options:

a) Internally use 'xstats_get_names' || 'xstats_get' dev_ops to get the xstats
count, and doesn't support getting xstats count for both '_by_id' dev_ops, this
simplifies driver code. As far as I remember I suggested this before, still I
prefer this one.

b) If we will support getting xstats count from '_by_id' dev_ops, I think both
should support it, to not make it more complex to figure out which one support
what. As sample both 'xstats_get_names' and 'xstats_get' supports getting xstats
count, not just one.