Re: [dpdk-dev] [PATCH 04/11] ethdev: fix docs of drivers callbacks getting xstats by IDs

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 7/22/2021 10:33 AM, Andrew Rybchenko wrote:
> On 7/20/21 7:51 PM, Ferruh Yigit wrote:
>> On 6/4/2021 3:42 PM, Andrew Rybchenko wrote:
>>> From: Ivan Ilchenko <ivan.ilchenko@oktetlabs.ru>
>>>
>>> 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 <ivan.ilchenko@oktetlabs.ru>
>>> Signed-off-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>>> Reviewed-by: Andy Moreton <amoreton@xilinx.com>
>>> ---
>>>   lib/ethdev/ethdev_driver.h | 43 ++++++++++++++++++++++++++++++++++++--
>>>   1 file changed, 41 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/lib/ethdev/ethdev_driver.h b/lib/ethdev/ethdev_driver.h
>>> index 40e474aa7e..fd5b7ca550 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.
>>
>> Should it mention _by_id detail?
> 
> Yes, will fix in v2.
> 
>>> + *
>>> + * @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 +235,32 @@ 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.
>>
>> Should it mention _by_id detail?
> 
> Yes, will fix in v2.
> 
>>> + * For name count, set @p xstats_names and @p ids to NULL.
>>> + *
>>
>> isn't the 'count' part handled in the API? I think in the devops both should not
>> be NULL.
> 
> No, eth_dev_get_xstats_count() uses the callback with NULL, NULL, 0.
> 

Right, I missed it, xstats_get_names_by_id() seems used outside of the ethdev
_by_id() APIs.

>>
>>> + * @param dev
>>> + *   ethdev handle of port.
>>> + * @param xstats_names
>>> + *   An rte_eth_xstat_name array of at least *size* elements to
>>> + *   be filled. Can be NULL together with @p ids to retrieve number of
>>> + *   available statistics.
>>
>> As far as I understand both _by_id APIs and devops behave same, so argument
>> descriptions/behavior should be same.
> 
> In fact no, it is slightly different. For example, devops is never
> called with NULL ids and not NULL names or non-zero size. It allows to
> check less in drivers.
> 

I am not sure if this difference is intentional.

'eth_dev_get_xstats_count()' is ethdev internal function, what do you think
removing 'xstats_get_names_by_id()' call from it. And make both _by_id() dev_ops
doesn't accept NULL ids and NULL values/names, so simplifies PMD implementations.

>>> + * @param ids
>>> + *   IDs array to retrieve specific statistics. Can be NULL together
>>> + *   with @p xstats_names to retrieve number of available statistics.
>>> + * @param size
>>> + *   Size of ids and xstats_names arrays.
>>> + *   Element count in @p ids and @p xstats_names
>>> + *
>>> + * @return
>>> + *   - A number of filled in stats if both xstats_names and ids are not NULL.
>>> + *   - A number of available stats if both xstats_names and ids are NULL.
>>
>> Again as far as I can see these covered by API, not devops, am I missing
>> something.
> 
> See eth_dev_get_xstats_count()
> 
>>
>>> + *   - A negative value on error.
>>> + */
>>>   typedef int (*eth_xstats_get_names_by_id_t)(struct rte_eth_dev *dev,
>>>       struct rte_eth_xstat_name *xstats_names, const uint64_t *ids,
>>>       unsigned int size);
>>> -/**< @internal Get names of extended stats of an Ethernet device. */
>>>     typedef int (*eth_queue_stats_mapping_set_t)(struct rte_eth_dev *dev,
>>>                            uint16_t queue_id,
>>>
>