Re: [dpdk-dev] [PATCH v5 2/2] ethdev: fix docs of drivers callbacks getting xstats by IDs

[Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>]

On 9/28/21 7:50 PM, Ferruh Yigit wrote:
> On 9/28/2021 1:05 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 | 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.