Re: [dpdk-dev] [PATCH v7 02/14] ethdev: add support for hairpin queue

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 11/5/19 4:02 PM, Thomas Monjalon wrote:
> 05/11/2019 13:53, Andrew Rybchenko:
>> On 11/5/19 3:51 PM, Thomas Monjalon wrote:
>>> 05/11/2019 13:27, Andrew Rybchenko:
>>>> On 11/5/19 3:23 PM, Ferruh Yigit wrote:
>>>>> On 11/5/2019 12:12 PM, Andrew Rybchenko wrote:
>>>>>> On 11/5/19 3:05 PM, Ferruh Yigit wrote:
>>>>>>> On 11/5/2019 11:49 AM, Andrew Rybchenko wrote:
>>>>>>>> On 11/5/19 2:36 PM, Ori Kam wrote:
>>>  >>>>>> From: Ferruh Yigit <ferruh.yigit@intel.com>
>>>>>>>>>>>  /**
>>>>>>>>>>> + * @internal
>>>>>>>>>>> + * Check if the selected Rx queue is hairpin queue.
>>>>>>>>>>> + *
>>>>>>>>>>> + * @param dev
>>>>>>>>>>> + *  Pointer to the selected device.
>>>>>>>>>>> + * @param queue_id
>>>>>>>>>>> + *  The selected queue.
>>>>>>>>>>> + *
>>>>>>>>>>> + * @return
>>>>>>>>>>> + *   - (1) if the queue is hairpin queue, 0 otherwise.
>>>>>>>>>>> + */
>>>>>>>>>>> +int
>>>>>>>>>>> +rte_eth_dev_is_rx_hairpin_queue(struct rte_eth_dev *dev, uint16_t
>>>>>>>>>> queue_id);
>>>>>>>>>>> +
>>>>>>>>>>> +/**
>>>>>>>>>>> + * @internal
>>>>>>>>>>> + * Check if the selected Tx queue is hairpin queue.
>>>>>>>>>>> + *
>>>>>>>>>>> + * @param dev
>>>>>>>>>>> + *  Pointer to the selected device.
>>>>>>>>>>> + * @param queue_id
>>>>>>>>>>> + *  The selected queue.
>>>>>>>>>>> + *
>>>>>>>>>>> + * @return
>>>>>>>>>>> + *   - (1) if the queue is hairpin queue, 0 otherwise.
>>>>>>>>>>> + */
>>>>>>>>>>> +int
>>>>>>>>>>> +rte_eth_dev_is_tx_hairpin_queue(struct rte_eth_dev *dev, uint16_t
>>>>>>>>>> queue_id);
>>> [...]
>>>>>>>>>> These are causing build error, thanks Jerin for catching, because they are
>>>>>>>>>> internal and called by a public static inline API, so whoever calls
>>>>>>>>>> 'rte_eth_rx/tx_burst()' APIs in the shared build, can't find
>>>>>>>>>> 'rte_eth_dev_is_rx/tx_hairpin_queue()' functions [1],
>>>>>>>>>>
>>>>>>>>>> as far as I can see there are two options:
>>>>>>>>>> 1) Remove these checks
>>>>>>>>>> 2) Make 'rte_eth_dev_is_rx/tx_hairpin_queue()' public API instead of internal
>>>>>>>>>>
>>>>>>>>>> If there is a value to make 'rte_eth_dev_is_rx/tx_hairpin_queue()' public API
>>>>>>>>>> we
>>>>>>>>>> should go with (2) else (1).
>>>>>>>>>>
>>>>>>>>> I think we can skip the tests,
>>>>>>>>> But it was Andrew request so we must get is response.
>>>>>>>>> It was also his empathies that they should be internal.
>>>>>>>> It is important for me to keep rte_eth_dev_state internal and
>>>>>>>> few patches ago rte_eth_dev_is_rx_hairpin_queue() was inline.
>>>>>>> Are you saying you don't want to option to make
>>>>>>> 'rte_eth_dev_is_rx_hairpin_queue()' static inline because it will force the
>>>>>>> 'RTE_ETH_QUEUE_STATE_xxx' being public?
>>>>>> Yes.
>>>>> +1
>>>>>
>>>>>>>> I'm OK to make the function experimental or keep it internal
>>>>>>>> (no API/ABI stability requirements) but externally visible (in .map).
>>>>>>> I think we can't do this, add a function deceleration to the public header file
>>>>>>> and add it to the .map file but keep it internal. Instead we can make it a
>>>>>>> proper API and it should be experimental at least first release.
>>>>>> We have discussed similar thing with Olivier recently [1].
>>>>>>
>>>>>> [1] http://inbox.dpdk.org/dev/20191030142938.bpi4txlrebqfq7uw@platinum/
>>>>> Yes we can say they are internal but there won't be anything preventing
>>>>> applications to use them.
>>>> That's true, but making it internal says - don't use it.
>>>> Anyway, I have no strong opinion on experimental vs internal.
>>>>
>>>>>>> The question above was do we need this API, or instead should remove the check
>>>>>>> from rx/tx_burst APIs?
>>>>>> I think these checks are useful to ensure that these functions
>>>>>> are not used for hairpin queues. At least to catch it with debug
>>>>>> enabled.
>>>>> OK, if so what not make them proper API? Any concern on it?
>>> Why we should not use this API in applications?
>> I think the valid question is why application needs the API.
>> Basically I don't mind, just want to be sure that only required
>> API is exposed.
> Because hairpin queues are not standard queues,
> we may need to distinguish them.
> I see it as a good helper for applications.
> Am I missing something obvious?

I think no. I would prefer explicit reason, but since
these function are simple, I'm OK to go with
"may need to distinguish them"