Re: [PATCH v2 0/5] example/ethtool: add bus info and fw version get

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

On 12/22/2016 3:31 PM, Thomas Monjalon wrote:
> 2016-12-22 15:05, Ferruh Yigit:
>> On 12/22/2016 2:47 PM, Thomas Monjalon wrote:
>>> 2016-12-22 14:36, Ferruh Yigit:
>>>> On 12/22/2016 11:07 AM, Thomas Monjalon wrote:
>>>>> I think it is OK to add a new dev_ops and a new API function for firmware
>>>>> query. Generally speaking, it is a good thing to avoid putting all
>>>>> informations in the same structure (e.g. rte_eth_dev_info). 
>>>>
>>>> OK.
>>>>
>>>>> However, there
>>>>> is a balance to find. Could we plan to add more info to this new query?
>>>>> Instead of
>>>>> 	rte_eth_dev_fwver_get(uint8_t port_id, char *fw_version, int fw_length)
>>> [...]
>>>>> could it fill a struct?
>>>>> 	rte_eth_dev_fw_info_get(uint8_t port_id, struct rte_eth_dev_fw_info *fw_info)
>>>>
>>>> I believe this is better. But the problem we are having with this usage
>>>> is: ABI breakage.
>>>>
>>>> Since this struct will be a public structure, in the future if we want
>>>> to add a new field to the struct, it will break the ABI, and just this
>>>> change will cause a new version for whole ethdev library!
>>>>
>>>> When all required fields received via arguments, one by one, instead of
>>>> struct, at least ABI versioning can be done on the API when new field
>>>> added, and can be possible to escape from ABI breakage. But this will be
>>>> ugly when number of arguments increased.
>>>>
>>>> Or any other opinion on how to define API to reduce ABI breakage?
>>>
>>> You're right.
>>> But I don't think we should have a function per data. Just because it would
>>> be ugly :)
>>
>> I am no suggesting function per data, instead something like:
>>
>> rte_eth_dev_fw_info_get(uint8_t port_id, uint32_t maj, uint32_t min);
>>
>> And in the future if we need etrack_id too, we can have both in
>> versioned manner:
>>
>> rte_eth_dev_fw_info_get(uint8_t port_id, uint32_t maj, uint32_t min);
>>
>> rte_eth_dev_fw_info_get(uint8_t port_id, uint32_t maj, uint32_t min,
>> 	uint32_t etrack_id);
> 
> Oh I see. So it can be versioned with compat macros.
> 
>> So my concern was if the number of the arguments becomes too many by time.
> 
> It looks to be a good proposal. We should not have a dozen of arguments.
> 

So, I suggest trying this approach in this API.


Overall, change request for the patch becomes:
1- Change API, is following arguments good enough to start with?:
- FW_major_number
- FW_minor_number
- FW_patch_number
- Etrack_id

If so, API becomes:
rte_eth_dev_fw_version_get(uint8_t port_id, uint32_t *fw_major,
	uint32_t *fw_minor, uint32_t *fw_patch, uint32_t *etrack_id);

! Note, I have renamed API to rte_eth_dev_fw_version_get() from
rte_eth_dev_fw_info_get() mentioned above, to narrow the scope of API.

and dev_ops name keeps same: fw_version_get

2- Add new feature in feature table (doc/guides/nics/features/), first
patch can add to the default one, and each driver patch implements this
feature should update its feature table.
Feature name can be "FW version"

3- Remove deprecation notice in the first patch.


Thanks,
ferruh