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

[Thomas Monjalon <thomas.monjalon@6wind.com>]

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.