Re: [dpdk-dev] [PATCH] meter: provide experimental alias of API for old apps

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

On 5/13/2020 5:30 PM, Thomas Monjalon wrote:
> I think the title should be about ABI, not API.
> 
> 13/05/2020 14:11, Ferruh Yigit:
>> Duplicate the existing and versioned symbol as experimental.
> 
> Would be good to explain the case of the meter lib you are addressing.
> If I understand well, you consider we "broke" the experimental ABI
> during 20.02 when moving symbols from EXPERIMENTAL to DPDK_20.0.1
> (and to DPDK_21 during 20.05).
> That's why you want to add back the EXPERIMENTAL symbol as an alias
> of the symbol in the next ABI (21).

Yes, this is the case, I can try again to clarify.

Btw, I wasn't following that bit, how we are mitigating the affect of the
DPDK_20.0.1 -> DPDK_21 change to applications?


> 
> 
>> This is to prevent DPDK maturing experimental API breaking old
>> applications using that experimental API.
>> The relevant process update is captured in:
>> https://patches.dpdk.org/patch/65863/
>>
>> Created VERSION_SYMBOL_EXPERIMENTAL helper macro.
>>
>> Updated the 'check-experimental-syms.sh' buildtool, which was
>> complaining that the symbol is in EXPERIMENTAL tag in .map file but it
>> is not in the .experimental section (__rte_experimental tag is missing).
>> Updated tool in a way it won't complain if the symbol in the
>> EXPERIMENTAL tag duplicated in some other block in .map file (versioned)
>>
>> Enabled function versioning for meson build for the library.
>>
>> Fixes: 30512af820fe ("meter: remove experimental flag from RFC4115 trTCM API")
> 
> Even if it's never backported, it would be more correct to add Cc: stable
> to indicate it is fixing previous release (20.02 here).

As you said original patch is after LTS, but yes I can add the tag.
(Although not having stable tag implies the fix is not in this release, it also
may mean backport is not requested as been in this case.)

> 
> 
>> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
> [...]
>> --- a/lib/librte_meter/rte_meter_version.map
>> +++ b/lib/librte_meter/rte_meter_version.map
>> @@ -20,4 +20,12 @@ DPDK_21 {
>>  	rte_meter_trtcm_rfc4115_color_blind_check;
>>  	rte_meter_trtcm_rfc4115_config;
>>  	rte_meter_trtcm_rfc4115_profile_config;
>> +
>>  } DPDK_20.0;
>> +
>> +EXPERIMENTAL {
>> +       global:
>> +
>> +	rte_meter_trtcm_rfc4115_config;
>> +	rte_meter_trtcm_rfc4115_profile_config;
>> +};
>>
> 
> 
> 
> 
>