Re: [dpdk-dev] [PATCH] doc: deprecate using MAX values as array size

[David Marchand <david.marchand@redhat.com>]

On Thu, Jan 30, 2020 at 3:20 PM Ferruh Yigit <ferruh.yigit@intel.com> wrote:
> Adding the deprecation notice as reminder for next ABI breakage release
> (20.11).
> This one time breakage is required to be able to extend enum/define
> without breaking ABI.
>
> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
> ---
>  doc/guides/rel_notes/deprecation.rst | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
> index dfcca87ab..99d81564a 100644
> --- a/doc/guides/rel_notes/deprecation.rst
> +++ b/doc/guides/rel_notes/deprecation.rst
> @@ -38,6 +38,20 @@ Deprecation Notices
>    remove it from the externally visible ABI and allow it to be updated in the
>    future.
>
> +* lib: will fix extending some enum/define breaking the ABI. There are multiple
> +  samples in DPDK that enum/define terminated with a ``.*MAX.*`` value which is
> +  used by iterators, and arrays holding these values are sized with this
> +  ``.*MAX.*`` value. So extending this enum/define increases the ``.*MAX.*``
> +  value which increases the size of the array and depending on how/where the
> +  array is used this may break the ABI.
> +  ``RTE_ETH_FLOW_MAX`` is one sample of the mentioned case, adding a new flow
> +  type will break the ABI because of ``flex_mask[RTE_ETH_FLOW_MAX]`` array
> +  usage in following public struct hierarchy:
> +  ``rte_eth_fdir_flex_conf -> rte_fdir_conf -> rte_eth_conf (in the middle)``.
> +  Need to identify this kind of usages and fix in 20.11, otherwise this blocks
> +  us extending existing enum/define.
> +  One solution can be using a fixed size array instead of ``.*MAX.*`` value.
> +
>  * dpaa2: removal of ``rte_dpaa2_memsegs`` structure which has been replaced
>    by a pa-va search library. This structure was earlier being used for holding
>    memory segments used by dpaa2 driver for faster pa->va translation. This
> --
> 2.24.1
>

Acked-by: David Marchand <david.marchand@redhat.com>


--
David Marchand