[dpdk-dev] [PATCH] doc: announce ABI change for mbuf structure

[Bruce Richardson]

On Tue, Jul 19, 2016 at 04:01:15PM +0200, Olivier Matz wrote:
> For 16.11, the mbuf structure will be modified implying ABI breakage.
> Some discussions already took place here:
> http://www.dpdk.org/dev/patchwork/patch/12878/
> 
> Signed-off-by: Olivier Matz <olivier.matz at 6wind.com>
> ---
>  doc/guides/rel_notes/deprecation.rst | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
> index f502f86..2245bc2 100644
> --- a/doc/guides/rel_notes/deprecation.rst
> +++ b/doc/guides/rel_notes/deprecation.rst
> @@ -41,3 +41,9 @@ Deprecation Notices
>  * The mempool functions for single/multi producer/consumer are deprecated and
>    will be removed in 16.11.
>    It is replaced by rte_mempool_generic_get/put functions.
> +
> +* ABI changes are planned for 16.11 in the ``rte_mbuf`` structure: some
> +  fields will be reordered to facilitate the writing of ``data_off``,
> +  ``refcnt``, and ``nb_segs`` in one operation. Indeed, some platforms
> +  have an overhead if the store address is not naturally aligned. The
> +  useless ``port`` field will also be removed at the same occasion.
> -- 

Have we fully bottomed out on the mbuf changes. I'm not sure that once patches
start getting considered for merge, new opinions may come forward. For instance,
is the "port" field really "useless"?

Would it not be better to put in a less specific deprecation notice? What happens
if this notice goes in and the final changes are different from those called out
here?

/Bruce