Re: [PATCH v5 4/4] docs: Add ABI documentation

[Thomas Monjalon <thomas.monjalon-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>]

Thank you Neil for writing this document.
This is a really important change in DPDK.
It would be very good to have comments or acknowledgement from several
developpers. This policy would be enforced by having several Acked-by lines.


2015-01-16 10:33, Neil Horman:
> Adding a document describing rudimentary ABI policy and adding notice space for
> any deprecation announcements
> 
> Signed-off-by: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>
> CC: Thomas Monjalon <thomas.monjalon-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>
> CC: "Richardson, Bruce" <bruce.richardson-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> 
> ---
> Change notes:
> 
> v5) Updated documentation to add notes from Thomas M.
> ---
>  doc/abi.txt | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
>  create mode 100644 doc/abi.txt
> 
> diff --git a/doc/abi.txt b/doc/abi.txt
> new file mode 100644
> index 0000000..14be464
> --- /dev/null
> +++ b/doc/abi.txt
> @@ -0,0 +1,36 @@
> +ABI policy:
> +	ABI versions are set at the time of major release labeling, and ABI may
> +change multiple times between the last labeling and the HEAD label of the git
> +tree without warning
> +
> +	ABI versions, once released are available until such time as their
> +deprecation has been noted here for at least one major release cycle, after it
> +has been tagged.  E.g. the ABI for DPDK 1.8 is shipped, and then the decision to
> +remove it is made during the development of DPDK 1.9.  The decision will be
> +recorded here, shipped with the DPDK 1.9 release, and actually removed when DPDK
> +1.10 ships.
> +
> +	ABI versions may be deprecated in whole, or in part as needed by a given
> +update.
> +
> +	Some ABI changes may be too significant to reasonably maintain multiple
> +versions of.  In those events ABI's may be updated without backward
> +compatibility provided.  The requirements for doing so are:
> +	1) At least 3 acknoweldgements of the need on the dpdk.org
> +	2) A full deprecation cycle must be made to offer downstream consumers
> +sufficient warning of the change.  E.g. if dpdk 2.0 is under development when
> +the change is proposed, a deprecation notice must be added to this file, and
> +released with dpdk 2.0.  Then the change may be incorporated for dpdk 2.1
> +	3) The LIBABIVER variable in the makefilei(s) where the ABI changes are
> +incorporated must be incremented in parallel with the ABI changes themselves
> +
> +	Note that the above process for ABI deprecation should not be undertaken
> +lightly.  ABI stability is extreemely important for downstream consumers of the
> +DPDK, especially when distributed in shared object form.  Every effort should be
> +made to preserve ABI whenever possible.  For instance, reorganizing public
> +structure field for astetic or readability purposes should be avoided as it will
> +cause ABI breakage.  Only significant (e.g. performance) reasons should be seen
> +as cause to alter ABI.