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

-----Original Message-----
From: dev [mailto:dev-bounces-VfR2kkLFssw@public.gmane.org] On Behalf Of Neil Horman
Sent: Tuesday, January 20, 2015 2:24 PM
To: Iremonger, Bernard
Cc: dev-VfR2kkLFssw@public.gmane.org
Subject: Re: [dpdk-dev] [PATCH v5 4/4] docs: Add ABI documentation

On Tue, Jan 20, 2015 at 01:37:35PM +0000, Iremonger, Bernard wrote:

quoted

quoted

-----Original Message-----
From: dev [mailto:dev-bounces-VfR2kkLFssw@public.gmane.org] On Behalf Of Thomas

Monjalon

quoted

quoted

Sent: Tuesday, January 20, 2015 7:15 AM
To: Neil Horman
Cc: dev-VfR2kkLFssw@public.gmane.org
Subject: Re: [dpdk-dev] [PATCH v5 4/4] docs: Add ABI documentation

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.

quoted

quoted

2015-01-16 10:33, Neil Horman:

quoted

Adding a document describing rudimentary ABI policy and adding
notice space for any deprecation announcements

Signed-off-by: Neil Horman <redacted>
CC: Thomas Monjalon <redacted>
CC: "Richardson, Bruce" <redacted>

---
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:

quoted

quoted

quoted

+	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

quoted

+	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.

Hi Thomas,

Should there be a reference to this document in the programmers guide?

Thats a good question. I think, as Thomas notes, it probably should be
referenced in some way.  The programmers guide might be good.  What
might be better would be checking the deprecation notices and adding them
to the release notes for any given release.

Thoughts?
Neil

quoted

Regards,

Bernard.

Sorry to be pedantic but would you also mind sending it as a .rst file instead of .txt if you're going to send as patches to Programmer's Guide anyway? :)
Thanks,
Siobhan