[dpdk-dev,v9,4/4] docs: Add ABI documentation

Message ID 1422898822-16422-4-git-send-email-nhorman@tuxdriver.com (mailing list archive)
State Accepted, archived

Commit Message

Neil Horman Feb. 2, 2015, 5:40 p.m. UTC
  Adding a document describing rudimentary ABI policy and adding notice space for
any deprecation announcements

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: Thomas Monjalon <thomas.monjalon@6wind.com>
CC: "Richardson, Bruce" <bruce.richardson@intel.com>

Change notes:

v5) Updated documentation to add notes from Thomas M.

v6) Moved abi.txt to guides/rel_notes/abi.rst

v7) Updated abi.rst to integrate with index file
    Updated abi.rst to conform to rst formatting
    Updated abi.rst to include example deprecation notices.  Its not exactly the
language that Thomas indicated, but I think it makes the idea clear.

v8) Add missing file index.rst which was left out of the prior commit

v9) Fixed typos
 doc/guides/rel_notes/abi.rst   | 40 ++++++++++++++++++++++++++++++++++++++++
 doc/guides/rel_notes/index.rst |  1 +
 2 files changed, 41 insertions(+)
 create mode 100644 doc/guides/rel_notes/abi.rst


Thomas Monjalon Feb. 3, 2015, 3:24 p.m. UTC | #1
> Adding a document describing rudimentary ABI policy and adding notice space for
> any deprecation announcements
> Signed-off-by: Neil Horman <nhorman@tuxdriver.com>

Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>

Thanks Neil for writing the policy.

The version 2.0 will be the first to have a versioned ABI with LIBABIVER := 1.
Starting from there, we'll have to consider this ABI policy when preparing
next versions.


diff --git a/doc/guides/rel_notes/abi.rst b/doc/guides/rel_notes/abi.rst
new file mode 100644
index 0000000..2b16d93
--- /dev/null
+++ b/doc/guides/rel_notes/abi.rst
@@ -0,0 +1,40 @@ 
+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:
+#. At least 3 acknoweldgements of the need on the dpdk.org
+#. 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
+#. 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.
+Examples of Deprecation Notices
+* The Macro #RTE_FOO is deprecated and will be removed with version 2.0, to be replaced with the inline function rte_bar()
+* The function rte_mbuf_grok has been updated to include new parameter in version 2.0.  Backwards compatibility will be maintained for this function until the release of version 2.1
+* The members struct foo have been reorganized in release 2.0.  Existing binary applications will have backwards compatibility in release 2.0, while newly built binaries will need to reference new structure variant struct foo2.  Compatibility will be removed in release 2.2, and all applications will require updating and rebuilding to the new structure at that time, which will be renamed to the origional struct foo.
+* Significant ABI changes are planned for the librte_dostuff library.  The upcoming release 2.0 will not contain these changes, but release 2.1 will, and no backwards compatibility is planned due to the invasive nature of these changes.  Binaries using this library built prior to version 2.1 will require updating and recompilation.
+Deprecation Notices
diff --git a/doc/guides/rel_notes/index.rst b/doc/guides/rel_notes/index.rst
index 2724149..cf712b2 100644
--- a/doc/guides/rel_notes/index.rst
+++ b/doc/guides/rel_notes/index.rst
@@ -48,4 +48,5 @@  Contents
+    abi