doc: describe process for new ABI versions

Added a section describing new ABI versions, this provides pointers to
the relevant amended rules that apply during the abi breakage window.
Also remove the large note at the head of the ABI policy describing the
ABI stability process that has taken place over the previous year.

Signed-off-by: Ray Kinsella <mdr@ashroe.eu>

diff --git a/doc/guides/contributing/abi_policy.rst b/doc/guides/contributing/abi_policy.rst
index ab9daf5..e17758a 100644 (file)
--- a/doc/guides/contributing/abi_policy.rst
+++ b/doc/guides/contributing/abi_policy.rst
@@ -14,8 +14,8 @@ General Guidelines
 ------------------
 
 #. Major ABI versions are declared no more frequently than yearly. Compatibility
-   with the major ABI version is mandatory in subsequent releases until a new
-   major ABI version is declared.
+   with the major ABI version is mandatory in subsequent releases until a
+   :ref:`new major ABI version <new_abi_version>` is declared.
 #. Major ABI versions are usually but not always declared aligned with a
    :ref:`LTS release <stable_lts_releases>`.
 #. The ABI version is managed at a project level in DPDK, and is reflected in
@@ -35,12 +35,6 @@ General Guidelines
 
 .. note::
 
-   In 2019, the DPDK community stated its intention to move to ABI stable
-   releases, over a number of release cycles. This change begins with
-   maintaining ABI stability through one year of DPDK releases starting from
-   DPDK 19.11. This policy will be reviewed in 2020, with intention of
-   lengthening the stability period. Additional implementation detail can be
-   found in the :ref:`release notes <20_02_abi_changes>`.
    Please note that this policy does not currently apply to the
    :doc:`Windows build <../windows_gsg/intro>`.
 
@@ -288,6 +282,35 @@ added to the Release Notes:
   these changes. Binaries using this library built prior to ABI version 21 will
   require updating and recompilation.
 
+
+.. _new_abi_version:
+
+New ABI versions
+------------------
+
+A new ABI version may be declared aligned with a given release.
+The requirement to preserve compatibility with the previous major ABI version
+is then dropped for the duration of this release cycle.
+This is commonly known as the *ABI breakage window*,
+and some amended rules apply during this cycle:
+
+ * The requirement to preserve compatibility with the previous major ABI
+   version, as described in the section :ref:`abi_changes` does not apply.
+ * Contributors of compatibility preserving code in previous releases,
+   are now required to remove this compatibility code,
+   as described in the section :ref:`abi_changes`.
+ * Symbol versioning references to the old ABI version are updated
+   to reference the new ABI version,
+   as described in the section :ref:`deprecating_entire_abi`.
+ * Contributors of aliases to experimental in previous releases,
+   as described in section :ref:`aliasing_experimental_symbols`,
+   are now required to remove these aliases.
+ * Finally, the *ABI breakage window* is *not* permission to circumvent
+   the other aspects of the procedures to make ABI changes
+   described in :ref:`abi_changes`, that is, 3 ACKs of the requirement
+   to break the ABI and the observance of a deprecation notice
+   are still considered mandatory.
+
 .. _experimental_apis:
 
 Experimental

diff --git a/doc/guides/contributing/abi_versioning.rst b/doc/guides/contributing/abi_versioning.rst
index b1d09c7..7a771db 100644 (file)
--- a/doc/guides/contributing/abi_versioning.rst
+++ b/doc/guides/contributing/abi_versioning.rst
@@ -673,9 +673,9 @@ symbols.
  -BIND_DEFAULT_SYMBOL(rte_acl_create, _v20, 20);
  +BIND_DEFAULT_SYMBOL(rte_acl_create, _v21, 21);
 
-Lastly, any VERSION_SYMBOL macros that point to the old version node should be
-removed, taking care to keep, where need old code in place to support newer
-versions of the symbol.
+Lastly, any VERSION_SYMBOL macros that point to the old version nodes
+should be removed, taking care to preserve any code that is shared
+with the new version node.
 
 
 Running the ABI Validator