doc: add note on hardware support deprecation

[dpdk.git] / doc / guides / contributing / versioning.rst

diff --git a/doc/guides/contributing/versioning.rst b/doc/guides/contributing/versioning.rst
index fbc44a7..8d0fdb7 100644 (file)
--- a/doc/guides/contributing/versioning.rst
+++ b/doc/guides/contributing/versioning.rst
@@ -18,6 +18,8 @@ General Guidelines
 #. The modification of symbols can generally be managed with versioning
 #. The removal of symbols generally is an ABI break and requires bumping of the
    LIBABIVER macro
+#. Updates to the minimum hardware requirements, which drop support for hardware which
+   was previously supported, should be treated as an ABI change.
 
 What is an ABI
 --------------
@@ -77,6 +79,13 @@ for significant reasons, such as performance enhancements. ABI breakage due to
 changes such as reorganizing public structure fields for aesthetic or
 readability purposes should be avoided.
 
+.. note::
+
+   Updates to the minimum hardware requirements, which drop support for hardware
+   which was previously supported, should be treated as an ABI change, and
+   follow the relevant deprecation policy procedures as above: 3 acks and
+   announcement at least one release in advance.
+
 Examples of Deprecation Notices
 -------------------------------
 
@@ -133,6 +142,31 @@ The macros exported are:
   fully qualified function ``p``, so that if a symbol becomes versioned, it
   can still be mapped back to the public symbol name.
 
+Setting a Major ABI version
+---------------------------
+
+Downstreams might want to provide different DPDK releases at the same time to
+support multiple consumers of DPDK linked against older and newer sonames.
+
+Also due to the interdependencies that DPDK libraries can have applications
+might end up with an executable space in which multiple versions of a library
+are mapped by ld.so.
+
+Think of LibA that got an ABI bump and LibB that did not get an ABI bump but is
+depending on LibA.
+
+.. note::
+
+    Application
+    \-> LibA.old
+    \-> LibB.new -> LibA.new
+
+That is a conflict which can be avoided by setting ``CONFIG_RTE_MAJOR_ABI``.
+If set, the value of ``CONFIG_RTE_MAJOR_ABI`` overwrites all - otherwise per
+library - versions defined in the libraries ``LIBABIVER``.
+An example might be ``CONFIG_RTE_MAJOR_ABI=16.11`` which will make all libraries
+``librte<?>.so.16.11`` instead of ``librte<?>.so.<LIBABIVER>``.
+
 Examples of ABI Macro use
 -------------------------