doc: add prog guide section documenting pmdinfo script

Information on pmdinfogen may be useful to 3rd party driver developers.
Include documentation on what it does

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Panu Matilainen <pmatilai@redhat.com>
Acked-by: John McNamara <john.mcnamara@intel.com>
Acked-by: Remy Horton <remy.horton@intel.com>

diff --git a/doc/guides/prog_guide/dev_kit_build_system.rst b/doc/guides/prog_guide/dev_kit_build_system.rst
index 3e89eae..1dc1388 100644 (file)
--- a/doc/guides/prog_guide/dev_kit_build_system.rst
+++ b/doc/guides/prog_guide/dev_kit_build_system.rst
@@ -70,7 +70,7 @@ Each build directory contains include files, libraries, and applications:
     ...
     ~/DEV/DPDK$ ls i686-native-linuxapp-gcc
 
-    app build hostapp include kmod lib Makefile
+    app build buildtools include kmod lib Makefile
 
 
     ~/DEV/DPDK$ ls i686-native-linuxapp-gcc/app/
@@ -264,7 +264,7 @@ These Makefiles generate a binary application.
 
 *   rte.extapp.mk: External application
 
-*   rte.hostapp.mk: Host application in the development kit framework
+*   rte.hostapp.mk: prerequisite tool to build dpdk
 
 Library
 ^^^^^^^
@@ -304,6 +304,45 @@ Misc
 
 *   rte.subdir.mk: Build several directories in the development kit framework.
 
+.. _Internally_Generated_Build_Tools:
+
+Internally Generated Build Tools
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``app/pmdinfogen``
+
+
+``pmdinfogen`` scans an object (.o) file for various well known symbol names.  These
+well known symbol names are defined by various macros and used to export
+important information about hardware support and usage for pmd files.  For
+instance the macro:
+
+.. code-block:: c
+
+    PMD_REGISTER_DRIVER(drv, name)
+
+
+Creates the following symbol:
+
+.. code-block:: c
+
+   static char this_pmd_name0[] __attribute__((used)) = "<name>";
+
+
+Which pmdinfogen scans for.  Using this information other relevant bits of data
+can be exported from the object file and used to produce a hardware support
+description, that pmdinfogen then encodes into a json formatted string in the
+following format:
+
+.. code-block:: C
+
+   static char <name_pmd_string>="PMD_INFO_STRING=\"{'name' : '<name>', ...}\"";
+
+
+These strings can then be searched for by external tools to determine the
+hardware support of a given library or application.
+
+
 .. _Useful_Variables_Provided_by_the_Build_System:
 
 Useful Variables Provided by the Build System