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doc: describe how to add new components

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Add to the contributors guide details on how to add libraries and drivers
and integrate them with the DPDK build system(s).

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Reviewed-by: Harry van Haaren <harry.van.haaren@intel.com>
Acked-by: Keith Wiles <keith.wiles@intel.com>
Acked-by: Luca Boccassi <luca.boccassi@gmail.com>
This commit is contained in:
Bruce Richardson 2017-08-31 17:10:16 +01:00
parent 7b67398e60
commit 44a6dface1
1 changed files with 223 additions and 0 deletions
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doc/guides/contributing/coding_style.rst
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@ -702,3 +702,226 @@ All Python code should work with Python 2.7+ and 3.2+ and be compliant with
`PEP8 (Style Guide for Python Code) <https://www.python.org/dev/peps/pep-0008/>`_.
The ``pep8`` tool can be used for testing compliance with the guidelines.
Integrating with the Build System
---------------------------------
DPDK supports being built in two different ways:
* using ``make`` - or more specifically "GNU make", i.e. ``gmake`` on FreeBSD
* using the tools ``meson`` and ``ninja``
Any new library or driver to be integrated into DPDK should support being
built with both systems. While building using ``make`` is a legacy approach, and
most build-system enhancements are being done using ``meson`` and ``ninja``
there are no plans at this time to deprecate the legacy ``make`` build system.
Therefore all new component additions should include both a ``Makefile`` and a
``meson.build`` file, and should be added to the component lists in both the
``Makefile`` and ``meson.build`` files in the relevant top-level directory:
either ``lib`` directory or a ``driver`` subdirectory.
Makefile Contents
~~~~~~~~~~~~~~~~~
The ``Makefile`` for the component should be of the following format, where
``<name>`` corresponds to the name of the library in question, e.g. hash,
lpm, etc. For drivers, the same format of Makefile is used.
.. code-block:: none
# pull in basic DPDK definitions, including whether library is to be
# built or not
include $(RTE_SDK)/mk/rte.vars.mk
# library name
LIB = librte_<name>.a
# any library cflags needed. Generally add "-O3 $(WERROR_FLAGS)"
CFLAGS += -O3
CFLAGS += $(WERROR_FLAGS)
# the symbol version information for the library, and .so version
EXPORT_MAP := rte_<name>_version.map
LIBABIVER := 1
# all source filenames are stored in SRCS-y
SRCS-$(CONFIG_RTE_LIBRTE_<NAME>) += rte_<name>.c
# install includes
SYMLINK-$(CONFIG_RTE_LIBRTE_<NAME>)-include += rte_<name>.h
# pull in rules to build the library
include $(RTE_SDK)/mk/rte.lib.mk
Meson Build File Contents - Libraries
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The ``meson.build`` file for a new DPDK library should be of the following basic
format.
.. code-block:: python
sources = files('file1.c', ...)
headers = files('file1.c', ...)
The will build based on a number of conventions and assumptions within the DPDK
itself, for example, that the library name is the same as the directory name in
which the files are stored.
For a library ``meson.build`` file, there are number of variables which can be
set, some mandatory, others optional. The mandatory fields are:
sources
**Default Value = []**.
This variable should list out the files to be compiled up to create the
library. Files must be specified using the meson ``files()`` function.
The optional fields are:
allow_experimental_apis
**Default Value = false**
Used to allow the library to make use of APIs marked as experimental.
Set to ``true`` if the C files in the library call any functions
marked as experimental in any included header files.
build
**Default Value = true**
Used to optionally compile a library, based on its dependencies or
environment. A simple example of use would be:
.. code-block:: python
if host_machine.system() != 'linux'
build = false
endif
cflags
**Default Value = []**.
Used to specify any additional cflags that need to be passed to compile
the sources in the library.
deps
**Default Value = ['eal']**.
Used to list the internal library dependencies of the library. It should
be assigned to using ``+=`` rather than overwriting using ``=``. The
dependencies should be specified as strings, each one giving the name of
a DPDK library, without the ``librte_`` prefix. Dependencies are handled
recursively, so specifying e.g. ``mempool``, will automatically also
make the library depend upon the mempool library's dependencies too -
``ring`` and ``eal``. For libraries that only depend upon EAL, this
variable may be omitted from the ``meson.build`` file. For example:
.. code-block:: python
deps += ['ethdev']
ext_deps
**Default Value = []**.
Used to specify external dependencies of this library. They should be
returned as dependency objects, as returned from the meson
``dependency()`` or ``find_library()`` functions. Before returning
these, they should be checked to ensure the dependencies have been
found, and, if not, the ``build`` variable should be set to ``false``.
For example:
.. code-block:: python
my_dep = dependency('libX', required: 'false')
if my_dep.found()
ext_deps += my_dep
else
build = false
endif
headers
**Default Value = []**.
Used to return the list of header files for the library that should be
installed to $PREFIX/include when ``ninja install`` is run. As with
source files, these should be specified using the meson ``files()``
function.
name
**Default Value = library name derived from the directory name**.
If a library's .so or .a file differs from that given in the directory
name, the name should be specified using this variable. In practice,
since the convention is that for a library called ``librte_xyz.so``, the
sources are stored in a directory ``lib/librte_xyz``, this value should
never be needed for new libraries.
.. note::
The name value also provides the name used to find the function version
map file, as part of the build process, so if the directory name and
library names differ, the ``version.map`` file should be named
consistently with the library, not the directory
objs
**Default Value = []**.
This variable can be used to pass to the library build some pre-built
objects that were compiled up as part of another target given in the
included library ``meson.build`` file.
version
**Default Value = 1**.
Specifies the ABI version of the library, and is used as the major
version number of the resulting ``.so`` library.
Meson Build File Contents - Drivers
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For drivers, the values are largely the same as for libraries. The variables
supported are:
allow_experimental_apis
As above.
build
As above.
cflags
As above.
deps
As above.
ext_deps
As above.
includes
**Default Value = <driver directory>** Some drivers include a base
directory for additional source files and headers, so we have this
variable to allow the headers from that base directory to be found when
compiling driver sources. Should be appended to using ``+=`` rather than
overwritten using ``=``. The values appended should be meson include
objects got using the ``include_directories()`` function. For example:
.. code-block:: python
includes += include_directories('base')
name
As above, though note that each driver class can define it's own naming
scheme for the resulting ``.so`` files.
objs
As above, generally used for the contents of the ``base`` directory.
pkgconfig_extra_libs
**Default Value = []**
This variable is used to pass additional library link flags through to
the DPDK pkgconfig file generated, for example, to track any additional
libraries that may need to be linked into the build - especially when
using static libraries. Anything added here will be appended to the end
of the ``pkgconfig --libs`` output.
sources [mandatory]
As above
version
As above