+.. SPDX-License-Identifier: BSD-3-Clause
+ Copyright 2018 The DPDK contributors
+
.. _coding_style:
DPDK Coding Style
.. note::
The above is recommendation, and not a hard limit.
- However, it is expected that the recommendations should be followed in all but the rarest situations.
+ Generally, line lengths up to 100 characters are acceptable in the code.
C Comment Style
---------------
License Header
~~~~~~~~~~~~~~
-Each file should begin with a special comment containing the appropriate copyright and license for the file.
-Generally this is the BSD License, except for code for Linux Kernel modules.
+Each file must begin with a special comment containing the
+`Software Package Data Exchange (SPDX) License Identifier <https://spdx.org/using-spdx-license-identifier>`_.
+
+Generally this is the BSD License, except for code granted special exceptions.
+The SPDX licences identifier is sufficient, a file should not contain
+an additional text version of the license (boilerplate).
+
After any copyright header, a blank line should be left before any other contents, e.g. include statements in a C file.
C Preprocessor Directives
Conditional Compilation
~~~~~~~~~~~~~~~~~~~~~~~
+.. note::
+
+ Conditional compilation should be used only when absolutely necessary,
+ as it increases the number of target binaries that need to be built and tested.
+ See below for details of some utility macros/defines available
+ to allow ifdefs/macros to be replaced by C conditional in some cases.
+
+Some high-level guidelines on the use of conditional compilation:
+
+* If code can compile on all platforms/systems,
+ but cannot run on some due to lack of support,
+ then regular C conditionals, as described in the next section,
+ should be used instead of conditional compilation.
+* If the code in question cannot compile on all systems,
+ but constitutes only a small fragment of a file,
+ then conditional compilation should be used, as described in this section.
+* If the code for conditional compilation implements an interface in an OS
+ or platform-specific way, then create a file for each OS or platform
+ and select the appropriate file using the Meson build system.
+ In most cases, these environment-specific files should be created inside the EAL library,
+ rather than having each library implement its own abstraction layer.
+
+Additional style guidance for the use of conditional compilation macros:
+
* When code is conditionally compiled using ``#ifdef`` or ``#if``, a comment may be added following the matching
``#endif`` or ``#else`` to permit the reader to easily discern where conditionally compiled code regions end.
* This comment should be used only for (subjectively) long regions, regions greater than 20 lines, or where a series of nested ``#ifdef``'s may be confusing to the reader.
/* Or here. */
#endif /* !COMPAT_43 */
-.. note::
+Defines to Avoid Conditional Compilation
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+In many cases in DPDK, one wants to run code based on
+the target platform, or runtime environment.
+While this can be done using the conditional compilation directives,
+e.g. ``#ifdef RTE_EXEC_ENV_LINUX``, present in DPDK for many releases,
+this can also be done in many cases using regular ``if`` statements
+and the following defines:
+
+* ``RTE_ENV_FREEBSD``, ``RTE_ENV_LINUX``, ``RTE_ENV_WINDOWS`` -
+ these define ids for each operating system environment.
+* ``RTE_EXEC_ENV`` - this defines the id of the current environment,
+ i.e. one of the items in list above.
+* ``RTE_EXEC_ENV_IS_FREEBSD``, ``RTE_EXEC_ENV_IS_LINUX``, ``RTE_EXEC_ENV_IS_WINDOWS`` -
+ 0/1 values indicating if the current environment is that specified,
+ shortcuts for checking e.g. ``RTE_EXEC_ENV == RTE_ENV_WINDOWS``
+
+Examples of use:
+
+.. code-block:: c
+
+ /* report a unit tests as unsupported on Windows */
+ if (RTE_EXEC_ENV_IS_WINDOWS)
+ return TEST_SKIPPED;
+
+ /* set different default values depending on OS Environment */
+ switch (RTE_EXEC_ENV) {
+ case RTE_ENV_FREEBSD:
+ default = x;
+ break;
+ case RTE_ENV_LINUX:
+ default = y;
+ break;
+ case RTE_ENV_WINDOWS:
+ default = z;
+ break;
+ }
- Conditional compilation should be used only when absolutely necessary, as it increases the number of target binaries that need to be built and tested.
C Types
-------
* Use of the structures should be by separate variable declarations and those declarations must be extern if they are declared in a header file.
* Externally visible structure definitions should have the structure name prefixed by ``rte_`` to avoid namespace collisions.
+.. note::
+
+ Uses of ``bool`` in structures are not preferred as is wastes space and
+ it's also not clear as to what type size the bool is. A preferred use of
+ ``bool`` is mainly as a return type from functions that return true/false,
+ and maybe local variable functions.
+
+ Ref: `LKML <https://lkml.org/lkml/2017/11/21/384>`_
+
Queues
~~~~~~
DPDK also provides an optimized way to store elements in lockless rings.
This should be used in all data-path code, when there are several consumer and/or producers to avoid locking for concurrent access.
+Naming
+------
+
+For symbol names and documentation, new usage of
+'master / slave' (or 'slave' independent of 'master') and 'blacklist /
+whitelist' is not allowed.
+
+Recommended replacements for 'master / slave' are:
+ '{primary,main} / {secondary,replica,subordinate}'
+ '{initiator,requester} / {target,responder}'
+ '{controller,host} / {device,worker,proxy}'
+ 'leader / follower'
+ 'director / performer'
+
+Recommended replacements for 'blacklist/whitelist' are:
+ 'denylist / allowlist'
+ 'blocklist / passlist'
+
+Exceptions for introducing new usage is to maintain compatibility
+with an existing (as of 2020) hardware or protocol
+specification that mandates those terms.
+
+
Typedefs
~~~~~~~~
typedef int (lcore_function_t)(void *);
/* launch a function of lcore_function_t type */
- int rte_eal_remote_launch(lcore_function_t *f, void *arg, unsigned slave_id);
+ int rte_eal_remote_launch(lcore_function_t *f, void *arg, unsigned worker_id);
C Indentation
~~~~~~~~~~~~
* Functions which create objects, or allocate memory, should return pointer types, and NULL on error.
- The error type should be indicated may setting the variable ``rte_errno`` appropriately.
+ The error type should be indicated by setting the variable ``rte_errno`` appropriately.
* Functions which work on bursts of packets, such as RX-like or TX-like functions, should return the number of packets handled.
* Other functions returning int should generally behave like system calls:
returning 0 on success and -1 on error, setting ``rte_errno`` to indicate the specific type of error.
* is DEBUG) */
rte_log_set_level(my_logtype2, RTE_LOG_NOTICE);
- /* enable all PMD logs (whose identifier string starts with "pmd") */
- rte_log_set_level_regexp("pmd.*", RTE_LOG_DEBUG);
+ /* enable all PMD logs (whose identifier string starts with "pmd.") */
+ rte_log_set_level_pattern("pmd.*", RTE_LOG_DEBUG);
/* log in debug level */
rte_log_set_global_level(RTE_LOG_DEBUG);
- RTE_LOG(DEBUG, my_logtype1, "this is is a debug level message\n");
- RTE_LOG(INFO, my_logtype1, "this is is a info level message\n");
- RTE_LOG(WARNING, my_logtype1, "this is is a warning level message\n");
- RTE_LOG(WARNING, my_logtype2, "this is is a debug level message (not displayed)\n");
+ RTE_LOG(DEBUG, my_logtype1, "this is a debug level message\n");
+ RTE_LOG(INFO, my_logtype1, "this is a info level message\n");
+ RTE_LOG(WARNING, my_logtype1, "this is a warning level message\n");
+ RTE_LOG(WARNING, my_logtype2, "this is a debug level message (not displayed)\n");
/* log in info level */
rte_log_set_global_level(RTE_LOG_INFO);
/* NOTREACHED */
}
+Dynamic Logging
+---------------
-Python Code
------------
+DPDK provides infrastructure to perform logging during runtime. This is very
+useful for enabling debug output without recompilation. To enable or disable
+logging of a particular topic, the ``--log-level`` parameter can be provided
+to EAL, which will change the log level. DPDK code can register topics,
+which allows the user to adjust the log verbosity for that specific topic.
-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/>`_.
+In general, the naming scheme is as follows: ``type.section.name``
-The ``pep8`` tool can be used for testing compliance with the guidelines.
+ * Type is the type of component, where ``lib``, ``pmd``, ``bus`` and ``user``
+ are the common options.
+ * Section refers to a specific area, for example a poll-mode-driver for an
+ ethernet device would use ``pmd.net``, while an eventdev PMD uses
+ ``pmd.event``.
+ * The name identifies the individual item that the log applies to.
+ The name section must align with
+ the directory that the PMD code resides. See examples below for clarity.
-Integrating with the Build System
----------------------------------
+Examples:
-DPDK supports being built in two different ways:
+ * The virtio network PMD in ``drivers/net/virtio`` uses ``pmd.net.virtio``
+ * The eventdev software poll mode driver in ``drivers/event/sw`` uses ``pmd.event.sw``
+ * The octeontx mempool driver in ``drivers/mempool/octeontx`` uses ``pmd.mempool.octeontx``
+ * The DPDK hash library in ``lib/hash`` uses ``lib.hash``
-* using ``make`` - or more specifically "GNU make", i.e. ``gmake`` on FreeBSD
-* using the tools ``meson`` and ``ninja``
+Specializations
+~~~~~~~~~~~~~~~
-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.
+In addition to the above logging topic, any PMD or library can further split
+logging output by using "specializations". A specialization could be the
+difference between initialization code, and logs of events that occur at runtime.
-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.
+An example could be the initialization log messages getting one
+specialization, while another specialization handles mailbox command logging.
+Each PMD, library or component can create as many specializations as required.
-Makefile Contents
-~~~~~~~~~~~~~~~~~
+A specialization looks like this:
-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.
+ * Initialization output: ``type.section.name.init``
+ * PF/VF mailbox output: ``type.section.name.mbox``
-.. code-block:: none
+A real world example is the i40e poll mode driver which exposes two
+specializations, one for initialization ``pmd.net.i40e.init`` and the other for
+the remaining driver logs ``pmd.net.i40e.driver``.
- # pull in basic DPDK definitions, including whether library is to be
- # built or not
- include $(RTE_SDK)/mk/rte.vars.mk
+Note that specializations have no formatting rules, but please follow
+a precedent if one exists. In order to see all current log topics and
+specializations, run the ``app/test`` binary, and use the ``dump_log_types``
- # library name
- LIB = librte_<name>.a
+Python Code
+-----------
+
+All Python code should 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.
- # any library cflags needed. Generally add "-O3 $(WERROR_FLAGS)"
- CFLAGS += -O3
- CFLAGS += $(WERROR_FLAGS)
+Integrating with the Build System
+---------------------------------
- # the symbol version information for the library, and .so version
- EXPORT_MAP := rte_<name>_version.map
- LIBABIVER := 1
+DPDK is built using the tools ``meson`` and ``ninja``.
- # all source filenames are stored in SRCS-y
- SRCS-$(CONFIG_RTE_LIBRTE_<NAME>) += rte_<name>.c
+.. note::
- # install includes
- SYMLINK-$(CONFIG_RTE_LIBRTE_<NAME>)-include += rte_<name>.h
+ In order to catch possible issues as soon as possible,
+ it is recommended that developers build DPDK in "developer mode" to enable additional checks.
+ By default, this mode is enabled if the build is being done from a git checkout,
+ but the mode can be manually enabled/disabled using the
+ ``developer_mode`` meson configuration option.
- # pull in rules to build the library
- include $(RTE_SDK)/mk/rte.lib.mk
+Therefore all new component additions should include a ``meson.build`` file,
+and should be added to the component lists in the ``meson.build`` files in the
+relevant top-level directory:
+either ``lib`` directory or a ``driver`` subdirectory.
Meson Build File Contents - Libraries
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. code-block:: python
sources = files('file1.c', ...)
- headers = files('file1.c', ...)
+ headers = files('file1.h', ...)
-The will build based on a number of conventions and assumptions within the DPDK
+This 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.
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:
+ environment. When set to "false" the ``reason`` value, explained below, should
+ also be set to explain to the user why the component is not being built.
+ A simple example of use would be:
.. code-block:: python
- if host_machine.system() != 'linux'
+ if not is_linux
build = false
+ reason = 'only supported on Linux'
endif
installed to $PREFIX/include when ``ninja install`` is run. As with
source files, these should be specified using the meson ``files()``
function.
+ When ``check_includes`` build option is set to ``true``, each header file
+ has additional checks performed on it, for example to ensure that it is
+ not missing any include statements for dependent headers.
+ For header files which are public, but only included indirectly in
+ applications, these checks can be skipped by using the ``indirect_headers``
+ variable rather than ``headers``.
+
+indirect_headers
+ **Default Value = []**.
+ As with ``headers`` option above, except that the files are not checked
+ for all needed include files as part of a DPDK build when
+ ``check_includes`` is set to ``true``.
includes:
**Default Value = []**.
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
+ sources are stored in a directory ``lib/xyz``, this value should
never be needed for new libraries.
.. note::
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.
+reason
+ **Default Value = '<unknown reason>'**.
+ This variable should be used when a library is not to be built i.e. when
+ ``build`` is set to "false", to specify the reason why a library will not be
+ built. For missing dependencies this should be of the form
+ ``'missing dependency, "libname"'``.
+
+use_function_versioning
+ **Default Value = false**.
+ Specifies if the library in question has ABI versioned functions. If it
+ has, this value should be set to ensure that the C files are compiled
+ twice with suitable parameters for each of shared or static library
+ builds.
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.
using static libraries. Anything added here will be appended to the end
of the ``pkgconfig --libs`` output.
+reason
+ As above.
+
sources [mandatory]
As above
+headers
+ As above
+
version
As above
+
+
+Meson Coding Style
+------------------
+
+The following guidelines apply to the build system code in meson.build files in DPDK.
+
+* Indentation should be using 4 spaces, no hard tabs.
+
+* Line continuations should be doubly-indented to ensure visible difference from normal indentation.
+ Any line continuations beyond the first may be singly indented to avoid large amounts of indentation.
+
+* Where a line is split in the middle of a statement, e.g. a multiline `if` statement,
+ brackets should be used in preference to escaping the line break.
+
+Example::
+
+ if (condition1 and condition2 # line breaks inside () need no escaping
+ and condition3 and condition4)
+ x = y
+ endif
+
+* Lists of files or components must be alphabetical unless doing so would cause errors.
+
+* Two formats are supported for lists of files or list of components:
+
+ * For a small number of list entries, generally 3 or fewer, all elements may be put on a single line.
+ In this case, the opening and closing braces of the list must be on the same line as the list items.
+ No trailing comma is put on the final list entry.
+ * For lists with more than 3 items,
+ it is recommended that the lists be put in the files with a *single* entry per line.
+ In this case, the opening brace, or ``files`` function call must be on a line on its own,
+ and the closing brace must similarly be on a line on its own at the end.
+ To help with readability of nested sublists, the closing brace should be dedented to appear
+ at the same level as the opening braced statement.
+ The final list entry must have a trailing comma,
+ so that adding a new entry to the list never modifies any other line in the list.
+
+Examples::
+
+ sources = files('file1.c', 'file2.c')
+
+ subdirs = ['dir1', 'dir2']
+
+ headers = files(
+ 'header1.c',
+ 'header2.c',
+ 'header3.c', # always include trailing comma
+ ) # closing brace at indent level of opening brace
+
+ components = [
+ 'comp1',
+ 'comp2',
+ ...
+ 'compN',
+ ]
git.droids-corp.org / dpdk.git / blobdiff