260 lines
9.6 KiB
ReStructuredText
260 lines
9.6 KiB
ReStructuredText
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.. _modules:
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Modules (External projects)
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############################
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Zephyr relies on the source code of several externally maintained projects in
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order to avoid reinventing the wheel and to reuse as much well-established,
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mature code as possible when it makes sense. In the context of Zephyr's build
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system those are called *modules*. These modules must be integrated with the
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Zephyr build system, as described in more detail in other sections on
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this page.
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Zephyr depends on several categories of modules, including:
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- Debugger integration
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- Silicon vendor Hardware Abstraction Layers (HALs)
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- Cryptography libraries
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- File Systems
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- Inter-Process Communication (IPC) libraries
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The build system variable :makevar:`ZEPHYR_MODULES` is a `CMake list`_ of
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absolute paths to the directories containing Zephyr modules. These modules
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contain :file:`CMakeLists.txt` and :file:`Kconfig` files describing how to
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build and configure them, respectively. Module :file:`CMakeLists.txt` files are
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added to the build using CMake's `add_subdirectory()`_ command, and the
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:file:`Kconfig` files are included in the build's Kconfig menu tree.
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If you have :ref:`west <west>` installed, you don't need to worry about how
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this variable is defined unless you are adding a new module. The build system
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knows how to use west to set :makevar:`ZEPHYR_MODULES`. You can add additional
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modules to this list by setting the :makevar:`ZEPHYR_EXTRA_MODULES` CMake
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variable. This can be useful if you want to keep the list of modules found with
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west and also add your own.
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See the section about :ref:`west-multi-repo` for more details.
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Finally, you can also specify the list of modules yourself in various ways, or
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not use modules at all if your application doesn't need them.
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Module Inclusion
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****************
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.. _modules_using_west:
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Using West
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==========
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If west is installed and :makevar:`ZEPHYR_MODULES` is not already set, the
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build system finds all the modules in your :term:`west installation` and uses
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those. It does this by running :ref:`west list <west-multi-repo-misc>` to get
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the paths of all the projects in the installation, then filters the results to
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just those projects which have the necessary module metadata files.
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Each project in the ``west list`` output is tested like this:
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- If the project contains a file named :file:`zephyr/module.yml`, then
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its contents should look like this:
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.. code-block:: yaml
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build:
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cmake: <cmake-directory>
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kconfig: <directory>/Kconfig
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The ``cmake: <cmake-directory>`` part specifies that
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:file:`<cmake-directory>` contains the :file:`CMakeLists.txt` to use. The
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``kconfig: <directory>/Kconfig`` part specifies the Kconfig file to use.
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Neither is required: ``cmake`` defaults to ``zephyr``, and ``kconfig``
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defaults to ``zephyr/Kconfig``.
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Here is an example :file:`module.yml` file referring to
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:file:`CMakeLists.txt` and :file:`Kconfig` files in the root directory of the
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module:
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.. code-block:: yaml
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build:
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cmake: .
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kconfig: Kconfig
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- Otherwise (i.e. if the project has no :file:`zephyr/module.yml`), the
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build system looks for :file:`zephyr/CMakeLists.txt` and
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:file:`zephyr/Kconfig` files in the project. If both are present, the project
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is considered a module, and those files will be added to the build.
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- If neither of those checks succeed, the project is not considered a module,
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and is not added to :makevar:`ZEPHYR_MODULES`.
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Without West
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============
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If you don't have west installed or don't want the build system to use it to
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find Zephyr modules, you can set :makevar:`ZEPHYR_MODULES` yourself using one
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of the following options. Each of the directories in the list must contain
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either a :file:`zephyr/module.yml` file or the files
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:file:`zephyr/CMakeLists.txt` and :file:`Kconfig`, as described in the previous
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section.
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#. At the CMake command line, like this:
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.. code-block:: console
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cmake -DZEPHYR_MODULES=<path-to-module1>[;<path-to-module2>[...]] ...
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#. At the top of your application's top level :file:`CMakeLists.txt`, like this:
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.. code-block:: cmake
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set(ZEPHYR_MODULES <path-to-module1> <path-to-module2> [...])
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include($ENV{ZEPHYR_BASE}/cmake/app/boilerplate.cmake NO_POLICY_SCOPE)
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If you choose this option, make sure to set the variable **before** including
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the boilerplate file, as shown above.
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#. In a separate CMake script which is pre-loaded to populate the CMake cache,
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like this:
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.. code-block:: cmake
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# Put this in a file with a name like "zephyr-modules.cmake"
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set(ZEPHYR_MODULES <path-to-module1> <path-to-module2>
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CACHE STRING "pre-cached modules")
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You can tell the build system to use this file by adding ``-C
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zephyr-modules.cmake`` to your CMake command line.
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Not using modules
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=================
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If you don't have west installed and don't specify :makevar:`ZEPHYR_MODULES`
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yourself, then no additional modules are added to the build. You will still be
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able to build any applications that don't require code or Kconfig options
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defined in an external repository.
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.. _submitting_new_modules:
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Submitting changes to modules
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******************************
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When submitting new or making changes to existing modules the main repository
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Zephyr needs a reference to the changes to be able to verify the changes. In the
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main tree this is done using revisions. For code that is already merged and part
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of the tree we use the commit hash, a tag, or a branch name. For pull requests
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however, we require specifying the pull request number in the revision field to
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allow building the Zephyr main tree with the changes submitted to the
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module.
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To avoid merging changes to master with pull request information, the pull
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request should be marked as ``DNM`` (Do Not Merge) or preferably a draft pull
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request to make sure it is not merged by mistake and to allow for the module to
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be merged first and be assigned a permanent commit hash. Once the module is
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merged, the revision will need to be changed either by the submitter or by the
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maintainer to the commit hash of the module which reflects the changes.
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Note that multiple and dependent changes to different modules can be submitted
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using exactly the same process. In this case you will change multiple entries of
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all modules that have a pull request against them.
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Submitting a new module
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========================
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Requirements
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-------------
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Modules to be included in the default manifest of the Zephyr project need to
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provide functionality or features endorsed and approved by the project technical
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steering committee and should follow the project licensing and
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:ref:`contribute_guidelines`.
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A request for a new module should be initialized using an RFC issue in the
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Zephyr project issue tracking system with details about the module and how it
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integrates into the project. If the request is approved, a new repository will
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created by the project team and initialized with basic information that would
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allow submitting code to the module project following the project contribution
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guidelines.
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All modules should be hosted in repositories under the Zephyr organization. The
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manifest should only point to repositories maintained under the Zephyr project.
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If a module is maintained as a fork of another project on Github, the Zephyr module
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related files and changes in relation to upstream need to be maintained in a
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special branch named ``zephyr``.
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Process
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-------
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Follow the following steps to request a new module:
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#. Use `GitHub issues`_ to open an issue with details about the module to be
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created
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#. Propose a name for the repository to be created under the Zephyr project
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organization on Github.
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#. Maintainers from the Zephyr project will create the repository and initialize
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it. You will be added as a collaborator in the new repository.
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#. Submit the module content (code) to the new repository following the
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guidelines described :ref:`here <modules_using_west>`.
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#. Add a new entry to the :zephyr_file:`west.yml` with the following
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information:
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.. code-block:: console
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- name: <name of repository>
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path: <path to where the repository should be cloned>
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revision: <ref pointer to module pull request>
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For example, to add *my_module* to the manifest:
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.. code-block:: console
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- name: my_module
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path: modules/lib/my_module
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revision: pull/23/head
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Where 23 in the example above indicated the pull request number submitted to the
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*my_module* repository. Once the module changes are reviewed and merged, the
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revision needs to be changed to the commit hash from the module repository.
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.. _changes_to_existing_module:
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Changes to existing modules
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===========================
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#. Submit the changes using a pull request to an existing repository following
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the :ref:`contribution guidelines <contribute_guidelines>`.
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#. Submit a pull request changing the entry referencing the module into the
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:zephyr_file:`west.yml` of the main Zephyr tree with the following
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information:
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.. code-block:: console
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- name: <name of repository>
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path: <path to where the repository should be cloned>
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revision: <ref pointer to module pull request>
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For example, to add *my_module* to the manifest:
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.. code-block:: console
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- name: my_module
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path: modules/lib/my_module
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revision: pull/23/head
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Where 23 in the example above indicated the pull request number submitted to the
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*my_module* repository. Once the module changes are reviewed and merged, the
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revision needs to be changed to the commit hash from the module repository.
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.. _CMake list: https://cmake.org/cmake/help/latest/manual/cmake-language.7.html#lists
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.. _add_subdirectory(): https://cmake.org/cmake/help/latest/command/add_subdirectory.html
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.. _GitHub issues: https://github.com/zephyrproject-rtos/zephyr/issues
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