243 lines
8.2 KiB
ReStructuredText
243 lines
8.2 KiB
ReStructuredText
.. _microkernel_apps:
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How to Develop Microkernel Applications
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#######################################
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Microkernel applications are composed of .c and . h files that are
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integrated with the |codename| using MDEF files, Makefiles and .conf files.
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Developing a microkernel application can be accomplished in five steps:
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#. Plan your application and take note of all microkernel objects it will
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need.
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#. Create the MDEF file for those microkernel objects.
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#. Code the application source files.
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#. Create the Makefiles to add the application's source files to the
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kernel's build system.
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#. Compile and test your application.
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The following procedures show examples of how to accomplish this.
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Before Starting the Development of a Microkernel App
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****************************************************
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Before you begin, read the :ref:`overview` and the :ref:`quick_start`.
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Then read the :ref:`collaboration_guidelines`. Finally, review
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the developers information contained in :ref:`developing_zephyr` and build a
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sample application, like :file:`hello.c`.
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Once you have completed those tasks, you should be able to answer:
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* How does the |codename| and its key objects work?
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* What is the difference between a nanokernel and a microkernel?
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* How is the |codename| built?
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* What rules and conventions must the development follow?
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If you are able to answer these questions, you can start developing your
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application.
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Creating an MDEF File
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*********************
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The :abbr:`MDEF (Microkernel DEfinitions File)` contains the configuration
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entries for the kernel's objects. Therefore, it must include all microkernel
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objects used in the C code of the application. Each line in a MDEF file
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defines one item, unless it is empty or a comment line. All lines starting
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with a ``%`` are comments.
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The contents of an MDEF file can be, for example:
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.. code-block:: console
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:linenos:
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% TASKGROUP NAME
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% =======================
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TASKGROUP ITERATIONS
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% TASK NAME PRIO ENTRY STACK GROUPS
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% ========================================================
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TASK MASTER 7 master 1024 [EXE]
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TASK PLOTTER 5 plotter 1024 [EXE]
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TASK TASK10 6 task 2048 [ITERATIONS]
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TASK TASK11 6 task 2048 [ITERATIONS]
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TASK TASK12 6 task 2048 [ITERATIONS]
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TASK TASK13 6 task 2048 [ITERATIONS]
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% FIFO NAME DEPTH WIDTH
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% =============================
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FIFO PLOTQ 200 20
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FIFO COORDQ 16 16
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FIFO SCREENQ 16 20
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% SEMA NAME
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% =============
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SEMA FINISHED
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% MUTEX NAME
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% =====================
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MUTEX PRINT
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MUTEX GRAPH
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MUTEX POPPARAM
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MUTEX PUSHPARAM
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Each object must follow a specific syntax. The object name must be an
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alphanumeric, with an alphabetical first character. Upper- and lowercase
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letters are allowed; embedded spaces are not. The convention is to give
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each object a name that is in all uppercase letters. This makes it easy to
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distinguish between object names and variable names. Finally, all names must
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be unique. A pipe cannot have the same name as a FIFO, even though they are
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different types.
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See :ref:`microkernel` for the correct syntax for the most important
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microkernel objects.
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Coding the Application's Source Files
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*************************************
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We recommend you follow the project's :ref:`coding_style` when coding your
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application. The required MDEF file can be in any folder of your
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application as long as the path is referenced in the application's Makefile.
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The application's root folder must contain a Makefile that links the
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application to the kernel; see :ref:`root_makefile` for details. Each folder
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in your source tree must have a Makefile that links the folder's
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contents with the rest of your source tree; see :ref:`source_makefile` for
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details.
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Finally, remember that your application will be compiled into the
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kernel. If all MDEF files and Makefiles are correct and in place, the build
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system links your application with the kernel. The kernel delivers binaries,
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one for each selected platform, for testing.
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.. _app_makefile:
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Creating the Makefiles for the Application
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******************************************
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This section explains how the Makefiles within the folders of your
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application link it to the kernel. The build system's Makefile will assume that
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the application's root folder has a :file:`src` folder containing all
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source files. The name of the folder can be changed to whatever name suits
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your needs. The :file:`src` folder can have as many subfolders as needed but
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all folders must contain a Makefile.
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The contents of the Makefiles can fit the needs of your application.
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However, some contents are required for a successful integration. The
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contents required in the application's Makefile at the main folder differ
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from those required in the Makefiles inside the source folders.
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For detailed information regarding the build system's Makefiles see:
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:ref:`kbuild_makefiles`.
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.. _root_makefile:
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The Application's Root Folder Makefile
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======================================
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The Makefile in the application's root folder must contain at least these
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entries:
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* :makevar:`MDEF_FILE`: The name of the application's MDEF file.
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* :makevar:`KERNEL_TYPE`: Either `nano` for nanokernel applications or
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`micro` for microkernel applications.
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* :makevar:`PLATFORM_CONFIG`: The name of the platform configuration that
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will be used as a default.
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* :makevar:`CONF_FILE`: The name of the .conf file or files of the
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application.
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* ``include ${ZEPHYR_BASE}/Makefile.inc`` This instruction adds the contents
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of the :file:`Makefile.inc` found in the kernel's root folder.
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For more information about Makefile variables see :ref:`kbuild_project`.
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Examples
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--------
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The following example shows a generic application's root folder Makefile:
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.. code-block:: make
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:linenos:
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:emphasize-lines: 4, 6
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MDEF_FILE = application.mdef
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KERNEL_TYPE = micro
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PLATFORM_CONFIG ?= basic_atom
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CONF_FILE = application_$(ARCH).conf
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include ${ZEPHYR_BASE}/Makefile.inc
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Line 4 shows how to conditionally add files. The build system replaces the
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variable ``$(ARCH)`` for each supported architecture.
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The entry in line 6 includes all entries located in :file:`Makefile.inc`
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at the kernel's root folder. The entries let the build system know that
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your application has to be included as part of the build.
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The next example comes from the kernel's code, specifically from
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:file:`samples/microkernel/apps/hello_world/Makefile`:
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.. literalinclude:: ../../samples/microkernel/apps/hello_world/Makefile
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:language: make
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:lines: 1-6
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:emphasize-lines: 1, 4
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:linenos:
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The file :file:`proj.mdef` from line 1 can be found in
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:file:`microkernel/apps/hello_world/` and contains the configuration entries
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of all microkernel objects used in the application. For more information
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regarding MDEF files see the :ref:`microkernel` documentation.
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The entry in line 4 references the files :file:`proj_arm.conf` and
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:file:`proj_x86.conf` also found at that location. Those files include the
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configuration values that differ from the default. See
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:ref:`configuration_snippets` for details.
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The Application's Source Folders Makefiles
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==========================================
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The Makefiles in the source folders add the files within the folders to the
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build system. See :ref:`makefile_conventions` for details.
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Examples
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--------
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Example 1 shows the source folder Makefile of the microkernel Hello World
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application.
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Example 1:
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.. literalinclude:: ../../samples/microkernel/apps/hello_world/src/Makefile
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:language: make
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:lines: 1-4
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:emphasize-lines: 1, 3
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:linenos:
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Line 1 allows the application's source file access to the functions included
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in the project's .h files. Line 3 adds the :file:`hello.c` to the build
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system.
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Example 2 shows the source folder Makefile of the microkernel Philosophers
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application.
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Example 2:
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.. literalinclude:: ../../samples/microkernel/apps/philosophers/src/Makefile
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:language: make
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:lines: 1-4
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:emphasize-lines: 3
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:linenos:
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Line 3 adds the :file:`phil_fiber.c` and :file:`phil_task.c` files. Multiple
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files can be added on a single line by separating them with a space.
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