.. _apps_kernel_conf: Kernel Configuration #################### The application's kernel is configured from a set of options that can be customized for application-specific purposes. Each configuration option is derived from the first source in which it is specified: a. The value specified by the application’s current configuration; that is, its :file:`.config` file. b. The value specified by the application’s default configuration; that is, its :file:`prj.conf` file. c. The value specified by the platform configuration. d. The kernel’s default value for the configuration option. .. note:: When the default platform configuration settings are sufficient for your application, a :file:`prj.conf` file is not needed. Skip ahead to :ref:`override_kernel_conf`. Procedures ********** * `define_default_kernel_conf`_ * `Overriding the Application's Default Kernel Configuration`_ The procedures that follow describe how to configure a :file:`prj.conf` file and how to configure kernel options for microkernel and nanokernel applications. For information on how to work with kernel option inter-dependencies and platform configuration-default options, see the :ref:`configuration`. .. note:: There are currently a number of experimental options not yet fully supported. .. _define_default_kernel_conf: Defining the Application's Default Kernel Configuration ======================================================= Create a :file:`prj.conf` file to define the application's default kernel configuration. This file can contain settings that override or augment platform-configuration settings. The contents of the supported platform configuration files can be viewed in :file:`~/rootDir/architectureDir/configs`. Before you begin ---------------- * Confirm Zephyr environment variables are set for each console terminal using :ref:`apps_common_procedures`. Steps ----- 1. Navigate to the :file:`appDir`, and create the :file:`prj.conf` file. Enter: .. code-block:: bash $ touch prj.conf The default name is :file:`prj.conf`. The filename must match the :option:`CONF_FILE` entry in the application :file:`Makefile`. 2. Edit the file and add the appropriate configuration entries. a) Add each configuration entry on a new line. b) Begin each entry with :option:`CONFIG_`. c) Ensure that each entry contains no spaces (including on either side of the = sign). d) Use a # followed by a space to comment a line. This example shows a comment line and a platform configuration override in the :file:`prj.conf`. .. code-block:: c # Change the number of IRQs supported by the application CONFIG_NUM_IRQS=43 3. Save and close the file. .. _override_kernel_conf: Overriding the Application's Default Kernel Configuration ========================================================= Override the application's default kernel configuration to temporarily alter the application’s configuration, perhaps to test the effect of a change. .. note:: If you want to permanently alter the configuration you should revise the :file:`.conf` file. Configure the kernel options using a menu-driven interface. While you can add entries manually, using the configuration menu is a preferred method. Before you begin ---------------- * Review the kernel configuration options available and know which ones you want to temporarily set for your application. See the :ref:`configuration` for a brief description of each option. * Be aware of any dependencies among the kernel configuration options. * Confirm an application :file:`Makefile` exists for your application. * Confirm the Zephyr environment variable is set for each console terminal; see :ref:`apps_common_procedures`. Steps ----- 1. Run the :command:`make menuconfig` rule to launch the menu-driven interface. a) In a terminal session, navigate to the application directory (:file:`~/appDir`). b) Enter the following command: .. code-block:: bash $ make menuconfig A question-based menu opens that allows you to set individual configuration options. .. image:: figures/app_kernel_conf_1.png :width: 400px :align: center :height: 375px :alt: Main Configuration Menu 2. Set kernel configuration values using the following key commands: * Use the arrow keys to navigate within any menu or list. * Press :kbd:`Enter` to select a menu item. * Type an upper case :kbd:`Y` or :kbd:`N` in the square brackets :guilabel:`[ ]` to enable or disable a kernel configuration option. * Type a numerical value in the round brackets :guilabel:`( )`. * Press :kbd:`Tab` to navigate the command menu at the bottom of the display. .. note:: When a non-default entry is selected for options that are nonnumerical, an asterisk :kbd:`*` appears between the square brackets in the display. There is nothing added added the display when you select the option's default. 3. For information about any option, select the option and tab to :guilabel:`< Help >` and press :kbd:`Enter`. Press :kbd:`Enter` to return to the menu. 4. After configuring the kernel options for your application, tab to :guilabel:`< Save >` and press :kbd:`Enter`. The following dialog opens with the :guilabel:`< Ok >` command selected: .. image:: figures/app_kernel_conf_2.png :width: 400px :align: center :height: 100px :alt: Save Configuration Dialog 5. Press :kbd:`Enter` to save the kernel configuration options to the default file name; alternatively, type a file name and press :kbd:`Enter`. Typically, you will save to the default file name unless you are experimenting with various configuration scenarios. An :file:`outdir` directory is created in the application directory. The outdir directory contains symbolic links to files under $(ZEPHYR_BASE). .. note:: At present, only a :file:`.config` file can be built. If you have saved files with different file names and want to build with one of these, change the file name to :file:`.config`. To keep your original :file:`.config`, rename it to something other than :file:`.config`. Kernel configuration files, such as the :file:`.config` file, are saved as hidden files in :file:`outdir`. To list all your kernel configuration files, enter :command:`ls -a` at the terminal prompt. The following dialog opens, displaying the file name the configuration was saved to. .. image:: figures/app_kernel_conf_3.png :width: 400px :align: center :height: 150px :alt: Saved Configuration Name Dialog 6. Press :kbd:`Enter` to return to the options menu. 7. To load any saved kernel configuration file, tab to :guilabel:`< Load >` and press :kbd:`Enter`. The following dialog opens with the :guilabel:`< Ok >` command selected: .. image:: figures/app_kernel_conf_4.png :width: 400px :align: center :height: 175px :alt: Configuration File Load Dialog 8. To load the last saved kernel configuration file, press :guilabel:`< Ok >`, or to load another saved configuration file, type the file name, then select :guilabel:`< Ok >`. 9. Press :kbd:`Enter` to load the file and return to the main menu. 10. To exit the menu configuration, tab to :guilabel:`< Exit >` and press :kbd:`Enter`. The following confirmation dialog opens with the :guilabel:`< Yes >` command selected. .. image:: figures/app_kernel_conf_5.png :width: 400px :align: center :height: 100px :alt: Exit Dialog 11. Press :kbd:`Enter` to retire the menu display and return to the console command line. **Next Steps**: For microkernel applications, go to :ref:`Creating and Configuring an MDEF File for a Microkernel Application`. For nanokernel applications, go to :ref:`apps_code_dev`.