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How to: Kconfig

This article will demonstrate how to use Kconfig in your project.

info

Kconfig is a system inherited from the Linux kernel to the Zephyr project. It allows the definition of build-time options (also called symbols), their types, constraints, and relationships.

Custom Options​

You can define your custom Kconfig option in your application by creating the Kconfig file in the application root directory.

In the Kconfig file, you can create a boolean yes/no option using this template:

menu "Application"

config APP_FOO
    bool "Enable bar"
    default y

endmenu

menu "Zephyr Kernel"
source "Kconfig.zephyr"
endmenu

This will create a menu tree called Application. The tree will have one option APP_FOO, which is enabled by default, and can be disabled in your prj.conf file:

CONFIG_APP_FOO=n

When pre-processing all Kconfig options, this will result in one of these macros:

/* When CONFIG_APP_FOO=y */
#define CONFIG_APP_FOO 1

/* When CONFIG_APP_FOO=n */
#define CONFIG_APP_FOO 0
tip

You can debug the generated Kconfig options by looking into the file build/zephyr/include/autoconf.h. This file is automatically injected into all source/header files.

References​

If you need more details on Kconfig, see the Zephyr Kconfig documentation: https://docs.zephyrproject.org/latest/build/kconfig/index.html