:link_to_translation:`zh_CN:[中文]`
The esp-idf-kconfig package that ESP-IDF uses is based on kconfiglib, which is a Python extension to the Kconfig system. Kconfig provides a compile-time project configuration mechanism and offers configuration options of several types (e.g., integers, strings, and boolens). Kconfig files specify dependencies between options, default values of options, the way options are grouped together, etc.
For the full list of available features, please see Kconfig and kconfiglib extentions.
Application developers can open a terminal-based project configuration menu with the idf.py menuconfig
build target.
After being updated, this configuration is saved in the sdkconfig
file under the project root directory. Based on sdkconfig
, application build targets will generate the sdkconfig.h
file under the build directory, and will make the sdkconfig
options available to the project build system and source files.
In some cases, for example, when the sdkconfig
file is under revision control, it may be inconvenient for the build system to change the sdkconfig
file. The build system offers a solution to prevent it from happening, which is to create the sdkconfig.defaults
file. This file is never touched by the build system, and can be created manually or automatically. It contains all the options which matter to the given application and are different from the default ones. The format is the same as that of the sdkconfig
file. sdkconfig.defaults
can be created manually when one remembers all the changed configuration, or it can be generated automatically by running the idf.py save-defconfig
command.
Once sdkconfig.defaults
is created, sdkconfig
can be deleted or added to the ignore list of the revision control system (e.g., the .gitignore
file for git
). Project build targets will automatically create the sdkconfig
file, populate it with the settings from the sdkconfig.defaults
file, and configure the rest of the settings to their default values. Note that during the build process, settings from sdkconfig.defaults
will not override those already in sdkconfig
. For more information, see :ref:`custom-sdkconfig-defaults`.
Format rules for Kconfig files are as follows:
- Option names in any menus should have consistent prefixes. The prefix currently should have at least 3 characters.
- The unit of indentation should be 4 spaces. All sub-items belonging to a parent item are indented by one level deeper. For example,
menu
is indented by 0 spaces,config
menu
by 4 spaces,help
inconfig
by 8 spaces, and the text underhelp
by 12 spaces. - No trailing spaces are allowed at the end of the lines.
- The maximum length of options is 40 characters.
- The maximum length of lines is 120 characters.
Note
The help
section of each config in the menu is treated as reStructuredText to generate the reference documentation for each option.
tools/ci/check_kconfigs.py
is provided for checking Kconfig files against the above format rules. The checker checks all Kconfig and Kconfig.projbuild
files in the ESP-IDF directory, and generates a new file with suffix .new
with some suggestions about how to fix issues (if there are any). Please note that the checker cannot correct all format issues and the responsibility of the developer is to final check and make corrections in order to pass the tests. For example, indentations will be corrected if there isn't any misleading formatting, but it cannot come up with a common prefix for options inside a menu.
The standard Kconfig tools ignore unknown options in sdkconfig
. So if a developer has custom settings for options which are renamed in newer ESP-IDF releases, then the given setting for the option would be silently ignored. Therefore, several features have been adopted to avoid this:
kconfgen
is used by the tool chain to pre-processsdkconfig
files before anything else. For example,menuconfig
would read them, so the settings for old options will be kept and not ignored.kconfgen
recursively finds allsdkconfig.rename
files in ESP-IDF directory which contain old and newKconfig
option names. Old options are replaced by new ones in thesdkconfig
file. Renames that should only appear for a single target can be placed in a target-specific rename filesdkconfig.rename.TARGET
, whereTARGET
is the target name, e.g.sdkconfig.rename.esp32s2
.kconfgen
post-processessdkconfig
files and generates all build outputs (sdkconfig.h
,sdkconfig.cmake
, andauto.conf
) by adding a list of compatibility statements, i.e., the values of old options are set for new options after modification. If users still use old options in their code, this will prevent it from breaking.- :ref:`configuration-deprecated-options` are automatically generated by
kconfgen
.
Subsequent sections contain the list of available ESP-IDF options automatically generated from Kconfig files. Note that due to dependencies between options, some options listed here may not be visible by default in menuconfig
.
By convention, all option names are upper-case letters with underscores. When Kconfig generates sdkconfig
and sdkconfig.h
files, option names are prefixed with CONFIG_
. So if an option ENABLE_FOO
is defined in a Kconfig file and selected in menuconfig
, then the sdkconfig
and sdkconfig.h
files will have CONFIG_ENABLE_FOO
defined. In the following sections, option names are also prefixed with CONFIG_
, same as in the source code.
.. include-build-file:: inc/kconfig.inc