mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-05 02:51:00 +00:00
5579ce747d
This is not needed now that CONFIG_SYS_TARGET_NAME is correctly determined
when scanning Kconfig.
This reverts commit 25b8acee2e
.
Signed-off-by: Simon Glass <sjg@chromium.org>
Suggested-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
151 lines
5.6 KiB
Text
151 lines
5.6 KiB
Text
Kconfig in U-Boot
|
|
=================
|
|
|
|
This document describes the configuration infrastructure of U-Boot.
|
|
|
|
The conventional configuration was replaced by Kconfig at v2014.10-rc1 release.
|
|
|
|
|
|
Language Specification
|
|
----------------------
|
|
|
|
Kconfig originates in Linux Kernel.
|
|
See the file "Documentation/kbuild/kconfig*.txt" in your Linux Kernel
|
|
source directory for a basic specification of Kconfig.
|
|
|
|
|
|
Difference from Linux's Kconfig
|
|
-------------------------------
|
|
|
|
Here are some worth-mentioning configuration targets.
|
|
|
|
- silentoldconfig
|
|
|
|
This target updates .config, include/generated/autoconf.h and
|
|
include/configs/* as in Linux. In U-Boot, it also does the following
|
|
for the compatibility with the old configuration system:
|
|
|
|
* create a symbolic link "arch/${ARCH}/include/asm/arch" pointing to
|
|
the SoC/CPU specific header directory
|
|
* create include/config.h
|
|
* create include/autoconf.mk
|
|
* create spl/include/autoconf.mk (SPL and TPL only)
|
|
* create tpl/include/autoconf.mk (TPL only)
|
|
|
|
If we could completely switch to Kconfig in a long run
|
|
(i.e. remove all the include/configs/*.h), those additional processings
|
|
above would be removed.
|
|
|
|
- defconfig
|
|
|
|
In U-Boot, "make defconfig" is a shorthand of "make sandbox_defconfig"
|
|
|
|
- <board>_defconfig
|
|
|
|
Now it works as in Linux.
|
|
The prefixes such as "+S:" in *_defconfig are deprecated.
|
|
You can simply remove the prefixes. Do not add them for new boards.
|
|
|
|
- <board>_config
|
|
|
|
This does not exist in Linux's Kconfig.
|
|
"make <board>_config" works the same as "make <board>_defconfig".
|
|
Prior to Kconfig, in U-Boot, "make <board>_config" was used for the
|
|
configuration. It is still supported for backward compatibility, so
|
|
we do not need to update the distro recipes.
|
|
|
|
|
|
The other configuration targets work as in Linux Kernel.
|
|
|
|
|
|
Migration steps to Kconfig
|
|
--------------------------
|
|
|
|
Prior to Kconfig, the C preprocessor based board configuration had been used
|
|
in U-Boot.
|
|
|
|
Although Kconfig was introduced and some configs have been moved to Kconfig,
|
|
many of configs are still defined in C header files. It will take a very
|
|
long term to move all of them to Kconfig. In the interim, the two different
|
|
configuration infrastructures should coexist.
|
|
The configuration files are generated by both Kconfig and the old preprocessor
|
|
based configuration as follows:
|
|
|
|
Configuration files for use in C sources
|
|
- include/generated/autoconf.h (generated by Kconfig for Normal)
|
|
- include/configs/<board>.h (exists for all boards)
|
|
|
|
Configuration file for use in makefiles
|
|
- include/config/auto.conf (generated by Kconfig)
|
|
- include/autoconf.mk (generated by the old config for Normal)
|
|
- spl/include/autoconfig.mk (generated by the old config for SPL)
|
|
- tpl/include/autoconfig.mk (generated by the old config for TPL)
|
|
|
|
When adding a new CONFIG macro, it is highly recommended to add it to Kconfig
|
|
rather than to a header file.
|
|
|
|
|
|
Conversion from boards.cfg to Kconfig
|
|
-------------------------------------
|
|
|
|
Prior to Kconfig, boards.cfg was a primary database that contained Arch, CPU,
|
|
SoC, etc. of all the supported boards. It was deleted when switching to
|
|
Kconfig. Each field of boards.cfg was converted as follows:
|
|
|
|
Status -> "S:" entry of MAINTAINERS
|
|
Arch -> CONFIG_SYS_ARCH defined by Kconfig
|
|
CPU -> CONFIG_SYS_CPU defined by Kconfig
|
|
SoC -> CONFIG_SYS_SOC defined by Kconfig
|
|
Vendor -> CONFIG_SYS_VENDOR defined by Kconfig
|
|
Board -> CONFIG_SYS_BOARD defined by Kconfig
|
|
Target -> File name of defconfig (configs/<target>_defconfig)
|
|
Maintainers -> "M:" entry of MAINTAINERS
|
|
|
|
|
|
Tips to add/remove boards
|
|
-------------------------
|
|
|
|
When adding a new board, the following steps are generally needed:
|
|
|
|
[1] Add a header file include/configs/<target>.h
|
|
[2] Make sure to define necessary CONFIG_SYS_* in Kconfig:
|
|
Define CONFIG_SYS_CPU="cpu" to compile arch/<arch>/cpu/<cpu>
|
|
Define CONFIG_SYS_SOC="soc" to compile arch/<arch>/cpu/<cpu>/<soc>
|
|
Define CONFIG_SYS_VENDOR="vendor" to compile board/<vendor>/common/*
|
|
and board/<vendor>/<board>/*
|
|
Define CONFIG_SYS_BOARD="board" to compile board/<board>/*
|
|
(or board/<vendor>/<board>/* if CONFIG_SYS_VENDOR is defined)
|
|
Define CONFIG_SYS_CONFIG_NAME="target" to include
|
|
include/configs/<target>.h
|
|
[3] Add a new entry to the board select menu in Kconfig.
|
|
The board select menu is located in arch/<arch>/Kconfig or
|
|
arch/<arch>/*/Kconfig.
|
|
[4] Add a MAINTAINERS file
|
|
It is generally placed at board/<board>/MAINTAINERS or
|
|
board/<vendor>/<board>/MAINTAINERS
|
|
[5] Add configs/<target>_defconfig
|
|
|
|
When removing an obsolete board, the following steps are generally needed:
|
|
|
|
[1] Remove configs/<target>_defconfig
|
|
[2] Remove include/configs/<target>.h if it is not used by any other boards
|
|
[3] Remove board/<vendor>/<board>/* or board/<board>/* if it is not used
|
|
by any other boards
|
|
[4] Update MAINTAINERS if necessary
|
|
[5] Remove the unused entry from the board select menu in Kconfig
|
|
[6] Add an entry to doc/README.scrapyard
|
|
|
|
|
|
TODO
|
|
----
|
|
|
|
- In the pre-Kconfig, a single board had multiple entries in the boards.cfg
|
|
file with differences in the option fields. The corresponding defconfig
|
|
files were auto-generated when switching to Kconfig. Now we have too many
|
|
defconfig files compared with the number of the supported boards. It is
|
|
recommended to have only one defconfig per board and allow users to select
|
|
the config options.
|
|
|
|
- Move the config macros in header files to Kconfig. When we move at least
|
|
macros used in makefiles, we can drop include/autoconfig.mk, which makes
|
|
the build scripts much simpler.
|