moveconfig - Migrating and querying CONFIG options

Since Kconfig was introduced to U-Boot, we have worked on moving config options from headers to Kconfig (defconfig).

This tool intends to help this tremendous work.


You may need to install ‘python3-asteval’ for the ‘asteval’ module.


First, you must edit the Kconfig to add the menu entries for the configs you are moving.

Then run this tool giving CONFIG names you want to move. For example, if you want to move CONFIG_CMD_USB and CONFIG_TEXT_BASE, simply type as follows:


The tool walks through all the defconfig files and move the given CONFIGs.

The log is also displayed on the terminal.

The log is printed for each defconfig as follows:


<defconfig_name> is the name of the defconfig.

<action*> shows what the tool did for that defconfig. It looks like one of the following:

  • Move ‘CONFIG_… ‘ This config option was moved to the defconfig

  • CONFIG_… is not defined in Kconfig. Do nothing. The entry for this CONFIG was not found in Kconfig. The option is not defined in the config header, either. So, this case can be just skipped.

  • CONFIG_… is not defined in Kconfig (suspicious). Do nothing. This option is defined in the config header, but its entry was not found in Kconfig. There are two common cases:

    • You forgot to create an entry for the CONFIG before running this tool, or made a typo in a CONFIG passed to this tool.

    • The entry was hidden due to unmet ‘depends on’.

    The tool does not know if the result is reasonable, so please check it manually.

  • ‘CONFIG_…’ is the same as the define in Kconfig. Do nothing. The define in the config header matched the one in Kconfig. We do not need to touch it.

  • Compiler is missing. Do nothing. The compiler specified for this architecture was not found in your PATH environment. (If -e option is passed, the tool exits immediately.)

  • Failed to process. An error occurred during processing this defconfig. Skipped. (If -e option is passed, the tool exits immediately on error.)

Finally, you will be asked, Clean up headers? [y/n]:

If you say ‘y’ here, the unnecessary config defines are removed from the config headers (include/configs/*.h). It just uses the regex method, so you should not rely on it. Just in case, please do ‘git diff’ to see what happened.

How does it work?

This tool runs configuration and builds include/ for every defconfig. The config options defined in Kconfig appear in the .config file (unless they are hidden because of unmet dependency.) On the other hand, the config options defined by board headers are seen in include/ The tool looks for the specified options in both of them to decide the appropriate action for the options. If the given config option is found in the .config, but its value does not match the one from the board header, the config option in the .config is replaced with the define in the board header. Then, the .config is synced by “make savedefconfig” and the defconfig is updated with it.

For faster processing, this tool handles multi-threading. It creates separate build directories where the out-of-tree build is run. The temporary build directories are automatically created and deleted as needed. The number of threads are chosen based on the number of the CPU cores of your system although you can change it via -j (–jobs) option.


Appropriate toolchain are necessary to generate include/ for all the architectures supported by U-Boot. Most of them are available at the site, some are not provided by This tool uses the same tools as buildman, so see that tool for setup (e.g. –fetch-arch).

Tips and trips

To sync only X86 defconfigs:

./tools/ -s -d <(grep -l X86 configs/*)


grep -l X86 configs/* | ./tools/ -s -d -

To process CONFIG_CMD_FPGAD only for a subset of configs based on path match:

ls configs/{hrcon*,iocon*,strider*} | \
    ./tools/ -Cy CONFIG_CMD_FPGAD -d -

Finding boards with particular CONFIG combinations

You can use to figure out which boards have a CONFIG enabled, or which do not. To use it, first build a database:

./tools/ -b

Then you can run queries using the -f flag followed by a list of CONFIG terms. Each term is CONFIG name, with or without a tilde (~) prefix. The tool searches for boards which match the CONFIG name, or do not match if tilde is used. For example, to find boards which enabled CONFIG_SCSI but not CONFIG_BLK:

tools/ -f SCSI ~BLK
3 matches
pg_wcom_seli8_defconfig highbank_defconfig pg_wcom_expu1_defconfig

Finding implied CONFIGs

Some CONFIG options can be implied by others and this can help to reduce the size of the defconfig files. For example, CONFIG_X86 implies CONFIG_CMD_IRQ, so we can put ‘imply CMD_IRQ’ under ‘config X86’ and all x86 boards will have that option, avoiding adding CONFIG_CMD_IRQ to each of the x86 defconfig files.

This tool can help find such configs. To use it, first build a database:

./tools/ -b

Then try to query it:

./tools/ -i CONFIG_I8042_KEYB
CONFIG_I8042_KEYB found in 33/5155 defconfigs
28 : CONFIG_X86
28 : CONFIG_I8259_PIC

This shows a list of config options which might imply CONFIG_I8042_KEYB along with how many defconfigs they cover. From this you can see that CONFIG_X86 generally implies CONFIG_I8042_KEYB but not always (28 out of 35). Therefore, instead of adding CONFIG_I8042_KEYB to the defconfig of every x86 board, you could add a single imply line to the Kconfig file:

config X86
    bool "x86 architecture"
    imply CMD_EEPROM

That will cover 28 defconfigs and you can perhaps find another condition that indicates that CONFIG_I8042_KEYB is not needed for the remaining 5 boards. Many of the options listed are not suitable as they are not related. E.g. it would be odd for CONFIG_RAMBASE to imply CONFIG_I8042_KEYB.

Using this search you can reduce the size of moveconfig patches.

You can automatically add ‘imply’ statements in the Kconfig with the -a option:

./tools/ -s -i CONFIG_SCSI \

This will add ‘imply SCSI’ to the two CONFIG options mentioned, assuming that the database indicates that they do actually imply CONFIG_SCSI and do not already have an ‘imply SCSI’.

The output shows where the imply is added:

18 : CONFIG_ARCH_LS1021A       arch/arm/cpu/armv7/ls102xa/Kconfig:1
13 : CONFIG_ARCH_LS1043A       arch/arm/cpu/armv8/fsl-layerscape/Kconfig:11
12 : CONFIG_ARCH_LS1046A       arch/arm/cpu/armv8/fsl-layerscape/Kconfig:31

The first number is the number of boards which can avoid having a special CONFIG_SCSI option in their defconfig file if this ‘imply’ is added. The location at the right is the Kconfig file and line number where the config appears. For example, adding ‘imply CONFIG_SCSI’ to the ‘config ARCH_LS1021A’ in arch/arm/cpu/armv7/ls102xa/Kconfig at line 1 will help 18 boards to reduce the size of their defconfig files.

If you want to add an ‘imply’ to every imply config in the list, you can use:

./tools/ -s -i CONFIG_SCSI -a all

To control which ones are displayed, use -I <list> where list is a list of options (use ‘-I help’ to see possible options and their meaning).

To skip showing you options that already have an ‘imply’ attached, use -A.

When you have finished adding ‘imply’ options you can regenerate the defconfig files for affected boards with something like:

git show --stat | ./tools/ -s -d -

This will regenerate only those defconfigs changed in the current commit. If you start with (say) 100 defconfigs being changed in the commit, and add a few ‘imply’ options as above, then regenerate, hopefully you can reduce the number of defconfigs changed in the commit.

Available options

-c, --color

Surround each portion of the log with escape sequences to display it in color on the terminal.

-C, --commit

Create a git commit with the changes when the operation is complete. A standard commit message is used which may need to be edited.

-d, --defconfigs

Specify a file containing a list of defconfigs to move. The defconfig files can be given with shell-style wildcards. Use ‘-‘ to read from stdin.

-f, --find

Find boards with a given config combination

-n, --dry-run

Perform a trial run that does not make any changes. It is useful to see what is going to happen before one actually runs it.

-e, --exit-on-error

Exit immediately if Make exits with a non-zero status while processing a defconfig file.

-s, --force-sync

Do “make savedefconfig” forcibly for all the defconfig files. If not specified, “make savedefconfig” only occurs for cases where at least one CONFIG was moved.

-S, --spl

Look for moved config options in spl/include/ instead of include/ This is useful for moving options for SPL build because SPL related options (mostly prefixed with CONFIG_SPL_) are sometimes blocked by CONFIG_SPL_BUILD ifdef conditionals.

-H, --headers-only

Only cleanup the headers; skip the defconfig processing

-j, --jobs

Specify the number of threads to run simultaneously. If not specified, the number of threads is the same as the number of CPU cores.

-r, --git-ref

Specify the git ref to clone for building the If unspecified use the CWD. This is useful for when changes to the Kconfig affect the default values and you want to capture the state of the defconfig from before that change was in effect. If in doubt, specify a ref pre-Kconfig changes (use HEAD if Kconfig changes are not committed). Worst case it will take a bit longer to run, but will always do the right thing.

-v, --verbose

Show any build errors as boards are built

-y, --yes

Instead of prompting, automatically go ahead with all operations. This includes cleaning up headers, the config whitelist and the README.

To see the complete list of supported options, run:

tools/ -h