Coding Style Guidelines

Style Tools

Checkpatch

The Linux kernel GPL-licensed tool checkpatch is used to check coding style conformity.

Note

checkpatch does not currently run on Windows.

Checkpatch is available in the scripts directory. To invoke it when committing code, make the file $ZEPHYR_BASE/.git/hooks/pre-commit executable and edit it to contain:

#!/bin/sh
set -e exec
exec git diff --cached | ${ZEPHYR_BASE}/scripts/checkpatch.pl -

Instead of running checkpatch at each commit, you may prefer to run it only before pushing on zephyr repo. To do this, make the file $ZEPHYR_BASE/.git/hooks/pre-push executable and edit it to contain:

#!/bin/sh
remote="$1"
url="$2"

z40=0000000000000000000000000000000000000000

echo "Run push hook"

while read local_ref local_sha remote_ref remote_sha
do
    args="$remote $url $local_ref $local_sha $remote_ref $remote_sha"
    exec ${ZEPHYR_BASE}/scripts/series-push-hook.sh $args
done

exit 0

If you want to override checkpatch verdict and push you branch despite reported issues, you can add option –no-verify to the git push command.

Checkpatch reads default options from a .checkpatch.conf file, searched for in the current directory, $HOME and .scripts, in that order. The Zephyr tree provides one at its top level. To use a configuration file from another directory, for example when checking a repository outside the Zephyr tree, set the CHECKPATCH_CONFIG_DIR environment variable to the directory containing it:

CHECKPATCH_CONFIG_DIR=/path/to/config ${ZEPHYR_BASE}/scripts/checkpatch.pl -

If CHECKPATCH_CONFIG_DIR is set but contains no .checkpatch.conf, checkpatch prints a warning and falls back to the default search path. An empty value is ignored. Relative paths inside the configuration file, such as --typedefsfile, are still resolved against the current directory.

A different way for running checkpatch is by using check_compliance.py script, which does additional style and compliance related checks.

clang-format

The clang-format tool can be helpful to quickly reformat large amounts of new source code to our Coding Style Guidelines standards together with the .clang-format configuration file provided in the repository. clang-format is well integrated into most editors, but you can also run it manually like this:

clang-format -i my_source_file.c

clang-format is part of LLVM, which can be downloaded from the project releases page. Note that if you are a Linux user, clang-format will likely be available as a package in your distribution repositories.

When there are differences between the Coding Style Guidelines guidelines and the formatting generated by code formatting tools, the Coding Style Guidelines guidelines take precedence. If there is ambiguity between formatting tools and the guidelines, maintainers may decide which style should be adopted.

dts-linter

The dts-linter can be helpful to quickly reformat large amounts of devicetree files to our Coding Style Guidelines standards. You can also run it manually like this:

For individual files

npx --ignore-scripts --prefix ./scripts/ci dts-linter --format --file board.dts --file board_pinctrl.dtsi --patchFile diff.patch --enableSortNodesAndProperties --sortNodesNodesBy address
git apply diff.patch

You can omit --file and this will format all files under the directory where the command has been called. Alternatively --cwd can also be passed set the base dir where the tool should look for files. This option is also used to make the paths relative in the patch file.

You can also fix in place with

npx --ignore-scripts --prefix ./scripts/ci dts-linter --formatFixAll --enableSortNodesAndProperties --sortNodesNodesBy address

Editor Integration

Make sure you follow Devicetree Style Guidelines requirements to configure the editor correctly.