dtsformat

A Small DTS/DTSI Formatter for Linux and Zephyr Device Trees

dtsformat is a small C formatter for Device Tree source files. It formats .dts and .dtsi files with a DTS-aware token/layout engine, reads project style from .dtsformat, and is intended to work well with both Linux-style DTS sources and Zephyr-style preprocessed DTS files.

The formatter supports:

• project-local configuration discovery through .dtsformat
• spaces or tabs for indentation
• configurable indentation width
• a configurable column limit used for line wrapping
• DTS includes via /include/ "file.dtsi"
• preprocessor lines such as #include, #ifdef, and #endif
• comments inside properties, including array/list values
• preservation of at most one empty line from the input

Key Features

• Formatter in C: A single native executable built with Meson.
• Project Config Discovery: Searches upward for .dtsformat next to the formatted file, similar to how .clang-format is typically used.
• Linux + Zephyr Coverage: Handles common Linux DTS style as well as Zephyr files that use C preprocessor directives.
• Configurable Indentation: Supports tabs or spaces with configurable width.
• Column-Aware Wrapping: Tries to wrap long property values and collections around a configured limit.
• Comment Preservation: Keeps line comments and block comments as explicit formatted lines, including comments embedded in array-style property values.
• Fixture Tests: Includes regression fixtures for includes, preprocessor directives, blank lines, and array comments.

Quickstart

1) Build the project

meson setup build
meson compile -C build

If ccache is configured in your environment and causes sandbox or temp-directory issues, this also works:

env CCACHE_DISABLE=1 meson compile -C build

2) Format a file

./build/dtsformat board.dts

3) Format a file in place

./build/dtsformat --in-place board.dts

4) Format from stdin

cat board.dts | ./build/dtsformat

Configuration Overview

The formatter looks for a .dtsformat file starting from the input file directory and walking upward. You can also provide a config explicitly with --config.

Example:

UseTab: Never
IndentWidth: 4
ColumnLimit: 88

Supported keys:

• UseTab: Always or Never
• IndentWidth: positive integer
• ColumnLimit: positive integer

Tool

dtsformat

Formats one or more DTS/DTSI files.

./build/dtsformat [--in-place] [--config PATH] [FILE ...]

Examples:

./build/dtsformat app.overlay
./build/dtsformat --in-place boards/my_board.dts
./build/dtsformat --config ./style/.dtsformat soc.dtsi

If no file is provided, dtsformat reads from stdin and writes formatted output to stdout.

Formatting Overview

The formatter currently aims to normalize:

• spacing around =, :, ,, and |
• indentation for nested nodes and property continuations
• wrapping of long <...> and [...] property values
• placement of standalone comments
• separation of preprocessor lines and /include/ directives
• preservation of one empty line between logical sections

Example:

#include "pinctrl.dtsi"

/ {
    zephyr,user {
        map =
            // Left
            <0>, <1>, <2>, <3>,
            // Right
            <4>, <5>, <6>, <7>;
    };
};

Documentation

Project documentation lives in the repository:

• Formatter Guide: docs/FORMATTER.md

Testing

Run the full suite with:

meson test -C build --print-errorlogs

The current tests cover:

• Linux-style DTS formatting
• Zephyr-style tab-indented formatting
• /include/ directives
• preprocessor directives such as #include and #ifdef
• blank-line preservation
• comments embedded in array/list property values

Building From Source

Requirements:

• Meson
• Ninja
• a C11 compiler
• Python 3 for the test runner

Typical build flow:

meson setup build
env CCACHE_DISABLE=1 meson compile -C build
env CCACHE_DISABLE=1 meson test -C build --print-errorlogs

Contributing

Useful reports and patches include:

• DTS formatting regressions
• Zephyr preprocessing edge cases
• Linux DTS style edge cases
• better wrapping heuristics for long property values
• additional regression fixtures
• documentation fixes

If you report an issue, include:

• the DTS/DTSI input
• the .dtsformat file, if any
• the command you ran
• the actual output
• the expected output