PX4-Autopilot/CONTRIBUTING.md

Contributing to PX4-Autopilot

We follow the GitHub flow development model.

Fork the project, then clone your repo

First fork and clone the project.

Create a feature branch

Always branch off main for new features.

git checkout -b mydescriptivebranchname

Edit and build the code

The developer guide explains how to set up the development environment on Mac OS, Linux or Windows.

Coding standards

All C/C++ code must follow the PX4 coding style. Formatting is enforced by astyle in CI (make check_format). Code quality checks run via clang-tidy. Pull requests that fail either check will not be merged.

Python code is checked with mypy and flake8.

Commit message convention

PX4 uses conventional commits for all commit messages and PR titles.

Format

type(scope): short description of the change

Part	Rule
type	Category of change (see types table below)
scope	The module, driver, board, or area of PX4 affected
! (optional)	Append before : to mark a breaking change
description	What the change does, at least 5 characters, written in imperative form

Types

Type	Description
feat	A new feature
fix	A bug fix
docs	Documentation only changes
style	Formatting, whitespace, no code change
refactor	Code change that neither fixes a bug nor adds a feature
perf	Performance improvement
test	Adding or correcting tests
build	Build system or external dependencies
ci	CI configuration files and scripts
chore	Other changes that don't modify src or test files
revert	Reverts a previous commit

Scopes

The scope identifies which part of PX4 is affected. Common scopes:

Scope	Area
ekf2	Extended Kalman Filter (state estimation)
mavlink	MAVLink messaging protocol
commander	Commander and mode management
navigator	Mission, RTL, Land, and other navigation modes
sensors	Sensor drivers and processing
drivers	Hardware drivers
boards/px4_fmu-v6x	Board-specific changes (use the board name)
mc_att_control	Multicopter attitude control
mc_pos_control	Multicopter position control
fw_att_control	Fixed-wing attitude control
vtol	VTOL-specific logic
actuators	Mixer and actuator output
battery	Battery monitoring and estimation
logger	On-board logging
param	Parameter system
simulation	SITL, Gazebo, SIH
ci	Continuous integration and workflows
docs	Documentation
build	CMake, toolchain, build system
uorb	Inter-module messaging

For changes spanning multiple subsystems, use the primary one affected. Look at the directory path of the files you changed to find the right scope: src/modules/ekf2/ uses ekf2, src/drivers/imu/ uses drivers/imu, .github/workflows/ uses ci.

Breaking changes

Append ! before the colon to indicate a breaking change:

feat(ekf2)!: remove deprecated height fusion API

Good commit messages

feat(ekf2): add height fusion timeout
fix(mavlink): correct BATTERY_STATUS_V2 parsing
refactor(navigator): simplify RTL altitude logic
ci(workflows): migrate to reusable workflows
docs(ekf2): update tuning guide
feat(boards/px4_fmu-v6x)!: remove deprecated driver API
perf(mc_rate_control): reduce loop latency

Commits to avoid

These will be flagged by CI and should be squashed or reworded before merging:

fix                                    # too vague, no type or scope
update                                 # too vague, no type or scope
ekf2: fix something                   # missing type prefix
apply suggestions from code review     # squash into parent commit
do make format                         # squash into parent commit
WIP: trying something                  # not ready for main
oops                                   # not descriptive

PR titles

The PR title follows the same type(scope): description format. This is enforced by CI and is especially important because the PR title becomes the commit message when a PR is squash-merged.

Merge policy

Commits should be atomic and independently revertable. Squash at reviewer discretion for obvious cases (multiple WIP commits, messy review-response history). When your commits are clean and logical, they will be preserved as individual commits on main.

Cleaning up commits

If CI flags your commit messages, you can fix them with an interactive rebase:

# Squash all commits into one:
git rebase -i HEAD~N   # replace N with the number of commits
# mark all commits except the first as 'squash' or 'fixup'
# reword the remaining commit to follow the format
git push --force-with-lease

# Or reword specific commits:
git rebase -i HEAD~N
# mark the bad commits as 'reword'
git push --force-with-lease

Test your changes

PX4 is safety-critical software. All contributions must include adequate testing where practical:

• New features must include unit tests and/or integration tests that exercise the new functionality, where practical. Hardware-dependent changes that cannot be tested in SITL should include bench test or flight test evidence.
• Bug fixes must include a regression test where practical. When automated testing is not feasible (hardware-specific issues, race conditions, etc.), provide a link to a flight log demonstrating the fix and the reproduction steps for the original bug.
• Reviewers will verify that tests or test evidence exist before approving a pull request.

Types of tests

Test type	When to use	How to run
Unit tests (gtest)	Module-level logic, math, parsing	make tests
SITL integration tests (MAVSDK)	Flight behavior, failsafes, missions	test/mavsdk_tests/
Bench tests / flight logs	Hardware-dependent changes	Upload logs to Flight Review

Since we care about safety, we will regularly ask you for test results. Best is to do a test flight (or bench test where it applies) and upload the log file from it (on the microSD card in the logs directory) to Google Drive or Dropbox and share the link.

Push your changes

Push changes to your repo and send a pull request.

Make sure to provide some testing feedback and if possible the link to a flight log file. Upload flight log files to Flight Review and link the resulting report.