README: Use meson in the Python section The Python section of README.md assumes a make build. It installs with 'make install', disables the library with NO_PYTHON, and runs its examples from the source tree, where make puts the built module. With meson the module is in the build directory instead, so the help example quietly imports whatever libfdt is installed, and the coverage example fails. Use meson to install and to disable the Python library, and run the examples from the build directory. Assisted-by: Claude:claude-opus-5-5 Signed-off-by: Simon Glass <sjg@chromium.org> Reviewed-by: David Gibson <david@gibson.dropbear.id.au> Reviewed-by: Herve Codina <herve.codina@bootlin.com> Message-ID: <20261028112007.3980089-2-sjg@chromium.org>
The source tree contains the Device Tree Compiler (dtc) toolchain for working with device tree source and binary files and also libfdt, a utility library for reading and manipulating the binary format.
dtc and libfdt are maintained by:
dtc and libfdt are built with Meson:
$ meson setup build $ meson compile -C build $ meson test -C build $ meson install -C build
meson configure build lists the build options, e.g. -Dpython=disabled to skip the Python library. See the Meson quick guide for more, such as installing with --destdir. scripts/install-deps.sh installs the packages needed on common systems.
Building with make still works but is deprecated.
A Python library wrapping libfdt is also available. To build this you will need to install swig and Python development files. On Debian distributions:
$ sudo apt-get install swig python3-dev
The library provides an Fdt class which you can use like this, from build/tests after running the tests:
$ PYTHONPATH=../pylibfdt python3
>>> import libfdt
>>> fdt = libfdt.Fdt(open('test_tree1.dtb', mode='rb').read())
>>> node = fdt.path_offset('/subnode@1')
>>> print(node)
124
>>> prop_offset = fdt.first_property_offset(node)
>>> prop = fdt.get_property_by_offset(prop_offset)
>>> print('%s=%s' % (prop.name, prop.as_str()))
compatible=subnode1
>>> node2 = fdt.path_offset('/')
>>> print(fdt.getprop(node2, 'compatible').as_str())
test_tree1
You will find tests in tests/pylibfdt_tests.py showing how to use each method. Help is available using the Python help command, e.g.:
$ cd build/pylibfdt $ python3 -c "import libfdt; help(libfdt)"
If you add new features, please check code coverage:
$ sudo apt-get install python3-coverage $ cd build/tests # It's just 'coverage' on most other distributions $ python3-coverage run ../../tests/pylibfdt_tests.py $ python3-coverage html # Open 'htmlcov/index.html' in your browser
The library can be installed with pip from a local source tree:
$ pip install . [--user|--prefix=/path/to/install_dir]
Or directly from a remote git repo:
$ pip install git+git://git.kernel.org/pub/scm/utils/dtc/dtc.git@main
The install depends on libfdt shared library being installed on the host system first. Generally, using --user or --prefix is not necessary and pip will use the default location for the Python installation which varies if the user is root or not.
You can also install everything with meson if you like, but pip is recommended.
To install both libfdt and pylibfdt you can use:
$ meson setup [--prefix=/path/to/install_dir] build $ meson install -C build
To disable building the python library, even if swig and Python are available, use:
$ meson setup -Dpython=disabled build
More work remains to support all of libfdt, including access to numeric values.