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101 lines
2.7 KiB
101 lines
2.7 KiB
2 years ago
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# Device Tree Compiler and libfdt
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The source tree contains the Device Tree Compiler (dtc) toolchain for
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working with device tree source and binary files and also libfdt, a
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utility library for reading and manipulating the binary format.
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dtc and libfdt are maintained by:
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* [David Gibson `<david@gibson.dropbear.id.au>`](mailto:david@gibson.dropbear.id.au)
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## Python library
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A Python library wrapping libfdt is also available. To build this you
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will need to install `swig` and Python development files. On Debian
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distributions:
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```
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$ sudo apt-get install swig python3-dev
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```
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The library provides an `Fdt` class which you can use like this:
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```
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$ PYTHONPATH=../pylibfdt python3
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>>> import libfdt
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>>> fdt = libfdt.Fdt(open('test_tree1.dtb', mode='rb').read())
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>>> node = fdt.path_offset('/subnode@1')
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>>> print(node)
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124
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>>> prop_offset = fdt.first_property_offset(node)
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>>> prop = fdt.get_property_by_offset(prop_offset)
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>>> print('%s=%s' % (prop.name, prop.as_str()))
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compatible=subnode1
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>>> node2 = fdt.path_offset('/')
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>>> print(fdt.getprop(node2, 'compatible').as_str())
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test_tree1
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```
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You will find tests in `tests/pylibfdt_tests.py` showing how to use each
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method. Help is available using the Python help command, e.g.:
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```
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$ cd pylibfdt
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$ python3 -c "import libfdt; help(libfdt)"
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```
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If you add new features, please check code coverage:
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```
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$ sudo apt-get install python3-coverage
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$ cd tests
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# It's just 'coverage' on most other distributions
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$ python3-coverage run pylibfdt_tests.py
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$ python3-coverage html
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# Open 'htmlcov/index.html' in your browser
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```
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The library can be installed with pip from a local source tree:
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```
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$ pip install . [--user|--prefix=/path/to/install_dir]
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```
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Or directly from a remote git repo:
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```
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$ pip install git+git://git.kernel.org/pub/scm/utils/dtc/dtc.git@main
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```
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The install depends on libfdt shared library being installed on the
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host system first. Generally, using `--user` or `--prefix` is not
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necessary and pip will use the default location for the Python
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installation which varies if the user is root or not.
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You can also install everything via make if you like, but pip is
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recommended.
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To install both libfdt and pylibfdt you can use:
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```
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$ make install [PREFIX=/path/to/install_dir]
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```
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To disable building the python library, even if swig and Python are available,
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use:
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```
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$ make NO_PYTHON=1
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```
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More work remains to support all of libfdt, including access to numeric
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values.
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## Mailing lists
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* The [devicetree-compiler](mailto:devicetree-compiler@vger.kernel.org)
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list is for discussion about dtc and libfdt implementation.
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* Core device tree bindings are discussed on the
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[devicetree-spec](mailto:devicetree-spec@vger.kernel.org) list.
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