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107 lines
3.2 KiB
Text
107 lines
3.2 KiB
Text
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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>
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Jon Loeliger <loeliger@gmail.com>
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Python library
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--------------
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A Python library is also available. To build this you will need to install
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swig and Python development files. On Debian distributions:
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sudo apt-get install swig python3-dev
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The library provides an Fdt class which you can use like this:
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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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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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$ cd pylibfdt
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$ python3 -c "import libfdt; help(libfdt)"
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If you add new features, please check code coverage:
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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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The library can be installed with pip from a local source tree:
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pip install . [--user|--prefix=/path/to/install_dir]
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Or directly from a remote git repo:
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pip install git+git://git.kernel.org/pub/scm/utils/dtc/dtc.git@main
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The install depends on libfdt shared library being installed on the host system
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first. Generally, using --user or --prefix is not necessary and pip will use the
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default location for the Python installation which varies if the user is root or
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not.
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You can also install everything via make if you like, but pip is recommended.
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To install both libfdt and pylibfdt you can use:
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make install [PREFIX=/path/to/install_dir]
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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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make NO_PYTHON=1
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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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Adding a new function to libfdt.h
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---------------------------------
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The shared library uses libfdt/version.lds to list the exported functions, so
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add your new function there. Check that your function works with pylibfdt. If
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it cannot be supported, put the declaration in libfdt.h behind #ifndef SWIG so
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that swig ignores it.
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Tests
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-----
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Test files are kept in the tests/ directory. Use 'make check' to build and run
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all tests.
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If you want to adjust a test file, be aware that tree_tree1.dts is compiled
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and checked against a binary tree from assembler macros in trees.S. So
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if you change that file you must change tree.S also.
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Mailing list
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------------
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The following list is for discussion about dtc and libfdt implementation
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mailto:devicetree-compiler@vger.kernel.org
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Core device tree bindings are discussed on the devicetree-spec list:
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mailto:devicetree-spec@vger.kernel.org
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