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There is a need to be able to specify some options when building an FDT with the SW interface. This can be accomplished with minimal changes by storing intermediate data in the fdt header itself, in fields that are not otherwise needed during the creation process and can be set by fdt_finish(). The fdt.magic field is already used exactly this way, as a state to check with callers that the FDT has been created but not yet finished. fdt.version and fdt.last_comp_version are used to make room for more intermediate state. These are adjacent and unused during the building process. last_comp_version is not yet used for intermediate state, but it is zeroed and treated as used, so as to allow future growth easily. A new interface, fdt_create_with_flags() is added, which takes 32-bit flag value to control creation. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Message-Id: <20190509094122.834-3-npiggin@gmail.com> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
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:
David Gibson <david@gibson.dropbear.id.au>
Jon Loeliger <jdl@jdl.com>
Python library
--------------
A Python library is also available. To build this you will need to install
swig and Python development files. On Debian distributions:
sudo apt-get install swig python-dev
The library provides an Fdt class which you can use like this:
$ PYTHONPATH=../pylibfdt python
>>> import libfdt
>>> fdt = libfdt.Fdt(open('test_tree1.dtb').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=%r' % (prop.name, prop.value)
compatible=bytearray(b'subnode1\x00')
>>> print '%s=%s' % (prop.name, prop.value)
compatible=subnode1
>>> node2 = fdt.path_offset('/')
>>> print fdt.getprop(node2, 'compatible')
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 pylibfdt
$ python -c "import libfdt; help(libfdt)"
If you add new features, please check code coverage:
$ sudo apt-get install python-pip python-pytest
$ sudo pip install coverage
$ cd tests
$ coverage run pylibfdt_tests.py
$ coverage html
# Open 'htmlcov/index.html' in your browser
To install the library via the normal setup.py method, use:
./pylibfdt/setup.py [--prefix=/path/to/install_dir]
If --prefix is not provided, the default prefix is used, typically '/usr'
or '/usr/local'. See Python's distutils documentation for details. You can
also install via the Makefile if you like, but the above is more common.
To install both libfdt and pylibfdt you can use:
make install [SETUP_PREFIX=/path/to/install_dir] \
[PREFIX=/path/to/install_dir]
To disable building the python library, even if swig and Python are available,
use:
make NO_PYTHON=1
More work remains to support all of libfdt, including access to numeric
values.
Tests
-----
Test files are kept in the tests/ directory. Use 'make check' to build and run
all tests.
If you want to adjust a test file, be aware that tree_tree1.dts is compiled
and checked against a binary tree from assembler macros in trees.S. So
if you change that file you must change tree.S also.
Mailing list
------------
The following list is for discussion about dtc and libfdt implementation
mailto:devicetree-compiler@vger.kernel.org
Core device tree bindings are discussed on the devicetree-spec list:
mailto:devicetree-spec@vger.kernel.org