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Add an initial Python library for libfdt

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Add Python bindings for a bare-bones set of libfdt functions. These allow
navigating the tree and reading node names and properties.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Simon Glass 2017-03-17 16:14:30 -06:00 committed by David Gibson
parent cdbb2b6c7a
commit 50f2507016
5 changed files with 488 additions and 0 deletions
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1
Makefile
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@ -22,6 +22,7 @@ CFLAGS = -g -Os -fPIC -Werror $(WARNINGS)
BISON = bison
LEX = flex
SWIG = swig
INSTALL = /usr/bin/install
DESTDIR =

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pylibfdt/.gitignore vendored Normal file
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libfdt.py
libfdt.pyc
libfdt_wrap.c

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pylibfdt/Makefile.pylibfdt Normal file
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# Makefile.pylibfdt
#
PYLIBFDT_srcs = $(addprefix $(LIBFDT_srcdir)/,$(LIBFDT_SRCS))
WRAP = $(PYLIBFDT_objdir)/libfdt_wrap.c
PYMODULE = $(PYLIBFDT_objdir)/_libfdt.so
$(PYMODULE): $(PYLIBFDT_srcs) $(WRAP)
@$(VECHO) PYMOD $@
python $(PYLIBFDT_objdir)/setup.py "$(CPPFLAGS)" $^
mv _libfdt.so $(PYMODULE)
$(WRAP): $(PYLIBFDT_srcdir)/libfdt.swig
@$(VECHO) SWIG $@
$(SWIG) -python -o $@ $<
PYLIBFDT_cleanfiles = libfdt_wrap.c libfdt.py libfdt.pyc _libfdt.so

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pylibfdt/libfdt.swig Normal file
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/*
* pylibfdt - Flat Device Tree manipulation in Python
* Copyright (C) 2017 Google, Inc.
* Written by Simon Glass <sjg@chromium.org>
*
* libfdt is dual licensed: you can use it either under the terms of
* the GPL, or the BSD license, at your option.
*
* a) This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this library; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
* MA 02110-1301 USA
*
* Alternatively,
*
* b) Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* 1. Redistributions of source code must retain the above
* copyright notice, this list of conditions and the following
* disclaimer.
* 2. Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials
* provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
%module libfdt
%{
#define SWIG_FILE_WITH_INIT
#include "libfdt.h"
%}
%pythoncode %{
import struct
# Error codes, corresponding to FDT_ERR_... in libfdt.h
(NOTFOUND,
EXISTS,
NOSPACE,
BADOFFSET,
BADPATH,
BADPHANDLE,
BADSTATE,
TRUNCATED,
BADMAGIC,
BADVERSION,
BADSTRUCTURE,
BADLAYOUT,
INTERNAL,
BADNCELLS,
BADVALUE,
BADOVERLAY,
NOPHANDLES) = QUIET_ALL = range(1, 18)
# QUIET_ALL can be passed as the 'quiet' parameter to avoid exceptions
# altogether. All # functions passed this value will return an error instead
# of raising an exception.
# Pass this as the 'quiet' parameter to return -ENOTFOUND on NOTFOUND errors,
# instead of raising an exception.
QUIET_NOTFOUND = (NOTFOUND,)
class FdtException(Exception):
"""An exception caused by an error such as one of the codes above"""
def __init__(self, err):
self.err = err
def __str__(self):
return 'pylibfdt error %d: %s' % (self.err, fdt_strerror(self.err))
def strerror(fdt_err):
"""Get the string for an error number
Args:
fdt_err: Error number (-ve)
Returns:
String containing the associated error
"""
return fdt_strerror(fdt_err)
def check_err(val, quiet=()):
"""Raise an error if the return value is -ve
This is used to check for errors returned by libfdt C functions.
Args:
val: Return value from a libfdt function
quiet: Errors to ignore (empty to raise on all errors)
Returns:
val if val >= 0
Raises
FdtException if val < 0
"""
if val < 0:
if -val not in quiet:
raise FdtException(val)
return val
def check_err_null(val, quiet=()):
"""Raise an error if the return value is NULL
This is used to check for a NULL return value from certain libfdt C
functions
Args:
val: Return value from a libfdt function
quiet: Errors to ignore (empty to raise on all errors)
Returns:
val if val is a list, None if not
Raises
FdtException if val indicates an error was reported and the error
is not in @quiet.
"""
# Normally a list is returned which contains the data and its length.
# If we get just an integer error code, it means the function failed.
if not isinstance(val, list):
if -val not in quiet:
raise FdtException(val)
return val
class Fdt:
"""Device tree class, supporting all operations
The Fdt object is created is created from a device tree binary file,
e.g. with something like:
fdt = Fdt(open("filename.dtb").read())
Operations can then be performed using the methods in this class. Each
method xxx(args...) corresponds to a libfdt function fdt_xxx(fdt, args...).
All methods raise an FdtException if an error occurs. To avoid this
behaviour a 'quiet' parameter is provided for some functions. This
defaults to empty, but you can pass a list of errors that you expect.
If one of these errors occurs, the function will return an error number
(e.g. -NOTFOUND).
"""
def __init__(self, data):
self._fdt = bytearray(data)
check_err(fdt_check_header(self._fdt));
def path_offset(self, path, quiet=()):
"""Get the offset for a given path
Args:
path: Path to the required node, e.g. '/node@3/subnode@1'
quiet: Errors to ignore (empty to raise on all errors)
Returns:
Node offset
Raises
FdtException if the path is not valid or not found
"""
return check_err(fdt_path_offset(self._fdt, path), quiet)
def first_property_offset(self, nodeoffset, quiet=()):
"""Get the offset of the first property in a node offset
Args:
nodeoffset: Offset to the node to check
quiet: Errors to ignore (empty to raise on all errors)
Returns:
Offset of the first property
Raises
FdtException if the associated node has no properties, or some
other error occurred
"""
return check_err(fdt_first_property_offset(self._fdt, nodeoffset),
quiet)
def next_property_offset(self, prop_offset, quiet=()):
"""Get the next property in a node
Args:
prop_offset: Offset of the previous property
quiet: Errors to ignore (empty to raise on all errors)
Returns:
Offset of the next property
Raises:
FdtException if the associated node has no more properties, or
some other error occurred
"""
return check_err(fdt_next_property_offset(self._fdt, prop_offset),
quiet)
def get_name(self, nodeoffset):
"""Get the name of a node
Args:
nodeoffset: Offset of node to check
Returns:
Node name
Raises:
FdtException on error (e.g. nodeoffset is invalid)
"""
return check_err_null(fdt_get_name(self._fdt, nodeoffset))[0]
def get_property_by_offset(self, prop_offset, quiet=()):
"""Obtains a property that can be examined
Args:
prop_offset: Offset of property (e.g. from first_property_offset())
quiet: Errors to ignore (empty to raise on all errors)
Returns:
Property object, or None if not found
Raises:
FdtException on error (e.g. invalid prop_offset or device
tree format)
"""
pdata = check_err_null(
fdt_get_property_by_offset(self._fdt, prop_offset), quiet)
if isinstance(pdata, (int)):
return pdata
return Property(pdata[0], pdata[1])
def first_subnode(self, nodeoffset, quiet=()):
"""Find the first subnode of a parent node
Args:
nodeoffset: Node offset of parent node
quiet: Errors to ignore (empty to raise on all errors)
Returns:
The offset of the first subnode, if any
Raises:
FdtException if no subnode found or other error occurs
"""
return check_err(fdt_first_subnode(self._fdt, nodeoffset), quiet)
def next_subnode(self, nodeoffset, quiet=()):
"""Find the next subnode
Args:
nodeoffset: Node offset of previous subnode
quiet: Errors to ignore (empty to raise on all errors)
Returns:
The offset of the next subnode, if any
Raises:
FdtException if no more subnode found or other error occurs
"""
return check_err(fdt_next_subnode(self._fdt, nodeoffset), quiet)
def totalsize(self):
"""Return the total size of the device tree
Returns:
Total tree size in bytes
"""
return check_err(fdt_totalsize(self._fdt))
def off_dt_struct(self):
"""Return the start of the device tree struct area
Returns:
Start offset of struct area
"""
return check_err(fdt_off_dt_struct(self._fdt))
def pack(self, quiet=()):
"""Pack the device tree to remove unused space
This adjusts the tree in place.
Args:
quiet: Errors to ignore (empty to raise on all errors)
Raises:
FdtException if any error occurs
"""
return check_err(fdt_pack(self._fdt), quiet)
def delprop(self, nodeoffset, prop_name):
"""Delete a property from a node
Args:
nodeoffset: Node offset containing property to delete
prop_name: Name of property to delete
Raises:
FdtError if the property does not exist, or another error occurs
"""
return check_err(fdt_delprop(self._fdt, nodeoffset, prop_name))
def getprop(self, nodeoffset, prop_name, quiet=()):
"""Get a property from a node
Args:
nodeoffset: Node offset containing property to get
prop_name: Name of property to get
quiet: Errors to ignore (empty to raise on all errors)
Returns:
Value of property as a bytearray, or -ve error number
Raises:
FdtError if any error occurs (e.g. the property is not found)
"""
pdata = check_err_null(fdt_getprop(self._fdt, nodeoffset, prop_name),
quiet)
if isinstance(pdata, (int)):
return pdata
return bytearray(pdata[0])
class Property:
"""Holds a device tree property name and value.
This holds a copy of a property taken from the device tree. It does not
reference the device tree, so if anything changes in the device tree,
a Property object will remain valid.
Properties:
name: Property name
value: Proper value as a bytearray
"""
def __init__(self, name, value):
self.name = name
self.value = value
%}
%rename(fdt_property) fdt_property_func;
typedef int fdt32_t;
%include "libfdt/fdt.h"
%include "typemaps.i"
/* Most functions don't change the device tree, so use a const void * */
%typemap(in) (const void *)(const void *fdt) {
if (!PyByteArray_Check($input)) {
SWIG_exception_fail(SWIG_TypeError, "in method '" "$symname"
"', argument " "$argnum"" of type '" "$type""'");
}
$1 = (void *)PyByteArray_AsString($input);
fdt = $1;
fdt = fdt; /* avoid unused variable warning */
}
/* Some functions do change the device tree, so use void * */
%typemap(in) (void *)(const void *fdt) {
if (!PyByteArray_Check($input)) {
SWIG_exception_fail(SWIG_TypeError, "in method '" "$symname"
"', argument " "$argnum"" of type '" "$type""'");
}
$1 = PyByteArray_AsString($input);
fdt = $1;
fdt = fdt; /* avoid unused variable warning */
}
%typemap(out) (struct fdt_property *) {
PyObject *buff;
if ($1) {
resultobj = PyString_FromString(
fdt_string(fdt1, fdt32_to_cpu($1->nameoff)));
buff = PyByteArray_FromStringAndSize(
(const char *)($1 + 1), fdt32_to_cpu($1->len));
resultobj = SWIG_Python_AppendOutput(resultobj, buff);
}
}
%apply int *OUTPUT { int *lenp };
/* typemap used for fdt_getprop() */
%typemap(out) (const void *) {
if (!$1)
$result = Py_None;
else
$result = Py_BuildValue("s#", $1, *arg4);
}
/* We have both struct fdt_property and a function fdt_property() */
%warnfilter(302) fdt_property;
/* These are macros in the header so have to be redefined here */
int fdt_magic(const void *fdt);
int fdt_totalsize(const void *fdt);
int fdt_off_dt_struct(const void *fdt);
int fdt_off_dt_strings(const void *fdt);
int fdt_off_mem_rsvmap(const void *fdt);
int fdt_version(const void *fdt);
int fdt_last_comp_version(const void *fdt);
int fdt_boot_cpuid_phys(const void *fdt);
int fdt_size_dt_strings(const void *fdt);
int fdt_size_dt_struct(const void *fdt);
%include <../libfdt/libfdt.h>

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#!/usr/bin/env python
"""
setup.py file for SWIG libfdt
"""
from distutils.core import setup, Extension
import os
import sys
progname = sys.argv[0]
cflags = sys.argv[1]
files = sys.argv[2:]
if cflags:
cflags = [flag for flag in cflags.split(' ') if flag]
else:
cflags = None
libfdt_module = Extension(
'_libfdt',
sources = files,
extra_compile_args = cflags
)
sys.argv = [progname, '--quiet', 'build_ext', '--inplace']
setup (name = 'libfdt',
version = '0.1',
author = "Simon Glass <sjg@chromium.org>",
description = """Python binding for libfdt""",
ext_modules = [libfdt_module],
py_modules = ["libfdt"],
)