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#!/usr/bin/python
#
# Copyright (C) 2016 Google, Inc
# Written by Simon Glass <sjg@chromium.org>
#
# SPDX-License-Identifier: GPL-2.0+
#
import struct
import sys
import fdt
from fdt import Fdt, NodeBase, PropBase
import fdt_util
import libfdt
# This deals with a device tree, presenting it as a list of Node and Prop
# objects, representing nodes and properties, respectively.
#
# This implementation uses a libfdt Python library to access the device tree,
# so it is fairly efficient.
class Prop(PropBase):
"""A device tree property
Properties:
name: Property name (as per the device tree)
value: Property value as a string of bytes, or a list of strings of
bytes
type: Value type
"""
def __init__(self, node, offset, name, bytes):
PropBase.__init__(self, node, offset, name)
self.bytes = bytes
if not bytes:
self.type = fdt.TYPE_BOOL
self.value = True
return
self.type, self.value = self.BytesToValue(bytes)
class Node(NodeBase):
"""A device tree node
Properties:
offset: Integer offset in the device tree
name: Device tree node tname
path: Full path to node, along with the node name itself
_fdt: Device tree object
subnodes: A list of subnodes for this node, each a Node object
props: A dict of properties for this node, each a Prop object.
Keyed by property name
"""
def __init__(self, fdt, offset, name, path):
NodeBase.__init__(self, fdt, offset, name, path)
def Scan(self):
"""Scan a node's properties and subnodes
This fills in the props and subnodes properties, recursively
searching into subnodes so that the entire tree is built.
"""
self.props = self._fdt.GetProps(self.path)
offset = libfdt.fdt_first_subnode(self._fdt.GetFdt(), self._offset)
while offset >= 0:
sep = '' if self.path[-1] == '/' else '/'
name = libfdt.Name(self._fdt.GetFdt(), offset)
path = self.path + sep + name
node = Node(self._fdt, offset, name, path)
self.subnodes.append(node)
node.Scan()
offset = libfdt.fdt_next_subnode(self._fdt.GetFdt(), offset)
class FdtNormal(Fdt):
"""Provides simple access to a flat device tree blob using libfdt.
Properties:
_fdt: Device tree contents (bytearray)
_cached_offsets: True if all the nodes have a valid _offset property,
False if something has changed to invalidate the offsets
"""
def __init__(self, fname):
Fdt.__init__(self, fname)
if self._fname:
self._fname = fdt_util.EnsureCompiled(self._fname)
with open(self._fname) as fd:
self._fdt = fd.read()
def GetFdt(self):
"""Get the contents of the FDT
Returns:
The FDT contents as a string of bytes
"""
return self._fdt
def GetProps(self, node):
"""Get all properties from a node.
Args:
node: Full path to node name to look in.
Returns:
A dictionary containing all the properties, indexed by node name.
The entries are Prop objects.
Raises:
ValueError: if the node does not exist.
"""
offset = libfdt.fdt_path_offset(self._fdt, node)
if offset < 0:
libfdt.Raise(offset)
props_dict = {}
poffset = libfdt.fdt_first_property_offset(self._fdt, offset)
while poffset >= 0:
dprop, plen = libfdt.fdt_get_property_by_offset(self._fdt, poffset)
prop = Prop(node, poffset, libfdt.String(self._fdt, dprop.nameoff),
libfdt.Data(dprop))
props_dict[prop.name] = prop
poffset = libfdt.fdt_next_property_offset(self._fdt, poffset)
return props_dict
@classmethod
def Node(self, fdt, offset, name, path):
"""Create a new node
This is used by Fdt.Scan() to create a new node using the correct
class.
Args:
fdt: Fdt object
offset: Offset of node
name: Node name
path: Full path to node
"""
node = Node(fdt, offset, name, path)
return node
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