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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 fdt_util
import libfdt
import sys
# 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:
"""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, name, bytes):
self.name = name
self.value = None
if not bytes:
self.type = fdt_util.TYPE_BOOL
self.value = True
return
self.type, self.value = fdt_util.BytesToValue(bytes)
def GetPhandle(self):
"""Get a (single) phandle value from a property
Gets the phandle valuie from a property and returns it as an integer
"""
return fdt_util.fdt32_to_cpu(self.value[:4])
def Widen(self, newprop):
"""Figure out which property type is more general
Given a current property and a new property, this function returns the
one that is less specific as to type. The less specific property will
be ble to represent the data in the more specific property. This is
used for things like:
node1 {
compatible = "fred";
value = <1>;
};
node1 {
compatible = "fred";
value = <1 2>;
};
He we want to use an int array for 'value'. The first property
suggests that a single int is enough, but the second one shows that
it is not. Calling this function with these two propertes would
update the current property to be like the second, since it is less
specific.
"""
if newprop.type < self.type:
self.type = newprop.type
if type(newprop.value) == list and type(self.value) != list:
self.value = [self.value]
if type(self.value) == list and len(newprop.value) > len(self.value):
val = fdt_util.GetEmpty(self.type)
while len(self.value) < len(newprop.value):
self.value.append(val)
class Node:
"""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):
self.offset = offset
self.name = name
self.path = path
self._fdt = fdt
self.subnodes = []
self.props = {}
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 Fdt:
"""Provides simple access to a flat device tree blob.
Properties:
fname: Filename of fdt
_root: Root of device tree (a Node object)
"""
def __init__(self, fname):
self.fname = fname
with open(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 Scan(self):
"""Scan a device tree, building up a tree of Node objects
This fills in the self._root property
"""
self._root = Node(self, 0, '/', '/')
self._root.Scan()
def GetRoot(self):
"""Get the root Node of the device tree
Returns:
The root Node object
"""
return self._root
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(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
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