3 # Copyright (C) 2016 Google, Inc
4 # Written by Simon Glass <sjg@chromium.org>
6 # SPDX-License-Identifier: GPL-2.0+
13 from fdt import Fdt, NodeBase, PropBase
17 # This deals with a device tree, presenting it as a list of Node and Prop
18 # objects, representing nodes and properties, respectively.
20 # This implementation uses a libfdt Python library to access the device tree,
21 # so it is fairly efficient.
24 """A device tree property
27 name: Property name (as per the device tree)
28 value: Property value as a string of bytes, or a list of strings of
32 def __init__(self, node, offset, name, bytes):
33 PropBase.__init__(self, node, offset, name)
36 self.type = fdt.TYPE_BOOL
39 self.type, self.value = self.BytesToValue(bytes)
45 offset: Integer offset in the device tree
46 name: Device tree node tname
47 path: Full path to node, along with the node name itself
48 _fdt: Device tree object
49 subnodes: A list of subnodes for this node, each a Node object
50 props: A dict of properties for this node, each a Prop object.
51 Keyed by property name
53 def __init__(self, fdt, offset, name, path):
54 NodeBase.__init__(self, fdt, offset, name, path)
57 """Returns the offset of a node, after checking the cache
59 This should be used instead of self._offset directly, to ensure that
60 the cache does not contain invalid offsets.
62 self._fdt.CheckCache()
66 """Scan a node's properties and subnodes
68 This fills in the props and subnodes properties, recursively
69 searching into subnodes so that the entire tree is built.
71 self.props = self._fdt.GetProps(self, self.path)
73 offset = libfdt.fdt_first_subnode(self._fdt.GetFdt(), self.Offset())
75 sep = '' if self.path[-1] == '/' else '/'
76 name = libfdt.Name(self._fdt.GetFdt(), offset)
77 path = self.path + sep + name
78 node = Node(self._fdt, offset, name, path)
79 self.subnodes.append(node)
82 offset = libfdt.fdt_next_subnode(self._fdt.GetFdt(), offset)
84 def Refresh(self, my_offset):
85 """Fix up the _offset for each node, recursively
87 Note: This does not take account of property offsets - these will not
90 if self._offset != my_offset:
91 #print '%s: %d -> %d\n' % (self.path, self._offset, my_offset)
92 self._offset = my_offset
93 offset = libfdt.fdt_first_subnode(self._fdt.GetFdt(), self._offset)
94 for subnode in self.subnodes:
95 subnode.Refresh(offset)
96 offset = libfdt.fdt_next_subnode(self._fdt.GetFdt(), offset)
99 """Provides simple access to a flat device tree blob using libfdt.
102 _fdt: Device tree contents (bytearray)
103 _cached_offsets: True if all the nodes have a valid _offset property,
104 False if something has changed to invalidate the offsets
106 def __init__(self, fname):
107 Fdt.__init__(self, fname)
108 self._cached_offsets = False
110 self._fname = fdt_util.EnsureCompiled(self._fname)
112 with open(self._fname) as fd:
113 self._fdt = bytearray(fd.read())
116 """Get the contents of the FDT
119 The FDT contents as a string of bytes
123 def GetProps(self, node, path):
124 """Get all properties from a node.
127 node: Full path to node name to look in.
130 A dictionary containing all the properties, indexed by node name.
131 The entries are Prop objects.
134 ValueError: if the node does not exist.
136 offset = libfdt.fdt_path_offset(self._fdt, path)
140 poffset = libfdt.fdt_first_property_offset(self._fdt, offset)
142 dprop, plen = libfdt.fdt_get_property_by_offset(self._fdt, poffset)
143 prop = Prop(node, poffset, libfdt.String(self._fdt, dprop.nameoff),
145 props_dict[prop.name] = prop
147 poffset = libfdt.fdt_next_property_offset(self._fdt, poffset)
150 def Invalidate(self):
151 """Mark our offset cache as invalid"""
152 self._cached_offsets = False
154 def CheckCache(self):
155 """Refresh the offset cache if needed"""
156 if self._cached_offsets:
159 self._cached_offsets = True
162 """Refresh the offset cache"""
163 self._root.Refresh(0)
166 def Node(self, fdt, offset, name, path):
169 This is used by Fdt.Scan() to create a new node using the correct
174 offset: Offset of node
176 path: Full path to node
178 node = Node(fdt, offset, name, path)