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.
23 def CheckErr(errnum, msg):
25 raise ValueError('Error %d: %s: %s' %
26 (errnum, libfdt.fdt_strerror(errnum), msg))
29 """A device tree property
32 name: Property name (as per the device tree)
33 value: Property value as a string of bytes, or a list of strings of
37 def __init__(self, node, offset, name, bytes):
38 PropBase.__init__(self, node, offset, name)
41 self.type = fdt.TYPE_BOOL
44 self.type, self.value = self.BytesToValue(bytes)
50 offset: Integer offset in the device tree
51 name: Device tree node tname
52 path: Full path to node, along with the node name itself
53 _fdt: Device tree object
54 subnodes: A list of subnodes for this node, each a Node object
55 props: A dict of properties for this node, each a Prop object.
56 Keyed by property name
58 def __init__(self, fdt, offset, name, path):
59 NodeBase.__init__(self, fdt, offset, name, path)
62 """Returns the offset of a node, after checking the cache
64 This should be used instead of self._offset directly, to ensure that
65 the cache does not contain invalid offsets.
67 self._fdt.CheckCache()
71 """Scan a node's properties and subnodes
73 This fills in the props and subnodes properties, recursively
74 searching into subnodes so that the entire tree is built.
76 self.props = self._fdt.GetProps(self, self.path)
78 offset = libfdt.fdt_first_subnode(self._fdt.GetFdt(), self.Offset())
80 sep = '' if self.path[-1] == '/' else '/'
81 name = libfdt.Name(self._fdt.GetFdt(), offset)
82 path = self.path + sep + name
83 node = Node(self._fdt, offset, name, path)
84 self.subnodes.append(node)
87 offset = libfdt.fdt_next_subnode(self._fdt.GetFdt(), offset)
89 def Refresh(self, my_offset):
90 """Fix up the _offset for each node, recursively
92 Note: This does not take account of property offsets - these will not
95 if self._offset != my_offset:
96 #print '%s: %d -> %d\n' % (self.path, self._offset, my_offset)
97 self._offset = my_offset
98 offset = libfdt.fdt_first_subnode(self._fdt.GetFdt(), self._offset)
99 for subnode in self.subnodes:
100 subnode.Refresh(offset)
101 offset = libfdt.fdt_next_subnode(self._fdt.GetFdt(), offset)
103 def DeleteProp(self, prop_name):
104 """Delete a property of a node
106 The property is deleted and the offset cache is invalidated.
109 prop_name: Name of the property to delete
111 ValueError if the property does not exist
113 CheckErr(libfdt.fdt_delprop(self._fdt.GetFdt(), self.Offset(), prop_name),
114 "Node '%s': delete property: '%s'" % (self.path, prop_name))
115 del self.props[prop_name]
116 self._fdt.Invalidate()
118 class FdtNormal(Fdt):
119 """Provides simple access to a flat device tree blob using libfdt.
122 _fdt: Device tree contents (bytearray)
123 _cached_offsets: True if all the nodes have a valid _offset property,
124 False if something has changed to invalidate the offsets
126 def __init__(self, fname):
127 Fdt.__init__(self, fname)
128 self._cached_offsets = False
130 self._fname = fdt_util.EnsureCompiled(self._fname)
132 with open(self._fname) as fd:
133 self._fdt = bytearray(fd.read())
136 """Get the contents of the FDT
139 The FDT contents as a string of bytes
143 def GetProps(self, node, path):
144 """Get all properties from a node.
147 node: Full path to node name to look in.
150 A dictionary containing all the properties, indexed by node name.
151 The entries are Prop objects.
154 ValueError: if the node does not exist.
156 offset = libfdt.fdt_path_offset(self._fdt, path)
160 poffset = libfdt.fdt_first_property_offset(self._fdt, offset)
162 dprop, plen = libfdt.fdt_get_property_by_offset(self._fdt, poffset)
163 prop = Prop(node, poffset, libfdt.String(self._fdt, dprop.nameoff),
165 props_dict[prop.name] = prop
167 poffset = libfdt.fdt_next_property_offset(self._fdt, poffset)
170 def Invalidate(self):
171 """Mark our offset cache as invalid"""
172 self._cached_offsets = False
174 def CheckCache(self):
175 """Refresh the offset cache if needed"""
176 if self._cached_offsets:
179 self._cached_offsets = True
182 """Refresh the offset cache"""
183 self._root.Refresh(0)
186 def Node(self, fdt, offset, name, path):
189 This is used by Fdt.Scan() to create a new node using the correct
194 offset: Offset of node
196 path: Full path to node
198 node = Node(fdt, offset, name, path)