3 # Copyright (C) 2016 Google, Inc
4 # Written by Simon Glass <sjg@chromium.org>
6 # SPDX-License-Identifier: GPL-2.0+
11 from fdt import Fdt, NodeBase, PropBase
15 # This deals with a device tree, presenting it as a list of Node and Prop
16 # objects, representing nodes and properties, respectively.
18 # This implementation uses the fdtget tool to access the device tree, so it
19 # is not very efficient for larger trees. The tool is called once for each
20 # node and property in the tree.
23 """A device tree property
26 name: Property name (as per the device tree)
27 value: Property value as a string of bytes, or a list of strings of
31 def __init__(self, node, name, byte_list_str):
32 PropBase.__init__(self, node, 0, name)
33 if not byte_list_str.strip():
34 self.type = fdt.TYPE_BOOL
36 self.bytes = [chr(int(byte, 16))
37 for byte in byte_list_str.strip().split(' ')]
38 self.type, self.value = self.BytesToValue(''.join(self.bytes))
45 name: Device tree node tname
46 path: Full path to node, along with the node name itself
47 _fdt: Device tree object
48 subnodes: A list of subnodes for this node, each a Node object
49 props: A dict of properties for this node, each a Prop object.
50 Keyed by property name
52 def __init__(self, fdt, offset, name, path):
53 NodeBase.__init__(self, fdt, offset, name, path)
56 """Scan a node's properties and subnodes
58 This fills in the props and subnodes properties, recursively
59 searching into subnodes so that the entire tree is built.
61 for name, byte_list_str in self._fdt.GetProps(self.path).iteritems():
62 prop = Prop(self, name, byte_list_str)
63 self.props[name] = prop
65 for name in self._fdt.GetSubNodes(self.path):
66 sep = '' if self.path[-1] == '/' else '/'
67 path = self.path + sep + name
68 node = Node(self._fdt, 0, name, path)
69 self.subnodes.append(node)
74 class FdtFallback(Fdt):
75 """Provides simple access to a flat device tree blob using fdtget/fdtput
81 def __init__(self, fname):
82 Fdt.__init__(self, fname)
84 self._fname = fdt_util.EnsureCompiled(self._fname)
86 def GetSubNodes(self, node):
87 """Returns a list of sub-nodes of a given node
90 node: Node name to return children from
93 List of children in the node (each a string node name)
96 CmdError: if the node does not exist.
98 out = command.Output('fdtget', self._fname, '-l', node)
99 return out.strip().splitlines()
101 def GetProps(self, node):
102 """Get all properties from a node
105 node: full path to node name to look in
108 A dictionary containing all the properties, indexed by node name.
109 The entries are simply strings - no decoding of lists or numbers
113 CmdError: if the node does not exist.
115 out = command.Output('fdtget', self._fname, node, '-p')
116 props = out.strip().splitlines()
120 props_dict[prop] = self.GetProp(node, name)
123 def GetProp(self, node, prop, default=None, typespec=None):
124 """Get a property from a device tree.
126 This looks up the given node and property, and returns the value as a
129 If the node or property does not exist, this will return the default
133 node: Full path to node to look up.
134 prop: Property name to look up.
135 default: Default value to return if nothing is present in the fdt,
136 or None to raise in this case. This will be converted to a
138 typespec: Type character to use (None for default, 's' for string)
141 string containing the property value.
144 CmdError: if the property does not exist and no default is provided.
146 args = [self._fname, node, prop, '-t', 'bx']
147 if default is not None:
148 args += ['-d', str(default)]
149 if typespec is not None:
150 args += ['-t%s' % typespec]
151 out = command.Output('fdtget', *args)
155 def Node(self, fdt, offset, name, path):
158 This is used by Fdt.Scan() to create a new node using the correct
163 offset: Offset of node
165 path: Full path to node
167 node = Node(fdt, offset, name, path)