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+#!/usr/bin/python
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+#
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+# Copyright (C) 2016 Google, Inc
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+# Written by Simon Glass <sjg@chromium.org>
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+#
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+# SPDX-License-Identifier: GPL-2.0+
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+#
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+
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+import command
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+import fdt_util
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+import sys
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+
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+# This deals with a device tree, presenting it as a list of Node and Prop
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+# objects, representing nodes and properties, respectively.
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+#
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+# This implementation uses the fdtget tool to access the device tree, so it
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+# is not very efficient for larger trees. The tool is called once for each
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+# node and property in the tree.
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+
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+class Prop:
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+ """A device tree property
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+
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+ Properties:
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+ name: Property name (as per the device tree)
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+ value: Property value as a string of bytes, or a list of strings of
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+ bytes
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+ type: Value type
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+ """
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+ def __init__(self, name, byte_list_str):
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+ self.name = name
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+ self.value = None
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+ if not byte_list_str.strip():
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+ self.type = fdt_util.TYPE_BOOL
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+ return
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+ bytes = [chr(int(byte, 16)) for byte in byte_list_str.strip().split(' ')]
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+ self.type, self.value = fdt_util.BytesToValue(''.join(bytes))
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+
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+ def GetPhandle(self):
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+ """Get a (single) phandle value from a property
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+
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+ Gets the phandle valuie from a property and returns it as an integer
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+ """
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+ return fdt_util.fdt32_to_cpu(self.value[:4])
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+
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+ def Widen(self, newprop):
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+ """Figure out which property type is more general
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+
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+ Given a current property and a new property, this function returns the
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+ one that is less specific as to type. The less specific property will
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+ be ble to represent the data in the more specific property. This is
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+ used for things like:
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+
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+ node1 {
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+ compatible = "fred";
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+ value = <1>;
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+ };
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+ node1 {
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+ compatible = "fred";
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+ value = <1 2>;
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+ };
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+
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+ He we want to use an int array for 'value'. The first property
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+ suggests that a single int is enough, but the second one shows that
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+ it is not. Calling this function with these two propertes would
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+ update the current property to be like the second, since it is less
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+ specific.
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+ """
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+ if newprop.type < self.type:
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+ self.type = newprop.type
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+
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+ if type(newprop.value) == list and type(self.value) != list:
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+ self.value = newprop.value
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+
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+class Node:
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+ """A device tree node
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+
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+ Properties:
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+ name: Device tree node tname
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+ path: Full path to node, along with the node name itself
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+ _fdt: Device tree object
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+ subnodes: A list of subnodes for this node, each a Node object
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+ props: A dict of properties for this node, each a Prop object.
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+ Keyed by property name
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+ """
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+ def __init__(self, fdt, name, path):
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+ self.name = name
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+ self.path = path
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+ self._fdt = fdt
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+ self.subnodes = []
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+ self.props = {}
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+
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+ def Scan(self):
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+ """Scan a node's properties and subnodes
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+
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+ This fills in the props and subnodes properties, recursively
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+ searching into subnodes so that the entire tree is built.
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+ """
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+ for name, byte_list_str in self._fdt.GetProps(self.path).iteritems():
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+ prop = Prop(name, byte_list_str)
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+ self.props[name] = prop
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+
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+ for name in self._fdt.GetSubNodes(self.path):
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+ sep = '' if self.path[-1] == '/' else '/'
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+ path = self.path + sep + name
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+ node = Node(self._fdt, name, path)
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+ self.subnodes.append(node)
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+
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+ node.Scan()
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+
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+
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+class Fdt:
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+ """Provides simple access to a flat device tree blob.
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+
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+ Properties:
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+ fname: Filename of fdt
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+ _root: Root of device tree (a Node object)
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+ """
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+
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+ def __init__(self, fname):
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+ self.fname = fname
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+
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+ def Scan(self):
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+ """Scan a device tree, building up a tree of Node objects
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+
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+ This fills in the self._root property
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+ """
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+ self._root = Node(self, '/', '/')
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+ self._root.Scan()
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+
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+ def GetRoot(self):
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+ """Get the root Node of the device tree
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+
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+ Returns:
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+ The root Node object
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+ """
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+ return self._root
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+
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+ def GetSubNodes(self, node):
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+ """Returns a list of sub-nodes of a given node
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+
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+ Args:
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+ node: Node name to return children from
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+
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+ Returns:
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+ List of children in the node (each a string node name)
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+
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+ Raises:
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+ CmdError: if the node does not exist.
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+ """
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+ out = command.Output('fdtget', self.fname, '-l', node)
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+ return out.strip().splitlines()
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+
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+ def GetProps(self, node, convert_dashes=False):
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+ """Get all properties from a node
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+
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+ Args:
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+ node: full path to node name to look in
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+ convert_dashes: True to convert - to _ in node names
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+
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+ Returns:
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+ A dictionary containing all the properties, indexed by node name.
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+ The entries are simply strings - no decoding of lists or numbers
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+ is done.
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+
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+ Raises:
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+ CmdError: if the node does not exist.
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+ """
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+ out = command.Output('fdtget', self.fname, node, '-p')
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+ props = out.strip().splitlines()
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+ props_dict = {}
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+ for prop in props:
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+ name = prop
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+ if convert_dashes:
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+ prop = re.sub('-', '_', prop)
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+ props_dict[prop] = self.GetProp(node, name)
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+ return props_dict
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+
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+ def GetProp(self, node, prop, default=None, typespec=None):
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+ """Get a property from a device tree.
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+
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+ This looks up the given node and property, and returns the value as a
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+ string,
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+
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+ If the node or property does not exist, this will return the default
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+ value.
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+
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+ Args:
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+ node: Full path to node to look up.
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+ prop: Property name to look up.
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+ default: Default value to return if nothing is present in the fdt,
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+ or None to raise in this case. This will be converted to a
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+ string.
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+ typespec: Type character to use (None for default, 's' for string)
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+
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+ Returns:
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+ string containing the property value.
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+
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+ Raises:
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+ CmdError: if the property does not exist and no default is provided.
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+ """
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+ args = [self.fname, node, prop, '-t', 'bx']
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+ if default is not None:
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+ args += ['-d', str(default)]
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+ if typespec is not None:
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+ args += ['-t%s' % typespec]
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+ out = command.Output('fdtget', *args)
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+ return out.strip()
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