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@@ -6,17 +6,26 @@
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# SPDX-License-Identifier: GPL-2.0+
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#
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-import fdt_util
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-import libfdt
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+import struct
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import sys
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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 a libfdt Python library to access the device tree,
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-# so it is fairly efficient.
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+import fdt_util
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+
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+# This deals with a device tree, presenting it as an assortment of Node and
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+# Prop objects, representing nodes and properties, respectively. This file
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+# contains the base classes and defines the high-level API. Most of the
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+# implementation is in the FdtFallback and FdtNormal subclasses. See
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+# fdt_select.py for how to create an Fdt object.
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+
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+# A list of types we support
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+(TYPE_BYTE, TYPE_INT, TYPE_STRING, TYPE_BOOL) = range(4)
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-class Prop:
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+def CheckErr(errnum, msg):
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+ if errnum:
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+ raise ValueError('Error %d: %s: %s' %
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+ (errnum, libfdt.fdt_strerror(errnum), msg))
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+
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+class PropBase:
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"""A device tree property
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Properties:
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@@ -25,14 +34,11 @@ class Prop:
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bytes
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type: Value type
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"""
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- def __init__(self, name, bytes):
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+ def __init__(self, node, offset, name):
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+ self._node = node
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+ self._offset = offset
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self.name = name
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self.value = None
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- if not bytes:
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- self.type = fdt_util.TYPE_BOOL
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- self.value = True
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- return
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- self.type, self.value = fdt_util.BytesToValue(bytes)
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def GetPhandle(self):
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"""Get a (single) phandle value from a property
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@@ -71,12 +77,85 @@ class Prop:
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self.value = [self.value]
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if type(self.value) == list and len(newprop.value) > len(self.value):
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- val = fdt_util.GetEmpty(self.type)
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+ val = self.GetEmpty(self.type)
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while len(self.value) < len(newprop.value):
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self.value.append(val)
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+ def BytesToValue(self, bytes):
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+ """Converts a string of bytes into a type and value
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+
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+ Args:
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+ A string containing bytes
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+
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+ Return:
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+ A tuple:
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+ Type of data
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+ Data, either a single element or a list of elements. Each element
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+ is one of:
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+ TYPE_STRING: string value from the property
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+ TYPE_INT: a byte-swapped integer stored as a 4-byte string
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+ TYPE_BYTE: a byte stored as a single-byte string
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+ """
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+ size = len(bytes)
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+ strings = bytes.split('\0')
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+ is_string = True
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+ count = len(strings) - 1
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+ if count > 0 and not strings[-1]:
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+ for string in strings[:-1]:
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+ if not string:
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+ is_string = False
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+ break
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+ for ch in string:
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+ if ch < ' ' or ch > '~':
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+ is_string = False
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+ break
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+ else:
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+ is_string = False
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+ if is_string:
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+ if count == 1:
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+ return TYPE_STRING, strings[0]
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+ else:
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+ return TYPE_STRING, strings[:-1]
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+ if size % 4:
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+ if size == 1:
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+ return TYPE_BYTE, bytes[0]
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+ else:
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+ return TYPE_BYTE, list(bytes)
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+ val = []
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+ for i in range(0, size, 4):
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+ val.append(bytes[i:i + 4])
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+ if size == 4:
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+ return TYPE_INT, val[0]
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+ else:
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+ return TYPE_INT, val
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+
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+ def GetEmpty(self, type):
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+ """Get an empty / zero value of the given type
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+
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+ Returns:
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+ A single value of the given type
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+ """
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+ if type == TYPE_BYTE:
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+ return chr(0)
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+ elif type == TYPE_INT:
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+ return struct.pack('<I', 0);
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+ elif type == TYPE_STRING:
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+ return ''
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+ else:
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+ return True
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+
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+ def GetOffset(self):
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+ """Get the offset of a property
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+
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+ This can be implemented by subclasses.
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+
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+ Returns:
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+ The offset of the property (struct fdt_property) within the
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+ file, or None if not known.
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+ """
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+ return None
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-class Node:
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+class NodeBase:
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"""A device tree node
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Properties:
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@@ -89,32 +168,42 @@ class Node:
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Keyed by property name
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"""
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def __init__(self, fdt, offset, name, path):
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- self.offset = offset
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+ self._fdt = fdt
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+ self._offset = offset
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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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+ def _FindNode(self, name):
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+ """Find a node given its name
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+
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+ Args:
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+ name: Node name to look for
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+ Returns:
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+ Node object if found, else None
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+ """
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+ for subnode in self.subnodes:
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+ if subnode.name == name:
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+ return subnode
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+ return None
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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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+ """Scan the subnodes of a node
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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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+ This should be implemented by subclasses
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"""
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- self.props = self._fdt.GetProps(self.path)
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+ raise NotImplementedError()
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- offset = libfdt.fdt_first_subnode(self._fdt.GetFdt(), self.offset)
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- while offset >= 0:
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- sep = '' if self.path[-1] == '/' else '/'
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- name = libfdt.Name(self._fdt.GetFdt(), offset)
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- path = self.path + sep + name
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- node = Node(self._fdt, offset, name, path)
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- self.subnodes.append(node)
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+ def DeleteProp(self, prop_name):
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+ """Delete a property of a node
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- node.Scan()
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- offset = libfdt.fdt_next_subnode(self._fdt.GetFdt(), offset)
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+ This should be implemented by subclasses
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+ Args:
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+ prop_name: Name of the property to delete
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+ """
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+ raise NotImplementedError()
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class Fdt:
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"""Provides simple access to a flat device tree blob.
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@@ -123,26 +212,20 @@ class Fdt:
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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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- with open(fname) as fd:
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- self._fdt = fd.read()
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-
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- def GetFdt(self):
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- """Get the contents of the FDT
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+ self._fname = fname
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- Returns:
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- The FDT contents as a string of bytes
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- """
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- return self._fdt
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-
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- def Scan(self):
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+ def Scan(self, root='/'):
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"""Scan a device tree, building up a tree of Node objects
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This fills in the self._root property
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+
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+ Args:
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+ root: Ignored
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+
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+ TODO(sjg@chromium.org): Implement the 'root' parameter
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"""
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- self._root = Node(self, 0, '/', '/')
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+ self._root = self.Node(self, 0, '/', '/')
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self._root.Scan()
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def GetRoot(self):
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@@ -153,28 +236,34 @@ class Fdt:
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"""
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return self._root
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- def GetProps(self, node):
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- """Get all properties from a node.
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+ def GetNode(self, path):
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+ """Look up a node from its path
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Args:
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- node: Full path to node name to look in.
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-
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+ path: Path to look up, e.g. '/microcode/update@0'
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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 Prop objects.
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+ Node object, or None if not found
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+ """
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+ node = self._root
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+ for part in path.split('/')[1:]:
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+ node = node._FindNode(part)
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+ if not node:
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+ return None
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+ return node
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+
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+ def Flush(self):
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+ """Flush device tree changes back to the file
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+
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+ If the device tree has changed in memory, write it back to the file.
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+ Subclasses can implement this if needed.
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+ """
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+ pass
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+
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+ def Pack(self):
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+ """Pack the device tree down to its minimum size
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- Raises:
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- ValueError: if the node does not exist.
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+ When nodes and properties shrink or are deleted, wasted space can
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+ build up in the device tree binary. Subclasses can implement this
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+ to remove that spare space.
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"""
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- offset = libfdt.fdt_path_offset(self._fdt, node)
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- if offset < 0:
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- libfdt.Raise(offset)
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- props_dict = {}
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- poffset = libfdt.fdt_first_property_offset(self._fdt, offset)
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- while poffset >= 0:
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- dprop, plen = libfdt.fdt_get_property_by_offset(self._fdt, poffset)
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- prop = Prop(libfdt.String(self._fdt, dprop.nameoff), libfdt.Data(dprop))
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- props_dict[prop.name] = prop
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-
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- poffset = libfdt.fdt_next_property_offset(self._fdt, poffset)
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- return props_dict
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+ pass
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