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![Simon Glass](/assets/img/avatar_default.png)
This file was used to select between the normal and fallback libfdt implementations. Now that we only have one, it is not needed. Drop it and fix up all users. Signed-off-by: Simon Glass <sjg@chromium.org>
409 lines
12 KiB
Python
409 lines
12 KiB
Python
#!/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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import struct
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import sys
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import fdt_util
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import libfdt
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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. You can use
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# FdtScan() as a convenience function to create and scan an Fdt.
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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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# A list of types we support
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(TYPE_BYTE, TYPE_INT, TYPE_STRING, TYPE_BOOL) = range(4)
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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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class Prop:
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"""A device tree property
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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, node, offset, name, bytes):
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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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self.bytes = str(bytes)
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if not bytes:
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self.type = TYPE_BOOL
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self.value = True
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return
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self.type, self.value = self.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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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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def Widen(self, newprop):
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"""Figure out which property type is more general
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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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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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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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if type(newprop.value) == list and type(self.value) != list:
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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 = 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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Args:
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A string containing bytes
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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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bytes = str(bytes)
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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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def GetEmpty(self, type):
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"""Get an empty / zero value of the given type
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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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def GetOffset(self):
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"""Get the offset of a property
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Returns:
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The offset of the property (struct fdt_property) within the file
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"""
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return self._node._fdt.GetStructOffset(self._offset)
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class Node:
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"""A device tree node
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Properties:
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offset: Integer offset in the device tree
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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, offset, name, path):
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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.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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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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def Offset(self):
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"""Returns the offset of a node, after checking the cache
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This should be used instead of self._offset directly, to ensure that
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the cache does not contain invalid offsets.
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"""
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self._fdt.CheckCache()
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return self._offset
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def Scan(self):
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"""Scan a node's properties and subnodes
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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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self.props = self._fdt.GetProps(self)
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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 = self._fdt._fdt_obj.get_name(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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node.Scan()
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offset = libfdt.fdt_next_subnode(self._fdt.GetFdt(), offset)
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def Refresh(self, my_offset):
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"""Fix up the _offset for each node, recursively
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Note: This does not take account of property offsets - these will not
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be updated.
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"""
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if self._offset != my_offset:
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#print '%s: %d -> %d\n' % (self.path, self._offset, my_offset)
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self._offset = my_offset
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offset = libfdt.fdt_first_subnode(self._fdt.GetFdt(), self._offset)
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for subnode in self.subnodes:
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subnode.Refresh(offset)
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offset = libfdt.fdt_next_subnode(self._fdt.GetFdt(), offset)
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def DeleteProp(self, prop_name):
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"""Delete a property of a node
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The property is deleted and the offset cache is invalidated.
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Args:
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prop_name: Name of the property to delete
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Raises:
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ValueError if the property does not exist
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"""
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CheckErr(libfdt.fdt_delprop(self._fdt.GetFdt(), self.Offset(), prop_name),
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"Node '%s': delete property: '%s'" % (self.path, prop_name))
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del self.props[prop_name]
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self._fdt.Invalidate()
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class Fdt:
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"""Provides simple access to a flat device tree blob using libfdts.
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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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def __init__(self, fname):
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self._fname = fname
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self._cached_offsets = False
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if self._fname:
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self._fname = fdt_util.EnsureCompiled(self._fname)
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with open(self._fname) as fd:
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self._fdt = bytearray(fd.read())
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self._fdt_obj = libfdt.Fdt(self._fdt)
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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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Args:
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root: Ignored
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TODO(sjg@chromium.org): Implement the 'root' parameter
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"""
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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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"""Get the root Node of the device tree
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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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def GetNode(self, path):
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"""Look up a node from its path
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Args:
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path: Path to look up, e.g. '/microcode/update@0'
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Returns:
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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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def Flush(self):
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"""Flush device tree changes back to the file
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If the device tree has changed in memory, write it back to the file.
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"""
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with open(self._fname, 'wb') as fd:
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fd.write(self._fdt)
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def Pack(self):
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"""Pack the device tree down to its minimum size
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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.
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"""
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CheckErr(libfdt.fdt_pack(self._fdt), 'pack')
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fdt_len = libfdt.fdt_totalsize(self._fdt)
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del self._fdt[fdt_len:]
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def GetFdt(self):
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"""Get the contents of the FDT
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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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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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def GetProps(self, node):
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"""Get all properties from a node.
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Args:
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node: Full path to node name to look in.
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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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Raises:
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ValueError: if the node does not exist.
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"""
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props_dict = {}
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poffset = libfdt.fdt_first_property_offset(self._fdt, node._offset)
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while poffset >= 0:
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p = self._fdt_obj.get_property_by_offset(poffset)
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prop = Prop(node, poffset, p.name, p.value)
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props_dict[prop.name] = prop
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poffset = libfdt.fdt_next_property_offset(self._fdt, poffset)
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return props_dict
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def Invalidate(self):
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"""Mark our offset cache as invalid"""
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self._cached_offsets = False
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def CheckCache(self):
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"""Refresh the offset cache if needed"""
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if self._cached_offsets:
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return
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self.Refresh()
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self._cached_offsets = True
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def Refresh(self):
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"""Refresh the offset cache"""
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self._root.Refresh(0)
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def GetStructOffset(self, offset):
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"""Get the file offset of a given struct offset
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Args:
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offset: Offset within the 'struct' region of the device tree
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Returns:
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Position of @offset within the device tree binary
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"""
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return libfdt.fdt_off_dt_struct(self._fdt) + offset
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@classmethod
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def Node(self, fdt, offset, name, path):
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"""Create a new node
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This is used by Fdt.Scan() to create a new node using the correct
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class.
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Args:
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fdt: Fdt object
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offset: Offset of node
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name: Node name
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path: Full path to node
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"""
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node = Node(fdt, offset, name, path)
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return node
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def FdtScan(fname):
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"""Returns a new Fdt object from the implementation we are using"""
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dtb = Fdt(fname)
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dtb.Scan()
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return dtb
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