| #!/usr/bin/python |
| # SPDX-License-Identifier: GPL-2.0+ |
| # |
| # Copyright (C) 2016 Google, Inc |
| # Written by Simon Glass <sjg@chromium.org> |
| # |
| |
| import struct |
| import sys |
| |
| import fdt_util |
| import libfdt |
| |
| # This deals with a device tree, presenting it as an assortment of Node and |
| # Prop objects, representing nodes and properties, respectively. This file |
| # contains the base classes and defines the high-level API. You can use |
| # FdtScan() as a convenience function to create and scan an Fdt. |
| |
| # This implementation uses a libfdt Python library to access the device tree, |
| # so it is fairly efficient. |
| |
| # A list of types we support |
| (TYPE_BYTE, TYPE_INT, TYPE_STRING, TYPE_BOOL, TYPE_INT64) = range(5) |
| |
| def CheckErr(errnum, msg): |
| if errnum: |
| raise ValueError('Error %d: %s: %s' % |
| (errnum, libfdt.fdt_strerror(errnum), msg)) |
| |
| class Prop: |
| """A device tree property |
| |
| Properties: |
| name: Property name (as per the device tree) |
| value: Property value as a string of bytes, or a list of strings of |
| bytes |
| type: Value type |
| """ |
| def __init__(self, node, offset, name, bytes): |
| self._node = node |
| self._offset = offset |
| self.name = name |
| self.value = None |
| self.bytes = str(bytes) |
| if not bytes: |
| self.type = TYPE_BOOL |
| self.value = True |
| return |
| self.type, self.value = self.BytesToValue(bytes) |
| |
| def GetPhandle(self): |
| """Get a (single) phandle value from a property |
| |
| Gets the phandle valuie from a property and returns it as an integer |
| """ |
| return fdt_util.fdt32_to_cpu(self.value[:4]) |
| |
| def Widen(self, newprop): |
| """Figure out which property type is more general |
| |
| Given a current property and a new property, this function returns the |
| one that is less specific as to type. The less specific property will |
| be ble to represent the data in the more specific property. This is |
| used for things like: |
| |
| node1 { |
| compatible = "fred"; |
| value = <1>; |
| }; |
| node1 { |
| compatible = "fred"; |
| value = <1 2>; |
| }; |
| |
| He we want to use an int array for 'value'. The first property |
| suggests that a single int is enough, but the second one shows that |
| it is not. Calling this function with these two propertes would |
| update the current property to be like the second, since it is less |
| specific. |
| """ |
| if newprop.type < self.type: |
| self.type = newprop.type |
| |
| if type(newprop.value) == list and type(self.value) != list: |
| self.value = [self.value] |
| |
| if type(self.value) == list and len(newprop.value) > len(self.value): |
| val = self.GetEmpty(self.type) |
| while len(self.value) < len(newprop.value): |
| self.value.append(val) |
| |
| def BytesToValue(self, bytes): |
| """Converts a string of bytes into a type and value |
| |
| Args: |
| A string containing bytes |
| |
| Return: |
| A tuple: |
| Type of data |
| Data, either a single element or a list of elements. Each element |
| is one of: |
| TYPE_STRING: string value from the property |
| TYPE_INT: a byte-swapped integer stored as a 4-byte string |
| TYPE_BYTE: a byte stored as a single-byte string |
| """ |
| bytes = str(bytes) |
| size = len(bytes) |
| strings = bytes.split('\0') |
| is_string = True |
| count = len(strings) - 1 |
| if count > 0 and not strings[-1]: |
| for string in strings[:-1]: |
| if not string: |
| is_string = False |
| break |
| for ch in string: |
| if ch < ' ' or ch > '~': |
| is_string = False |
| break |
| else: |
| is_string = False |
| if is_string: |
| if count == 1: |
| return TYPE_STRING, strings[0] |
| else: |
| return TYPE_STRING, strings[:-1] |
| if size % 4: |
| if size == 1: |
| return TYPE_BYTE, bytes[0] |
| else: |
| return TYPE_BYTE, list(bytes) |
| val = [] |
| for i in range(0, size, 4): |
| val.append(bytes[i:i + 4]) |
| if size == 4: |
| return TYPE_INT, val[0] |
| else: |
| return TYPE_INT, val |
| |
| def GetEmpty(self, type): |
| """Get an empty / zero value of the given type |
| |
| Returns: |
| A single value of the given type |
| """ |
| if type == TYPE_BYTE: |
| return chr(0) |
| elif type == TYPE_INT: |
| return struct.pack('<I', 0); |
| elif type == TYPE_STRING: |
| return '' |
| else: |
| return True |
| |
| def GetOffset(self): |
| """Get the offset of a property |
| |
| Returns: |
| The offset of the property (struct fdt_property) within the file |
| """ |
| return self._node._fdt.GetStructOffset(self._offset) |
| |
| class Node: |
| """A device tree node |
| |
| Properties: |
| offset: Integer offset in the device tree |
| name: Device tree node tname |
| path: Full path to node, along with the node name itself |
| _fdt: Device tree object |
| subnodes: A list of subnodes for this node, each a Node object |
| props: A dict of properties for this node, each a Prop object. |
| Keyed by property name |
| """ |
| def __init__(self, fdt, parent, offset, name, path): |
| self._fdt = fdt |
| self.parent = parent |
| self._offset = offset |
| self.name = name |
| self.path = path |
| self.subnodes = [] |
| self.props = {} |
| |
| def _FindNode(self, name): |
| """Find a node given its name |
| |
| Args: |
| name: Node name to look for |
| Returns: |
| Node object if found, else None |
| """ |
| for subnode in self.subnodes: |
| if subnode.name == name: |
| return subnode |
| return None |
| |
| def Offset(self): |
| """Returns the offset of a node, after checking the cache |
| |
| This should be used instead of self._offset directly, to ensure that |
| the cache does not contain invalid offsets. |
| """ |
| self._fdt.CheckCache() |
| return self._offset |
| |
| def Scan(self): |
| """Scan a node's properties and subnodes |
| |
| This fills in the props and subnodes properties, recursively |
| searching into subnodes so that the entire tree is built. |
| """ |
| self.props = self._fdt.GetProps(self) |
| phandle = self.props.get('phandle') |
| if phandle: |
| val = fdt_util.fdt32_to_cpu(phandle.value) |
| self._fdt.phandle_to_node[val] = self |
| |
| offset = libfdt.fdt_first_subnode(self._fdt.GetFdt(), self.Offset()) |
| while offset >= 0: |
| sep = '' if self.path[-1] == '/' else '/' |
| name = self._fdt._fdt_obj.get_name(offset) |
| path = self.path + sep + name |
| node = Node(self._fdt, self, offset, name, path) |
| self.subnodes.append(node) |
| |
| node.Scan() |
| offset = libfdt.fdt_next_subnode(self._fdt.GetFdt(), offset) |
| |
| def Refresh(self, my_offset): |
| """Fix up the _offset for each node, recursively |
| |
| Note: This does not take account of property offsets - these will not |
| be updated. |
| """ |
| if self._offset != my_offset: |
| #print '%s: %d -> %d\n' % (self.path, self._offset, my_offset) |
| self._offset = my_offset |
| offset = libfdt.fdt_first_subnode(self._fdt.GetFdt(), self._offset) |
| for subnode in self.subnodes: |
| subnode.Refresh(offset) |
| offset = libfdt.fdt_next_subnode(self._fdt.GetFdt(), offset) |
| |
| def DeleteProp(self, prop_name): |
| """Delete a property of a node |
| |
| The property is deleted and the offset cache is invalidated. |
| |
| Args: |
| prop_name: Name of the property to delete |
| Raises: |
| ValueError if the property does not exist |
| """ |
| CheckErr(libfdt.fdt_delprop(self._fdt.GetFdt(), self.Offset(), prop_name), |
| "Node '%s': delete property: '%s'" % (self.path, prop_name)) |
| del self.props[prop_name] |
| self._fdt.Invalidate() |
| |
| class Fdt: |
| """Provides simple access to a flat device tree blob using libfdts. |
| |
| Properties: |
| fname: Filename of fdt |
| _root: Root of device tree (a Node object) |
| """ |
| def __init__(self, fname): |
| self._fname = fname |
| self._cached_offsets = False |
| self.phandle_to_node = {} |
| if self._fname: |
| self._fname = fdt_util.EnsureCompiled(self._fname) |
| |
| with open(self._fname) as fd: |
| self._fdt = bytearray(fd.read()) |
| self._fdt_obj = libfdt.Fdt(self._fdt) |
| |
| def Scan(self, root='/'): |
| """Scan a device tree, building up a tree of Node objects |
| |
| This fills in the self._root property |
| |
| Args: |
| root: Ignored |
| |
| TODO(sjg@chromium.org): Implement the 'root' parameter |
| """ |
| self._root = self.Node(self, None, 0, '/', '/') |
| self._root.Scan() |
| |
| def GetRoot(self): |
| """Get the root Node of the device tree |
| |
| Returns: |
| The root Node object |
| """ |
| return self._root |
| |
| def GetNode(self, path): |
| """Look up a node from its path |
| |
| Args: |
| path: Path to look up, e.g. '/microcode/update@0' |
| Returns: |
| Node object, or None if not found |
| """ |
| node = self._root |
| for part in path.split('/')[1:]: |
| node = node._FindNode(part) |
| if not node: |
| return None |
| return node |
| |
| def Flush(self): |
| """Flush device tree changes back to the file |
| |
| If the device tree has changed in memory, write it back to the file. |
| """ |
| with open(self._fname, 'wb') as fd: |
| fd.write(self._fdt) |
| |
| def Pack(self): |
| """Pack the device tree down to its minimum size |
| |
| When nodes and properties shrink or are deleted, wasted space can |
| build up in the device tree binary. |
| """ |
| CheckErr(libfdt.fdt_pack(self._fdt), 'pack') |
| fdt_len = libfdt.fdt_totalsize(self._fdt) |
| del self._fdt[fdt_len:] |
| |
| def GetFdt(self): |
| """Get the contents of the FDT |
| |
| Returns: |
| The FDT contents as a string of bytes |
| """ |
| return self._fdt |
| |
| def CheckErr(errnum, msg): |
| if errnum: |
| raise ValueError('Error %d: %s: %s' % |
| (errnum, libfdt.fdt_strerror(errnum), msg)) |
| |
| |
| def GetProps(self, node): |
| """Get all properties from a node. |
| |
| Args: |
| node: Full path to node name to look in. |
| |
| Returns: |
| A dictionary containing all the properties, indexed by node name. |
| The entries are Prop objects. |
| |
| Raises: |
| ValueError: if the node does not exist. |
| """ |
| props_dict = {} |
| poffset = libfdt.fdt_first_property_offset(self._fdt, node._offset) |
| while poffset >= 0: |
| p = self._fdt_obj.get_property_by_offset(poffset) |
| prop = Prop(node, poffset, p.name, p.value) |
| props_dict[prop.name] = prop |
| |
| poffset = libfdt.fdt_next_property_offset(self._fdt, poffset) |
| return props_dict |
| |
| def Invalidate(self): |
| """Mark our offset cache as invalid""" |
| self._cached_offsets = False |
| |
| def CheckCache(self): |
| """Refresh the offset cache if needed""" |
| if self._cached_offsets: |
| return |
| self.Refresh() |
| self._cached_offsets = True |
| |
| def Refresh(self): |
| """Refresh the offset cache""" |
| self._root.Refresh(0) |
| |
| def GetStructOffset(self, offset): |
| """Get the file offset of a given struct offset |
| |
| Args: |
| offset: Offset within the 'struct' region of the device tree |
| Returns: |
| Position of @offset within the device tree binary |
| """ |
| return libfdt.fdt_off_dt_struct(self._fdt) + offset |
| |
| @classmethod |
| def Node(self, fdt, parent, offset, name, path): |
| """Create a new node |
| |
| This is used by Fdt.Scan() to create a new node using the correct |
| class. |
| |
| Args: |
| fdt: Fdt object |
| parent: Parent node, or None if this is the root node |
| offset: Offset of node |
| name: Node name |
| path: Full path to node |
| """ |
| node = Node(fdt, parent, offset, name, path) |
| return node |
| |
| def FdtScan(fname): |
| """Returns a new Fdt object from the implementation we are using""" |
| dtb = Fdt(fname) |
| dtb.Scan() |
| return dtb |
