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Diffstat (limited to 'tools/dtoc/fdt.py')
| -rw-r--r-- | tools/dtoc/fdt.py | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/tools/dtoc/fdt.py b/tools/dtoc/fdt.py new file mode 100644 index 0000000000..1d913a925e --- /dev/null +++ b/tools/dtoc/fdt.py @@ -0,0 +1,180 @@ +#!/usr/bin/python +# +# Copyright (C) 2016 Google, Inc +# Written by Simon Glass <sjg@chromium.org> +# +# SPDX-License-Identifier: GPL-2.0+ +# + +import fdt_util +import libfdt +import sys + +# This deals with a device tree, presenting it as a list of Node and Prop +# objects, representing nodes and properties, respectively. +# +# This implementation uses a libfdt Python library to access the device tree, +# so it is fairly efficient. + +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, name, bytes): + self.name = name + self.value = None + if not bytes: + self.type = fdt_util.TYPE_BOOL + self.value = True + return + self.type, self.value = fdt_util.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 = fdt_util.GetEmpty(self.type) + while len(self.value) < len(newprop.value): + self.value.append(val) + + +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, offset, name, path): + self.offset = offset + self.name = name + self.path = path + self._fdt = fdt + self.subnodes = [] + self.props = {} + + 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.path) + + offset = libfdt.fdt_first_subnode(self._fdt.GetFdt(), self.offset) + while offset >= 0: + sep = '' if self.path[-1] == '/' else '/' + name = libfdt.Name(self._fdt.GetFdt(), offset) + path = self.path + sep + name + node = Node(self._fdt, offset, name, path) + self.subnodes.append(node) + + node.Scan() + offset = libfdt.fdt_next_subnode(self._fdt.GetFdt(), offset) + + +class Fdt: + """Provides simple access to a flat device tree blob. + + Properties: + fname: Filename of fdt + _root: Root of device tree (a Node object) + """ + + def __init__(self, fname): + self.fname = fname + with open(fname) as fd: + self._fdt = fd.read() + + def GetFdt(self): + """Get the contents of the FDT + + Returns: + The FDT contents as a string of bytes + """ + return self._fdt + + def Scan(self): + """Scan a device tree, building up a tree of Node objects + + This fills in the self._root property + """ + self._root = Node(self, 0, '/', '/') + self._root.Scan() + + def GetRoot(self): + """Get the root Node of the device tree + + Returns: + The root Node object + """ + return self._root + + 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. + """ + offset = libfdt.fdt_path_offset(self._fdt, node) + if offset < 0: + libfdt.Raise(offset) + props_dict = {} + poffset = libfdt.fdt_first_property_offset(self._fdt, offset) + while poffset >= 0: + dprop, plen = libfdt.fdt_get_property_by_offset(self._fdt, poffset) + prop = Prop(libfdt.String(self._fdt, dprop.nameoff), libfdt.Data(dprop)) + props_dict[prop.name] = prop + + poffset = libfdt.fdt_next_property_offset(self._fdt, poffset) + return props_dict |