dm: Add a more efficient libfdt library

Add a Python version of the libfdt library which contains enough features to
support the dtoc tool. This is only a very bare-bones implementation. It
requires the 'swig' to build.

Signed-off-by: Simon Glass <sjg@chromium.org>

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