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bc1dea3656
These functions are currently in a separate fdt_util file. Since they are only used from PropBase and subclasses, it makes sense for them to be in the PropBase class. Move these functions into fdt.py along with the list of types. Signed-off-by: Simon Glass <sjg@chromium.org>
134 lines
3.9 KiB
Python
134 lines
3.9 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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# 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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# 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 PropBase:
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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):
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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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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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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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class NodeBase:
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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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class Fdt:
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"""Provides simple access to a flat device tree blob.
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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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