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This Python library provides a way to access the contents of the device tree. It uses fdtget, so is inefficient for larger device tree files. Signed-off-by: Simon Glass <sjg@chromium.org>
87 lines
2.1 KiB
Python
87 lines
2.1 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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# 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 BytesToValue(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(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 fdt32_to_cpu(val):
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"""Convert a device tree cell to an integer
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Args:
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Value to convert (4-character string representing the cell value)
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Return:
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A native-endian integer value
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"""
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return struct.unpack(">I", val)[0]
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