dm: Add a library to provide simple device-tree access
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>
diff --git a/tools/dtoc/fdt_util.py b/tools/dtoc/fdt_util.py
new file mode 100644
index 0000000..929b524
--- /dev/null
+++ b/tools/dtoc/fdt_util.py
@@ -0,0 +1,86 @@
+#!/usr/bin/python
+#
+# Copyright (C) 2016 Google, Inc
+# Written by Simon Glass <sjg@chromium.org>
+#
+# SPDX-License-Identifier: GPL-2.0+
+#
+
+import struct
+
+# A list of types we support
+(TYPE_BYTE, TYPE_INT, TYPE_STRING, TYPE_BOOL) = range(4)
+
+def BytesToValue(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
+ """
+ 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(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 fdt32_to_cpu(val):
+ """Convert a device tree cell to an integer
+
+ Args:
+ Value to convert (4-character string representing the cell value)
+
+ Return:
+ A native-endian integer value
+ """
+ return struct.unpack(">I", val)[0]