A script for accessing reboot info in CMOS.

src/platform/utils/reboot_mode.py

Index: src/platform/utils/reboot_mode.py
diff --git a/src/platform/utils/reboot_mode.py b/src/platform/utils/reboot_mode.py
new file mode 100755
index 0000000000000000000000000000000000000000..18f336fd565a9a047f3d7b0456cc7826ef2754fd
--- /dev/null
+++ b/src/platform/utils/reboot_mode.py
@@ -0,0 +1,171 @@
+#!/usr/bin/python
+
+# Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""A script to manipulate ChromeOS CMOS reboot Field.
+
+A few bits in a byte in CMOS (called RDB, short for 'Reboot Data Byte'
+hereafter) are dedicated to information exchange between Linux and BIOS.
+
+The CMOS contents are available through /dev/nvrom. The location of RDB is
+reported by BIOS through ACPI. The few bits in RDB operated on by this script
+are defined in the all_mode_fields dictionary below along with their
+functions.
+
+When invoked without parameters this script prints values of the fields. When
+invoked with any of the bit field names as parameter(s), the script sets the
+bit(s) as required.
+
+Additional parameters allow to specify alternative ACPI and NVRAM files for
+testing.
+"""
+
+__author__ = 'The Chromium OS Authors'
+
+import optparse
+import sys
+
+class RebootModeError(Exception):
+  pass
+
+# global variables
+parser = optparse.OptionParser()
+acpi_file = '/sys/devices/platform/chromeos_acpi/CHNV'
+nvram_file = '/dev/nvram'
+
+# Offset of RDB in NVRAM
+rdb_offset = 0
+
+# NVRAM contents read on startup
+rdb_value = ''
+
+# All bitfields in RDB this script provides access to. Field names prepended
+# by `--' become this script's command line options
+all_mode_fields = {
+    'recovery' : 0x80,
+    'debug_reset' : 0x40,
+    'try_firmware_b': 0x20
+    }
+
+# A dictionary of fields to be updated as requested by the command line
+# parameters
+fields_to_set = {}
+
+
+def OptionHandler(option, opt_str, value, p):
+  """Process bit field name command line parameter.
+
+  Verifies that the value is in range (0 or 1) and adds the appropriate
+  element to fields_to_set dictionary. Should the same field specified in the
+  command line more than once, only the last value will be used.
+
+  Raises:
+    RebootModeError in case the parameter value is out of range.
+  """
+
+  global fields_to_set
+  key = opt_str[2:]
+  if value < 0 or value > 1:
+    raise RebootModeError('--%s should be either 0 or 1' % key)
+
+  fields_to_set[key] = value
+
+
+def PrepareOptions():
+  global parser
+  for field in all_mode_fields:
+    parser.add_option('--' + field, action='callback', type='int',
+                      callback=OptionHandler)
+  parser.add_option('--acpi_file', dest='acpi_file')
+  parser.add_option('--nvram_file', dest='nvram_file')
+
+
+def ParseOptions():
+  global acpi_file
+  global nvram_file
+  (opts, args) = parser.parse_args()
+
+  if opts.acpi_file is not None:
+    acpi_file = opts.acpi_file
+
+  if opts.nvram_file is not None:
+    nvram_file = opts.nvram_file
+
+
+def GetRDBOffset():
+  global rdb_offset
+  try:
+    f = open(acpi_file, 'r')
+    rdb_offset = int(f.read())
+    f.close()
+  except IOError, e:
+    raise RebootModeError('Trying to read %s got this: %s' % (acpi_file, e))
+  except ValueError:
+    raise RebootModeError('%s contents are corrupted' % acpi_file)
+
+
+def ReadNvram():
+  global rdb_value
+  try:
+    f = open(nvram_file, 'rb')
+    f.seek(rdb_offset)
+    rdb_value = ord(f.read(1)[0])
+    f.close()
+  except IOError, e:
+    if e[0] == 2:
+      raise RebootModeError(
+          '%s does not exist. Is nvram module installed?' % nvram_file)
+    if e[0] == 13:
+      raise RebootModeError('Access to %s denied. Are you root?' % nvram_file)
+    raise RebootModeError(e[1])
+  except IndexError, e:
+    raise RebootModeError('Failed reading mode byte from %s' % nvram_file)
+
+
+def PrintCurrentMode():
+  print 'Current reboot mode settings:'
+  for (field, mask) in all_mode_fields.iteritems():
+    print '%-15s: %d' % (field, int(not not (rdb_value & mask)))
+
+
+def SetNewMode():
+  new_mode = 0
+  updated_bits_mask = 0
+
+  for (opt, value) in fields_to_set.iteritems():
+    mask = all_mode_fields[opt]
+    if value:
+      new_mode |= mask
+    updated_bits_mask |= mask
+
+  if (rdb_value & updated_bits_mask) == new_mode:
+    print 'No update required'
+    return
+
+  f = open(nvram_file, 'rb+')
+  f.seek(rdb_offset)
+  new_mode |= (rdb_value & ~updated_bits_mask)
+  f.write('%c' % new_mode)
+  f.close()
+
+
+def DoRebootMode():
+  PrepareOptions()
+  ParseOptions()
+  GetRDBOffset()
+  ReadNvram()
+  if fields_to_set:
+    SetNewMode()
+  else:
+    PrintCurrentMode()
+
+
+if __name__ == '__main__':
+  try:
+    DoRebootMode()
+  except RebootModeError, e:
+    print >> sys.stderr, '%s: %s' % (sys.argv[0].split('/')[-1], e)
+    sys.exit(1)
+  sys.exit(0)