#!/usr/bin/env python
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# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
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# Use of this source code is governed by a BSD-style license that can be
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# found in the LICENSE file.
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'''Chrome OS device GPIO library
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This module provides a convenient way to detect, setup, and access to GPIO
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values on a Chrome OS compatible device.
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See help(Gpio) for more information.
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'''
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import os, shutil, sys, tempfile
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class Gpio(object):
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'''
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Utility to access GPIO values.
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Usage:
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gpio = Gpio()
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try:
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gpio.setup()
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print gpio.read(gpio.DEVELOPER_SWITCH_CURRENT)
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except:
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print "gpio failed"
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'''
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# GPIO property names (by "crossystem"):
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DEVELOPER_SWITCH_CURRENT = 'devsw_cur'
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RECOVERY_BUTTON_CURRENT = 'recoverysw_cur'
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WRITE_PROTECT_CURRENT = 'wpsw_cur'
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DEVELOPER_SWITCH_BOOT = 'devsw_boot'
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RECOVERY_BUTTON_BOOT = 'recoverysw_boot'
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WRITE_PROTECT_BOOT = 'wpsw_boot'
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def __init__(self, exception_type=IOError):
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self._exception_type = exception_type
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# list of property conversions, usually str2int.
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self._override_map = {
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self.DEVELOPER_SWITCH_CURRENT: int,
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self.DEVELOPER_SWITCH_BOOT: int,
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self.RECOVERY_BUTTON_CURRENT: int,
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self.RECOVERY_BUTTON_BOOT: int,
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self.WRITE_PROTECT_CURRENT: int,
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self.WRITE_PROTECT_BOOT: int,
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}
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# list of legacy (chromeos_acpi) property names.
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self._legacy_map = {
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'developer_switch': self.DEVELOPER_SWITCH_CURRENT,
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'recovery_button': self.RECOVERY_BUTTON_CURRENT,
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'write_protect': self.WRITE_PROTECT_CURRENT,
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}
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def setup(self):
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'''Configures system for processing GPIO.
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Returns:
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Raises an exception if gpio_setup execution failed.
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'''
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# This is the place to do any configuration / system detection.
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# Currently "crossystem" handles everything so we don't need to do
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# anything now.
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pass
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def read(self, name):
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'''Reads a GPIO property value.
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Check "crossystem" command for the list of available property names.
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Parameters:
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name: the name of property to read.
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Returns: current value, or raise exceptions.
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'''
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debug_title = "Gpio.read('%s'): " % name
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# convert legacy names
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if name in self._legacy_map:
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name = self._legacy_map[name]
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temp_fd, temp_file = tempfile.mkstemp()
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os.close(temp_fd)
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command = "crossystem %s 2>%s" % (name, temp_file)
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pipe = os.popen(command, 'r')
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value = pipe.read()
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exit_status = pipe.close()
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if exit_status:
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with open(temp_file, 'r') as temp_handle:
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debug_info = temp_handle.read()
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value = value.strip()
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debug_info = debug_info.strip()
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if value:
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debug_info = value + '\n' + debug_info
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if debug_info:
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debug_info = '\nInformation: ' + debug_info
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raise self._exception_type(
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debug_title + "Command failed (%d): %s%s" %
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(exit_status, command, debug_info))
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# convert values
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if name in self._override_map:
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try:
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value = self._override_map[name](value)
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except:
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raise self._exception_type(debug_title +
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'Conversion failed: %s' % value)
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return value
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def main():
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gpio = Gpio()
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try:
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gpio.setup()
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print ("developer switch current status: %s" %
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gpio.read(gpio.DEVELOPER_SWITCH_CURRENT))
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except Exception, e:
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print "GPIO failed. %s" % e
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sys.exit(1)
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if __name__ == '__main__':
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main()
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