client/site_tests/hardware_Backlight/hardware_Backlight.py

# 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.

from autotest_lib.client.bin import test
from autotest_lib.client.bin import utils
from autotest_lib.client.common_lib import error

def backlight_tool(args):
    cmd = 'backlight-tool %s' % args
    return utils.system_output(cmd)

class hardware_Backlight(test.test):
    version = 1

    def run_once(self):
        # If powerd is running, stop it, so that it cannot interfere with the
        # backlight adjustments in this test.
        if utils.system_output('status powerd').find('start/running') != -1:
            powerd_running = True
            utils.system_output('stop powerd')
        else:
            powerd_running = False

        try:
            brightness = int(backlight_tool("--get_brightness").rstrip())
        except error.CmdError, e:
            raise error.TestFail('Cannot get brightness with backlight-tool')
        max_brightness = int(backlight_tool("--get_max_brightness").rstrip())
        try:
            for i in range(max_brightness + 1):
                backlight_tool("--set_brightness %d" % i)
                result = int(backlight_tool("--get_brightness").rstrip())
                if i != result:
                    raise error.TestFail('Adjusting backlight should change ' \
                                         'actual brightness')
        finally:
            backlight_tool("--set_brightness %d" % brightness)

        # Restore powerd if it was originally running.
        if powerd_running:
            utils.system_output('start powerd');