README.md

Chrome OS Power Management

The Chrome OS power manager consists of several components:

powerd: C++ system daemon running as the power user that initiates dimming the screen, suspending the system, etc.
powerd_setuid_helper: setuid root binary used by powerd to perform actions requiring additional privileges.
powerd_dbus_suspend: shell script executed by powerd (by way of powerd_setuid_helper) to suspend and resume the system.
send_metrics_on_resume: shell script executed by powerd_suspend and by the send-boot-metrics Upstart job to report suspend-related metrics.

The docs/ subdirectory contains additional documentation. Along with answers to frequently-asked questions, the following information is available:

Battery Notifications describes when low-battery notifications are shown by the UI.
Inactivity Delays describes powerd's logic for taking action (e.g. dimming the backlight or suspending) when the user is inactive.
Input describes how powerd handles input events.
Keyboard Backlight describes powerd's logic for controlling the keyboard backlight.
Logging describes where and how powerd logs informative messages.
Power Buttons describes how power buttons work.
Power Supplies describes powerd's logic for determining the state of power supplies (e.g. batteries or line power).
Screen Brightness describes powerd's logic for controlling the display backlight.
Shutdown and Reboot describes why and how Chrome OS systems shut down and reboot.
Suspend and Resume describes powerd's process for suspending and resuming the system.
udev Usage describes how powerd uses the udev system to learn about hardware changes.

This repository contains the following subdirectories:

Subdirectory	Description
`common`	Code shared between powerd and tools
`dbus`	D-Bus policy configuration files
`default_prefs`	Default pref files installed to `/usr/share/power_manager`
`docs`	Detailed documentation in Markdown format
`init/shared`	Scripts shared between Upstart and systemd
`init/systemd`	systemd-specific config files
`init/upstart`	Upstart-specific config files installed to `/etc/init`
`optional_prefs`	Pref files conditionally installed based on USE flags
`powerd`	Power manager daemon
`powerd/policy`	High-level parts of powerd that make policy decisions
`powerd/system`	Low-level parts of powerd that communicate with the kernel
`tools`	Utility programs; may depend on `powerd` code
`udev`	udev configuration files and scripts