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Integrating Drivers and Applications with Windows Power Management. Pat Stemen patste @ microsoft.com Program Manager Microsoft Corporation. Agenda. Vista Power Management Goals Realizing Maximum Energy Savings New Power Management Usage Models Changes for Applications and Drivers

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integrating drivers and applications with windows power management

Integrating Drivers and Applications with Windows Power Management

Pat Stemen

patste @ microsoft.com

Program Manager

Microsoft Corporation

agenda
Agenda
  • Vista Power Management Goals
  • Realizing Maximum Energy Savings
  • New Power Management Usage Models
  • Changes for Applications and Drivers
  • Integrating Devices or Applications with Windows Power Manager
  • Handling Common Power Events
  • Summary / Next Steps
vista power management goals
Vista Power Management Goals
  • Simplify the user experience
  • Enhance and extend power management usage models
  • Improve the reliability of sleep transitions
    • Predictable behavior
    • Visibility into power management actions
    • Extensive diagnostic tracing
  • Enable maximum energy savings
    • Mobile PC battery life
    • Desktop power consumption
enabling maximum pc energy savings
Enabling Maximum PC Energy Savings
  • Vista will, by default, enable energy saving features on desktop PCs
    • Monitor display blanking
    • Idle system sleep timeout
  • Vista will default to aggressive power policy defaults for mobile PCs on battery power
  • Vista addresses the principle power management adoption blockers
    • Offers easy power policy configuration
    • Removes need to be Administrator to change policy settings
    • Supports Group Policy control of power settings
    • Provides a rich power policy command-line tool
    • Features reliable and deterministic sleep transitions
simplifying power policy settings
Simplifying Power Policy Settings
  • Vista provides three default power schemes
    • Maximum Energy Savings
    • Automatic
    • Maximum Performance
  • The default power schemes are the personalities for all power schemes
    • Personality indicates the power saving behavior of the scheme
    • Active power scheme personality can be broadcast to interested components
    • Allows applications and devices to understand and respond to user’s power intent
  • Power schemes can be easily discovered and changed by users
    • Via enhanced battery meter
      • Provides a simple, 1st tier interface to power schemes
      • Links to Power Options for advanced settings
new power management usage models
New Power Management Usage Models
  • Hybrid Sleep
    • Addresses user confusion between Standby and Hibernate
      • Users do not always know when standby or hibernate is appropriate
      • Enables single “Off” choice for users
    • Saves Hibernate file, then enters Standby
    • Normally, resume is from memory image
      • Typically 2-3 seconds
    • If power is lost, system resumes from hibernate image on disk
      • Typically 5-10 seconds
new power management usage models1
New Power Management Usage Models
  • Hybrid Sleep Benefits:
    • Allows for a simple shutdown metaphor
      • Users do not need to understand or choose between Standby and Hibernate; just “Off”
    • Provides increased reliability
      • Data and system state are always backed by non-volatile storage
    • Enables Quick Doze to hibernate
      • Eliminates S0 transition on S3->S4 doze timeout
        • System can simply be turned off
new power management usage models2
New Power Management Usage Models
  • Media PCs may benefit from a Consumer Electronics (CE) On / Off model
  • Requires fast response to user On / Off requests
    • Similar to TV remote control
  • PC may need to continue to operate even though the user is done with it
    • Recording or buffering live TV
    • Acting as a media server to other devices
new power management usage models3
New Power Management Usage Models
  • Away Mode addresses this scenario
  • Away Mode is not a power policy or new power state
    • User is not interacting with the machine
    • PC looks and sounds off, but work may continue in the background
    • Goes dark and quiet immediately on user request
new power management usage models4
New Power Management Usage Models
  • Away Mode Details
    • Registry-based configuration
      • OEMs can enable Away Mode during pre-installation
    • When enabled, any Standby request maps to Away Mode
    • Attributes
      • Video is blanked
      • Audio is muted
      • Keyboard / mouse input is filtered
      • System remains in S0 (working state)
      • May still idle to Sleep, based on power policy, usage
new power management usage models5
New Power Management Usage Models
  • Vista power management goals require extensive use of sleep and resume
    • Maximizing PC energy savings requires reliable sleep transitions
  • But, failed transitions are the primary sleep adoption blocker
    • Component vetoes are the primary cause
      • Roughly 1/3 of all sleep failures
      • Drivers may veto sleep requests
      • Services may silently fail sleep
      • Some applications display warnings, some do not
      • Some may display warnings – with the laptop lid closed!
new power management usage models6
New Power Management Usage Models
  • Component vetoes lead to great user frustration and distrust of power management
    • System did not do what the user asked
  • Worst case scenario:
    • Laptop in a bag fails to sleep, or wakes and fails to return to sleep
    • Battery drains, system overheats, laptop is unusable when needed, possible data loss
    • Users turn off sleep and use shutdown
new power management usage models7
New Power Management Usage Models
  • Investigations show that applications and services abuse the ability to veto
    • Veto instead of develop and test for power management
    • Veto to prevent potential network connectivity loss
      • Same component many handle network connectivity well outside of sleep / resume
    • Microsoft testing shows most components do not need sleep query
new power management usage models8
New Power Management Usage Models
  • Reducing component vetoes
    • Vista will not query user mode components when entering sleep
      • User-mode query (PBT_APMQUERYSUSPEND) event will not be sent
        • Regardless of how the sleep transition starts
        • Hardware button press, lid switch, UI, system idle timer
      • User-mode notification (PBT_APMSUSPEND) event will continue to be sent
        • Timeout to process event has been reduced from 20 seconds to 2 seconds
changes for applications and drivers
Changes for Applications and Drivers
  • Applications and Services
    • Do not depend on blocking a sleep state transition
      • Use the PBT_APMSUSPEND event to do any limited cleanup before suspend
        • Cleanup must be completed within 2 seconds
    • A message will always be sent when the system resumes
      • PBT_APMRESUME, PBT_APMRESUMECRITICAL, PBT_APMRESUMEAUTOMATIC
      • Use this message to automatically restart a task that did not complete because of a sleep state transition
changes for applications and drivers1
Changes for Applications and Drivers
  • Applications and Services
    • Applications may temporarily disable sleep idle timers when needed to ensure system availability
      • e.g., Burning a CD, recording a TV show
    • SetThreadExecutionState
      • Temporarily disables the sleep idle timer
      • Does not prevent user-initiated sleep transitions
    • Usage:
      • Call SetThreadExecutionState(ES_CONTINUOUS | ES_SYSTEM_REQUIRED)
        • Disables the sleep idle timer
      • Process the task
      • When complete, call SetThreadExecutionState(ES_CONTINUOUS)
        • Re-enables the sleep idle timer
changes for applications and drivers2
Changes for Applications and Drivers
  • Applications and Services
    • Handling Away Mode notifications
      • Media or other applications should register for Away Mode notification
      • When the user directs the system into Away Mode..
        • Screen and Audio are off
        • Don’t render graphics, audio to local devices
          • Conserves system resources and power
        • Don’t rely on prompting the user for input
changes for applications and drivers3
Changes for Applications and Drivers
  • Drivers
    • Hybrid Sleep
      • Most drivers will not need to be modified for hybrid sleep
      • Drivers are told the platform is entering the S4 state
        • IRP_MN_SET_POWER Parameters.Power.State == PowerSystemHibernate
        • Drivers should save appropriate context for S4, not S3
        • Assume the system may resume from the S4 state
      • Test your device and driver with Vista to ensure compatibility
changes for applications and drivers4
Changes for Applications and Drivers
  • Drivers
    • Hybrid Sleep
      • Wake-enabled devices must support wake from S4
        • Sleep can not be “lightened” for hybrid sleep transitions
        • “Lightened” sleep occurs when system enters S1 instead of S3 due to wake-enabled devices
integrating with windows power policy
Integrating with Windows Power Policy
  • Vista enables all components to integrate with system-wide power policy, including device drivers and software applications
    • Enables rich device power management
      • Beyond run time idle detection
    • Extends current policy preference to components
      • Provides mechanisms for definition and installation of custom power settings
    • Exposes a broad set of power event notifications
integrating with windows power policy1
Integrating with Windows Power Policy
  • To integrate any component with system power policy:
    • Define a new power setting
    • Install the new power setting
    • Register for change notification on the new power setting
    • Respond to change notifications
integrating with windows power policy2
Integrating with Windows Power Policy
  • Define a new power setting
    • New power setting controls the component’s power saving behavior or performance state
    • Specify new power setting attributes
      • Unique GUID
      • Textual description, friendly name
      • Setting values for AC, DC
        • Range of values
        • List of discrete values
    • Specify default values for each default power scheme
      • Specifying the correct defaults for each of the power schemes is critical
      • Users might not go to the Power Control Panel to configure the new setting
integrating with windows power policy3
Integrating with Windows Power Policy
  • Install the new power setting
    • INF or API-based installation
      • INF method is the preferred (and easiest) method
    • New INF directives to support power setting installation
      • Use in device installation INF or separate INF executed during application installation
integrating with windows power policy4
Integrating with Windows Power Policy
  • Register for change notifications on the new power setting
    • Registration APIs available for USER and kernel modes
    • Register within device or application initialization code
      • Register for notification with unique GUID
    • Deregister when your device is stopped or application is closed
    • Kernel-mode registration function includes context parameter
      • Most drivers will pass device extension in context
      • Enables drivers to handle registration for multiple devices
integrating with windows power policy5
Integrating with Windows Power Policy
  • Respond to the power setting change notification
    • Callback is notification to change device performance state or application behavior
      • Callback includes current / new power setting value
      • Actual time of behavior state transition (immediate / delayed) is defined by the driver or application
    • Callback will be executed when the power setting value changes
      • Active power scheme change
      • AC / DC transition
      • User changes setting value
integrating with windows power policy6
Integrating with Windows Power Policy
  • Additional notes
    • Windows power control panel offers single place for power configuration
      • Includes configuration of custom power settings for components integrated with system power policy
    • Look for white paper detailing APIs and power setting installation on the WHDC Web site
      • http://go.microsoft.com/fwlink/?LinkId=51286
handling common power events
Handling Common Power Events
  • Applications may wish to handle common power management events
    • AC / DC power state change
    • Power scheme personality change
    • Monitor on / off
    • User presence (away mode)
  • Historically, applications need to poll for status change
    • Eg, GetSystemPowerStatus API for battery capacity, AC line status
  • Vista features asynchronous notification of common power events
    • Same API used for power setting change registration
    • User mode
      • RegisterPowerSettingNotification()
    • Kernel mode
      • PoRegisterPowerSettingNotification()
handling common power events1
Handling Common Power Events
  • AC / DC power state change
    • Register with GUID_ACDC_POWER_SOURCE
    • Callback value is
      • AC (utility power)
      • DC (battery power)
      • Short-term DC (UPS device)
        • Useful for knowing when the system transitions to UPS power
handling common power events2
Handling Common Power Events
  • Power scheme personality change
    • Register with GUID_POWER_SCHEME_PERSONALITY
    • Callback value is GUID indicating scheme personality
      • Maximum Energy Savings
      • Automatic
      • Maximum Performance
    • Can be used to implement simple power saving behavior
      • Application, driver can change power behavior according to current power scheme personality
      • Does not allow for power behavior configuration in the power control panel
handling common power events3
Handling Common Power Events
  • Monitor on / off
    • Register with GUID_MONITOR_POWER_ON
    • Notification value indicates if the primary video device is on or off
    • Useful for media applications
      • Applications may stop rendering video or other content when the display is off to save power
handling common power events4
Handling Common Power Events
  • Away Mode
    • Register with GUID_SYSTEM_AWAYMODE
      • Value indicates if the user is present or not
    • Notification that the system is entering or exiting Away Mode
summary
Summary
  • Vista power management goal is to make power management simple for users
  • Vista enables power saving settings by default on all PCs
  • Changes to Windows power management and new usage models will impact your application and driver development
  • Vista enables all components to easily integrate with system power policy
  • Vista makes it easy to register and respond to common power management events
next steps
Next Steps
  • Test your application or driver!
    • Register for Vista beta program, provide feedback
    • Test tools available in Windows Driver Kit (WDK)
  • Take advantage of power saving features and opportunities to differentiate your products
  • Integrate your application or driver with system power policy
    • Look for white paper on WHDC
      • http://go.microsoft.com/fwlink/?LinkId=51286
  • Leverage notifications for common power management events in your application or driver
slide35

© 2006 Microsoft Corporation. All rights reserved.

This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.