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+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
+<!-- This component and the accompanying materials are made available under the terms of the License 
+"Eclipse Public License v1.0" which accompanies this distribution, 
+and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
+<!-- Initial Contributors:
+    Nokia Corporation - initial contribution.
+Contributors: 
+-->
+<!DOCTYPE concept
+  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
+<concept id="GUID-0C435514-EEC6-5660-BB5F-535790349632" xml:lang="en"><title>Power Management</title><shortdesc>The kernel provides a framework for managing power within
+the system, and the management of the transition between power states. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
+<p>The kernel-side framework manages the transition between power
+states on the device. A base port can implement a kernel extension
+to interface to the power management hardware that is provided on
+the phone. The framework also provides an interface for device drivers
+to use the power </p>
+<p>The user-side interface to the framework is provided by the Power
+class in the User Library. This allows applications can be notified
+about, and can react to, changes in power state, and indeed can initiate
+changes to power state. The <xref href="GUID-E09E4418-4DC3-56A3-BFBE-486C9C8D25C9.dita">Domain Manager</xref> component provides a way to manage the power needs and dependencies
+of applications. </p>
+<p>In Symbian platform, an initial port of the system does not require
+the existence of a power model. In this sense it is optional, and
+its absence will result in default behaviour provided by Symbian platform.
+However, this is not likely to result in optimal power usage, so the
+development of a power model based on the framework provided by Symbian
+platform will be required for commercial devices. </p>
+<p>The interfaces for power management on the kernel-side are shown
+in the following diagram: </p>
+<fig id="GUID-4020768D-7FDF-58EC-82A7-F98E259046D0">
+<image href="GUID-782E8D92-0431-50F5-95A0-5B231EBDF391_d0e25767_href.png" placement="inline"/>
+</fig>
+<ul>
+<li id="GUID-4E59C261-2025-5402-9EE1-EBC50BCD409F"><p>The power manager
+manages the transition between power states. </p> </li>
+<li id="GUID-B3CD4688-45D0-5F46-A968-2DDD76ABB9B7"><p>The power controller
+is a kernel extension that manages the device-specific power management
+hardware such as an on-chip power management controller, oscillators
+etc. The power controller kernel extension is provided in the base
+port. </p> </li>
+<li id="GUID-07CBC9E9-7A2E-5BB5-95F6-1ECF36B502ED"><p>Power handlers
+are device drivers that interface to the power manager. </p> </li>
+</ul>
+<p>The following sections describes these concepts in more detail. </p>
+<section id="GUID-330F07B2-BBDF-5675-B7D5-FF6B25DD03F4"><title>Power
+manager</title> <p>The power manager manages the transition between
+power states. It co-ordinates the change in the power state of peripherals
+and the CPU (hardware), and provides the necessary interactions with
+the device (peripheral) drivers and the power controller (software).
+It also manages interactions with the user-side model. </p> <p>The
+power manager is an instance of the <codeph>DPowerManager</codeph> class, an object that is private to Symbian platform. This object
+is created when the system is initialised, but is not installed as
+the power manager until the <xref href="GUID-0C435514-EEC6-5660-BB5F-535790349632.dita#GUID-0C435514-EEC6-5660-BB5F-535790349632/GUID-07F53484-4727-5338-9320-DF6A0BB440E4">power controller</xref> has been created and registered. Until the <codeph>DPowerManager</codeph> object is installed as the system's power
+manager, Symbian platform manages power using built-in default behaviour. </p> <p>The user-side uses the <xref href="GUID-15D25C07-CFD2-32CE-AD22-E17D512D8E87.dita"><apiname>Power</apiname></xref> class, a set
+of static functions, as an interface to the power manager. This allows
+the user side to request a transition to the <i>Standby</i> or <i>Off </i> state, and to request notification of wake-up events, i.e.
+events that will cause a transition back to the <i>Active</i> state. </p> <p>The power manager object is the anchor point for the power controller
+object and the power handler objects. </p> </section>
+<section id="GUID-07F53484-4727-5338-9320-DF6A0BB440E4"><title>Power
+controller</title> <p>The power controller manages the device-specific
+power management hardware such as an on-chip power management controller,
+oscillators etc. </p> <p>The power controller is an instance of a <xref href="GUID-B3D1C422-6A82-3C6E-9123-1E4F598F0366.dita"><apiname>DPowerController</apiname></xref> class. This is an abstract class that
+requires an implementation . A concrete implementation supports power
+management hardware that is Variant specific. Typically, the Variant
+creates a power controller object when the Variant is initialised,
+and then registers it with the power manager through a call to <xref href="GUID-B3D1C422-6A82-3C6E-9123-1E4F598F0366.dita#GUID-B3D1C422-6A82-3C6E-9123-1E4F598F0366/GUID-F66D72D0-AA27-3BAF-8915-C6E8CC4E7CCF"><apiname>DPowerController::Register()</apiname></xref>. Registration puts a pointer
+to the <codeph>DPowerController</codeph> object into the Symbian platform
+internal <codeph>DPowerManager</codeph> object. </p> <p>The power
+controller is responsible for tracking wake-up events, notifying the
+power manager of such events through a call to <xref href="GUID-B3D1C422-6A82-3C6E-9123-1E4F598F0366.dita#GUID-B3D1C422-6A82-3C6E-9123-1E4F598F0366/GUID-3524A807-F4A9-3DE4-918A-0C03BE0D1AEF"><apiname>DPowerController::WakeUpEvent()</apiname></xref>. </p> <fig id="GUID-7BBCE70B-381C-5E65-83CF-498B2C6D15DA">
+<image href="GUID-9D8C62FB-1E42-5B69-8ECC-2B68AD7C71A5_d0e25863_href.png" placement="inline"/>
+</fig> </section>
+<section id="GUID-DC5F1ECD-CCA3-59FF-A2F1-A3DBD76CD458"><title>Power
+handlers</title> <p>Device drivers interface to the power manager
+through the <xref href="GUID-761AE02B-41A6-35EA-AA9F-0AEEFF67A6F7.dita"><apiname>DPowerHandler</apiname></xref> class. This is an abstract
+class that requires a concrete implementation by device (peripheral)
+drivers. </p> <p>How a <codeph>DPowerHandler</codeph> object fits
+into a driver's own object model is a matter of individual device
+driver design. However, after construction of this object, the driver
+is expected to register it with the power manager by calling <xref href="GUID-761AE02B-41A6-35EA-AA9F-0AEEFF67A6F7.dita#GUID-761AE02B-41A6-35EA-AA9F-0AEEFF67A6F7/GUID-E8353DF6-B21B-383F-99AB-94B6B5139E47"><apiname>DPowerHandler::Add()</apiname></xref>, after which it will receive notification
+of changes to the power state. </p> <p>The power manager calls <xref href="GUID-761AE02B-41A6-35EA-AA9F-0AEEFF67A6F7.dita#GUID-761AE02B-41A6-35EA-AA9F-0AEEFF67A6F7/GUID-578DB5FB-731D-36B2-A459-AAC7F250D726"><apiname>DPowerHandler::PowerDown()</apiname></xref> when it requests a power state
+transition to either the <i>Off</i> or the <i>Standby</i> state. The
+power manager calls <xref href="GUID-761AE02B-41A6-35EA-AA9F-0AEEFF67A6F7.dita#GUID-761AE02B-41A6-35EA-AA9F-0AEEFF67A6F7/GUID-DDC564B4-BD12-30E9-B04A-DBA6CFAF8743"><apiname>DPowerHandler::PowerUp()</apiname></xref> when
+it requests a power state transition to the <i>Active</i> state. The
+driver must respond to a power transition notification after it has
+dealt with it by calling <xref href="GUID-761AE02B-41A6-35EA-AA9F-0AEEFF67A6F7.dita#GUID-761AE02B-41A6-35EA-AA9F-0AEEFF67A6F7/GUID-BF62042B-FB7B-3D5B-8379-490FBA284A7A"><apiname>DPowerHandler::PowerUpDone()</apiname></xref> or <xref href="GUID-761AE02B-41A6-35EA-AA9F-0AEEFF67A6F7.dita#GUID-761AE02B-41A6-35EA-AA9F-0AEEFF67A6F7/GUID-EBE8CFF8-50BD-3AC3-A4C8-47094DA5674D"><apiname>DPowerHandler::PowerDownDone()</apiname></xref> as appropriate. </p> <fig id="GUID-5A5E8846-DE8A-50FC-9D0E-8D8E88291835">
+<image href="GUID-1BB379B6-C0B5-5099-90A0-1BA39DC2C7DD_d0e25918_href.png" placement="inline"/>
+</fig> </section>
+<section id="GUID-8062EF29-9CE3-5414-9DE2-E494F48F0CFB"><title>Shared
+power sources</title> <note><p>See the <xref href="GUID-2ECF13A1-9D56-5740-A09F-8267E6A45DD9.dita">Power Resource Manager</xref> documentation for more information. </p></note> <p>The set of power sources on a device, how they are connected to peripherals,
+and their power states are totally dependent on the specific device.
+This means that Symbian platform cannot provide a comprehensive API
+for handling such sources. </p> <p>However, Symbian platform does
+provide an interface, <xref href="GUID-10105403-AF16-3908-AE9E-96CF2A03AD3A.dita"><apiname>MPowerInput</apiname></xref>, through which
+drivers register their use of a power source and their release of
+that power source. Symbian platform makes the following recommendations: </p> <ul>
+<li id="GUID-D1B32CB8-E3EF-532C-9771-D5B9CFE3C5DD"><p>Each (shared)
+power source is represented by a separate object. </p> </li>
+<li id="GUID-AA47D3A2-8F3A-5D7D-AB41-8658FF5C9260"><p>The class, or
+class hierarchy, that represents the power source should implement
+the <codeph>MPowerInput</codeph> interface so that device (peripheral)
+drivers can register their use or their release of that power source. </p> </li>
+<li id="GUID-017BC38F-1207-52B8-8B35-D38F66849FC6"><p>Define a custom
+interface with the power controller. It is likely that the Variant
+will be responsible for providing the implementation for the power
+inputs, and for providing this custom interface. </p> </li>
+</ul> <p>Drivers that need power from a specific power source call <xref href="GUID-10105403-AF16-3908-AE9E-96CF2A03AD3A.dita#GUID-10105403-AF16-3908-AE9E-96CF2A03AD3A/GUID-2BCA5312-43D9-3763-9636-3B2EB046D2C1"><apiname>MPowerInput::Use()</apiname></xref> on the object that represents that power
+source. To release dependence on that power source, the driver calls <xref href="GUID-10105403-AF16-3908-AE9E-96CF2A03AD3A.dita#GUID-10105403-AF16-3908-AE9E-96CF2A03AD3A/GUID-606ECD77-A5F7-3408-9B63-C68C0A7B73C6"><apiname>MPowerInput::Release()</apiname></xref>. </p> <p>To represent a shared power
+source, a suggested implementation of <codeph>MPowerInput</codeph> might be to associate a counting value with the power source object.
+A call to <codeph>Use()</codeph> would increment the counter, while
+a call to <codeph>Release()</codeph> would decrement it. On construction
+of the object, the initial value might be 0, indicating that no peripherals
+require power from this source. A value of 1 or higher would indicate
+that one or more peripherals require power from this source. The implementation
+would, therefore, cause this power source to be kept on while at least
+one peripheral needs it; the power source would only be switched off
+when no peripherals need power from it. </p> </section>
+</conbody><related-links>
+<link href="GUID-E09E4418-4DC3-56A3-BFBE-486C9C8D25C9.dita"><linktext>Domain
+Manager</linktext></link>
+<link href="GUID-3773A78D-F491-52EB-AA1D-201636497F28.dita"><linktext>Power
+Management Tutorials</linktext></link>
+<link href="GUID-6E1DE1E4-1B09-541C-8708-9126E69B42CE.dita"><linktext>Power
+Resource Manager (PRM)</linktext></link>
+</related-links></concept>
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