<?xml version="1.0" encoding="utf-8"?>+
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<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->+
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<!-- This component and the accompanying materials are made available under the terms of the License +
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"Eclipse Public License v1.0" which accompanies this distribution, +
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and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->+
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<!-- Initial Contributors:+
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    Nokia Corporation - initial contribution.+
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Contributors: +
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-->+
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<!DOCTYPE concept+
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  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">+
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<concept id="GUID-3102F778-DD2F-4C87-A0DF-7FA44C9709D8" xml:lang="en"><title>Multiple+
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Client Support</title><shortdesc>This document describes how multiple clients can access a driver+
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over a single logical channel.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>+
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<p>A single channel has a single handle which is shared by driver users. A+
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driver can allow or prevent the sharing of a handle to a logical channel between+
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multiple users. This policy is implemented by the <xref href="GUID-A3CC1D95-4681-3349-A67C-F113A614041D.dita#GUID-A3CC1D95-4681-3349-A67C-F113A614041D/GUID-9E23019E-7383-371E-B63C-85500F6B653D"><apiname>DLogicalChannel::RequestUserHandle()</apiname></xref> function.+
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The default implementation does not restrict sharing of the channel, but a+
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driver can override the function to change this. </p>+
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<p>In the following example, the driver ensures that only the intended clients+
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can get the handle and access the driver. Any other client that tries to share+
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the handle gets a <codeph>KErrAccessDenied</codeph> error. </p>+
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<codeblock id="GUID-2FEB04B3-ABD3-58E4-BFDB-0AD947BA6E16" xml:space="preserve">TInt DExDriverLogicalChannel::RequestUserHandle(DThread* aThread,+
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        TOwnerType aType)+
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    {+
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    // Handle should be provided only to the intended client. Any +
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    // other clients that try to get a handle to the driver should get an access +
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    // denied error.+
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    if ( aType!=EOwnerThread || aThread!=iClient)+
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        return KErrAccessDenied;+
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    return KErrNone;+
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    }</codeblock>+
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<p> <xref href="GUID-A3CC1D95-4681-3349-A67C-F113A614041D.dita#GUID-A3CC1D95-4681-3349-A67C-F113A614041D/GUID-9E23019E-7383-371E-B63C-85500F6B653D"><apiname>DLogicalChannel::RequestUserHandle()</apiname></xref> only restricts+
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the user from sharing or duplicating an existing channel. It does not restrict+
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another process from opening its own separate channel on the same device. </p>+
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<p> <note> More than one user can access the driver at the same time. It is+
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up to the driver to manage and provide correct and secure access to the driver. </note></p>+
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</conbody></concept>+
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