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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-3102F778-DD2F-4C87-A0DF-7FA44C9709D8" xml:lang="en"><title>Multiple |
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13 Client Support</title><shortdesc>This document describes how multiple clients can access a driver |
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14 over a single logical channel.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
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15 <p>A single channel has a single handle which is shared by driver users. A |
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16 driver can allow or prevent the sharing of a handle to a logical channel between |
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17 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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18 The default implementation does not restrict sharing of the channel, but a |
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19 driver can override the function to change this. </p> |
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20 <p>In the following example, the driver ensures that only the intended clients |
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21 can get the handle and access the driver. Any other client that tries to share |
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22 the handle gets a <codeph>KErrAccessDenied</codeph> error. </p> |
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23 <codeblock id="GUID-2FEB04B3-ABD3-58E4-BFDB-0AD947BA6E16" xml:space="preserve">TInt DExDriverLogicalChannel::RequestUserHandle(DThread* aThread, |
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24 TOwnerType aType) |
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25 { |
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26 // Handle should be provided only to the intended client. Any |
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27 // other clients that try to get a handle to the driver should get an access |
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28 // denied error. |
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29 if ( aType!=EOwnerThread || aThread!=iClient) |
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30 return KErrAccessDenied; |
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31 return KErrNone; |
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32 }</codeblock> |
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33 <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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34 the user from sharing or duplicating an existing channel. It does not restrict |
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35 another process from opening its own separate channel on the same device. </p> |
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36 <p> <note> More than one user can access the driver at the same time. It is |
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37 up to the driver to manage and provide correct and secure access to the driver. </note></p> |
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38 </conbody></concept> |