--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Adaptation/GUID-7AB51180-7A1A-40C7-B28F-EA46314A6E5B-GENID-1-2-1-9-1-5-1-4-1.dita	Fri Oct 15 14:32:18 2010 +0100
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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-7AB51180-7A1A-40C7-B28F-EA46314A6E5B-GENID-1-2-1-9-1-5-1-4-1" xml:lang="en"><title>Synchronous
+Requests</title><shortdesc>This document describes the use of synchronous requests by device
+drivers.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
+<section id="GUID-6C508A3B-B2E6-4D16-9421-03EE1A0B595F-GENID-1-2-1-9-1-5-1-4-1-3-1">       <title><b>Synchronous
+requests</b></title>       <p>Synchronous requests are typically used to set
+or retrieve some information for the device driver. These requests almost
+never need to access the hardware itself, and usually complete relatively
+quickly. They return only after the completion of the request and the user
+side thread is blocked till completion. Synchronous requests are usuallly
+initiated by a call to <xref href="GUID-6FBFA078-8253-3E24-B1F8-5F75E86C3066.dita#GUID-6FBFA078-8253-3E24-B1F8-5F75E86C3066/GUID-D774DE92-6431-374A-A1F6-1C7045BD4FE5"><apiname>RBusLogicalChannel::DoControl()</apiname></xref>.
+The request is most likely to be executed in the context of the client user-side
+thread.</p> <p>A driver lists its available synchronous requests
+in an enumeration, for example: </p> <codeblock id="GUID-09E42EC9-CF71-59C0-876E-0651F27E591F-GENID-1-2-1-9-1-5-1-4-1-3-1-4" xml:space="preserve">// Synchronous control messages used with DoControl()
+enum TControl 
+    {
+    EControlConfigure, // Configure the device (UART)
+    EControlTransmitData, // Transmit data over the device (UART)    
+    EControlReceiveData,    // Receive the data from the device 
+    ENumRequests, // Number of synchronous control requests
+    AllRequests = (1&lt;&lt;ENumRequests)-1
+    };</codeblock>     </section>
+<section id="GUID-EC33A9C8-CE41-4937-8008-35502C290581-GENID-1-2-1-9-1-5-1-4-1-3-2"><title>Implementation</title><p>Drivers
+generally implement the <xref href="GUID-06C73075-6095-3D8F-AFC9-FD832958A49C.dita"><apiname>DoControl()</apiname></xref> function in the LDD
+to handle the received synchronous messages. The implementation reads the
+request type and other passed arguments, and handles the request appropriately.
+For example, the following handles <codeph>RExDriver::EControlConfigure</codeph> requests: </p> <codeblock id="GUID-1996BA3A-A895-58C8-B394-4219510DF6D3-GENID-1-2-1-9-1-5-1-4-1-3-2-3" xml:space="preserve">TInt DExDriverLogicalChannel::DoControl(TInt aFunction, TAny* a1, TAny* /*a2*/)
+    {
+    switch (aFunction)
+        {
+        case RExDriver::EControlConfigure:
+            memclr(&amp;c, sizeof(c)));
+            TPtr8 cfg((TUint8*)&amp;c, 0, sizeof(c)));
+            r = Kern::ThreadDesRead(iClient,a1,cfg,0,0);
+            if (r==KErrNone)
+                Pdd()-&gt;Configure(&amp;c);
+            break;
+            ...
+        default:
+                r = KErrNotSupported;
+        }
+    return r;
+    }</codeblock></section>
+</conbody></concept>
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