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<!DOCTYPE concept

  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

<concept id="GUID-30978E00-D244-44CD-8F4E-9676DF172A52" xml:lang="en"><title>Driver-side

Handling</title><shortdesc>This document describes how device drivers handle asynchronous

requests.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>Drivers generally implement the <xref href="GUID-9D910016-5611-30DD-A139-EE46705A4912.dita"><apiname>DoRequest()</apiname></xref> function

in the LDD to handle the received asynchronous messages. </p>

<p>The implementation reads the request type and other passed arguments, and

initiates handling of the request appropriately. </p>

<p>The return value of this function only indicates the status of the message

reception to the driver. It does not actually indicate the request completion

result. </p>

<codeblock id="GUID-335BB3F8-7B2B-5FC4-A8D1-204E6B24FECD" xml:space="preserve">TInt DExDriverLogicalChannel::DoRequest(TInt aReqNo, TRequestStatus* aStatus,

        TAny* a1, TAny* a2)

    {

    switch (aReqNo)

        {

        case RExDriverChannel::ERequestTransmitData:

            // Call TransmitData function

            r = TransmitData ((const TDesC8*)a1);

            // The status object is stored 

            // to be used when notifying the completion of the 

            // request at a later point.

            //

            iTxDataStatus = aStatus;

            break;

        }

    return r;

    }</codeblock>