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<!DOCTYPE concept
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<concept id="GUID-0E93319A-439E-49D8-BF38-C809FEE4BB74" xml:lang="en"><title>User-side
Creation</title><shortdesc>This document describes user-side creation of asynchronous requests.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>Asynchronous requests are commonly initiated by a call to <xref href="GUID-6FBFA078-8253-3E24-B1F8-5F75E86C3066.dita#GUID-6FBFA078-8253-3E24-B1F8-5F75E86C3066/GUID-FCC4A3A9-69F5-3947-8D0F-2AD12086F1E2"><apiname>RBusLogicalChannel::DoRequest()</apiname></xref>.
The user making an asynchronous request creates a <xref href="GUID-E0B34F3E-D4C4-3232-B8B1-7DB35B454646.dita"><apiname>TRequestStatus</apiname></xref> object
and passes it along with the request type to the <xref href="GUID-9D910016-5611-30DD-A139-EE46705A4912.dita"><apiname>DoRequest()</apiname></xref> call.
The request status is changed to <xref href="GUID-B0778F54-C5DD-3307-A1E2-0DD339C4E4E7.dita"><apiname>KRequestPending</apiname></xref> by the
Kernel before sending the message to the driver. The user may then either
wait on the request using <xref href="GUID-C197C9A7-EA05-3F24-9854-542E984C612D.dita#GUID-C197C9A7-EA05-3F24-9854-542E984C612D/GUID-50223158-D05D-33FE-A3DD-FFA9E2F464FF"><apiname>User::WaitForRequest()</apiname></xref>, or it
may queue one or more requests and then wait. It may have an active object
handler to receive the request complete notifications. </p>
<codeblock id="GUID-39AC44C2-1FDF-5A6C-81F0-0BA9BB23DF91" xml:space="preserve">// Request status object for transmit. This object will be used to 
// read the status of asynchronous requests after the notification of 
// request completion
//
 TRequestStatus txStatus;
     
// Call the LDD interface TransmitData() API with test data descriptor 
// and TRequestStatus object as parameters. Here TransmitData() is a
// wrapper over a DoRequest() call.
//
r = ldd.TransmitData(txStatus, KTestSendData);
test(r==KErrNone);
            
// Wait till the request is complete on txStatus. The user thread is 
// blocked with this call, till it is notified about the request 
// completion.
//
User::WaitForRequest(txStatus);
     
// txStatus holds the request completion. TRequestStatus::Int() 
// returns the completion code. It will be KErrNone in case of 
// successful completion.
//
r = txStatus.Int();
test(r==KErrNone);</codeblock>
</conbody></concept>