<?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-9C05C157-D58E-4C43-87E4-82B4F310AEA9" xml:lang="en"><title>DmaChannelMgr Implementation</title><shortdesc>Describes how to write the hardware-specific functions

of the <codeph>DmaChannelMgr</codeph> class.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>The <xref href="GUID-176B8E0D-0422-341B-A134-7C85432E1303.dita"><apiname>DmaChannelMgr</apiname></xref> class is already defined in

the DMA header file but it belongs to the PSL implementation: opening

and closing channels require hardware-specific operations. </p>

<p>When implementing the PSL, you need to provide at least one function:<codeblock xml:space="preserve">TDmaChannel* DmaChannelMgr::Open(TUint32 aOpenId)</codeblock></p>

<p>This function opens a DMA channel and returns the object controlling

this channel.</p>

<p>How the channel is allocated is hardware-dependent. The call to

the <codeph>Open()</codeph> function specifies which channel to open

through the <codeph>aOpenId</codeph> parameter. The format of the

parameter is not part of the DMA platform service and depends on an

agreement between the PSL implementation and the driver using DMA.

The example section below shows a static method, but the allocation

could also be completely or partially dynamic. </p>

<p>If you want to perform a hardware-specific operation when closing

the channel, you also need to update <xref href="GUID-176B8E0D-0422-341B-A134-7C85432E1303.dita#GUID-176B8E0D-0422-341B-A134-7C85432E1303/GUID-909D795A-7303-3A76-9C8E-3B07A97DD716"><apiname>DmaChannelMgr::Close()</apiname></xref>. It is usually not necessary: in the template source code, it is

implemented as doing nothing.</p>

<p/>

<example><title>Open() example</title><p>This example illustrates

a simple allocation scheme where <codeph>aOpenId</codeph> represents

the index of the requested channel in the channel array (<codeph>Controller.iChannels</codeph>).<codeblock xml:space="preserve">

TDmaChannel* DmaChannelMgr::Open(TUint32 aOpenId)

	{

	__DMA_ASSERTA(aOpenId < static_cast<TUint32>(KChannelCount));

	TDmaChannel* pC = Controller.iChannels + aOpenId;

	if (pC->IsOpened())

		pC = NULL;

	else

		{

		pC->iController = &Controller;

		pC->iPslId = aOpenId;

		}

      return pC;

}</codeblock></p></example>

</conbody><related-links>

<link href="GUID-D5ED62EB-744D-42EB-B8CF-D5623BDA5B38.dita"><linktext>DMA

Client Interface Guide</linktext></link>

</related-links></concept>