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<concept id="GUID-90B5FDD9-7D59-5035-BF53-2B177655DCD6" xml:lang="en"><title>Migration

Tutorial: Demand Paging and Internal MMC Cards</title><shortdesc>Explains how to change the MMC media driver for when demand paging

is used.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>Demand paging is a change made from Symbian platform v9.3 to how the Kernel

uses RAM and storage media. This topic </p>

<p>For general information on migrating media drivers, see <xref href="GUID-EB2566BD-8F65-5A81-B215-E8B05CFE21C3.dita">Migration

Tutorial: Demand Paging and Media Drivers</xref>. </p>

<section id="GUID-D99E59FE-2515-49F5-9C55-580D1F2AD6A8"><title>PSL changes</title> <p>ROM and code paging can be enabled

for a Multi Media Card (MMC) provided the card is non-removable. Removing

a card would result in a kernel fault whenever the next page-in request is

issued. </p> <p>As the MMC media driver is entirely generic, a way of returning

the paging related information contained in <i>variantmedia.def</i> to the

generic part of the MMC stack is required. This is achieved by modifying the

Platform Specific Layer (PSL) of the MMC stack to implement the <xref href="GUID-B5193656-9819-3E00-A335-EEF1726115A5.dita#GUID-B5193656-9819-3E00-A335-EEF1726115A5/GUID-7DAC0CF1-4AFE-3F68-8488-632535783A80"><apiname>DMMCStack::MDemandPagingInfo</apiname></xref> interface

method: </p> <codeblock id="GUID-7B1FA673-641B-54C7-BC6B-DCDBE25297B8" xml:space="preserve">class DMMCStack : public Dbase

    {

public:

    // etc…

    };

/** 

Demand paging support 

@see KInterfaceDemandPagingInfo

*/

class TDemandPagingInfo

    {

public:

    const TInt* iPagingDriveList;

    TInt  iDriveCount;

    TUint iPagingType;

    TInt  iReadShift;

    TUint iNumPages;

    TBool iWriteProtected;

    TUint iSpare[3];

    };

class MDemandPagingInfo

    {

public:

    virtual TInt DemandPagingInfo(TDemandPagingInfo& aInfo) = 0;

    // etc…

    };</codeblock> <p>This example is taken from the H4 HRP <i>VariantMedia.def</i> changes: </p> <codeblock id="GUID-DD8297C4-6033-5AB1-838C-F0DFE1C7C749" xml:space="preserve">// Variant parameters for the MMC Controller (EPBUSMMC.DLL)

#define MMC_DRIVECOUNT 1

#define MMC_DRIVELIST 1

#define MMC_NUMMEDIA 1

#define MMC_DRIVENAME "MultiMediaCard0" 

#define MMC_PAGING_TYPE    DPagingDevice::ERom | DPagingDevice::ECode

#define MMC_PAGEDRIVELIST    1            // code paging from User Data

#define    MMC_PAGEDRIVECOUNT     1

#define MMC_NUM_PAGES        8</codeblock> <p>This example is from H4 MMC

stack class definition: </p> <codeblock id="GUID-FC2E902E-E98C-5E0E-9337-D3D5BB14FBB6" xml:space="preserve">class DDemandPagingInfo : public DMMCStack::MDemandPagingInfo

    {

public:

    virtual TInt DemandPagingInfo(DMMCStack::TDemandPagingInfo& aInfo);

    };

class DOmapMMCStack : public DCardStack

    {

public:

    virtual void GetInterface(TInterfaceId aInterfaceId, MInterface*& aInterfacePtr);

    // etc…

private:

    DDemandPagingInfo* iDemandPagingInfo;

    // etc…

    };</codeblock> <p>This example is from H4 MMC stack class implementation: </p> <codeblock id="GUID-824160DE-295D-5BA2-B2BE-A5590301B9EA" xml:space="preserve">TInt DOmapMMCStack::Init()

    {

    if((iDemandPagingInfo = new DDemandPagingInfo()) == NULL)

        return KErrNoMemory;

    // etc…

    }

void DOmapMMCStack::GetInterface(TInterfaceId aInterfaceId, MInterface*& aInterfacePtr)

    {

    if (aInterfaceId == KInterfaceDemandPagingInfo)

        aInterfacePtr = (DMMCStack::MInterface*) iDemandPagingInfo;    

    // etc…

    }

TInt DDemandPagingInfo::DemandPagingInfo(DMMCStack::TDemandPagingInfo& aDemandPagingInfo)    

    {

    static const TInt pagingDriveNumbers[MMC_PAGEDRIVECOUNT] = {MMC_PAGEDRIVELIST};

    aDemandPagingInfo.iPagingDriveList = pagingDriveNumbers;

    aDemandPagingInfo.iDriveCount = MMC_PAGEDRIVECOUNT;

    aDemandPagingInfo.iPagingType = MMC_PAGING_TYPE;

    aDemandPagingInfo.iReadShift = 9;

    aDemandPagingInfo.iNumPages = MMC_NUM_PAGES;

    return KErrNone;

    }</codeblock> </section>

<section id="GUID-6389CCE7-339D-4F41-B875-4636C5993C6C"><title>Preparing an internal MMC card for ROM paging - MMCLoader</title> <p>To

support ROM paging from an internal card, the MMCLoader utility is used to

write the ROM image to the card. MMCLoader can be found in <filepath>e32utils/mmcloader</filepath>. </p> <p>The

paged image is written as a normal file under the FAT file system. For paging

to work however, the images file’s clusters must all be contiguous so, before

doing anything else, MMCLoader formats the card. It then writes the paged

part of the ROM to a file and checks that the file’s clusters are contiguous,

which is normally the case as the card has just been formatted. A pointer

to the image file is stored in the boot sector. When the board is rebooted

the MMC/SD media driver reads the boot sector and uses this pointer to determine

where the image file starts so that it can begin to satisfy paging requests. </p> <p>MMCLoader

takes the filename of the original ROM image file as an input. It then splits

the given file into unpaged and paged files. The following code fragment shows

the syntax: </p> <codeblock id="GUID-0CFE9814-4FEA-5FF1-9027-82E207596C68" xml:space="preserve">Syntax: mmcloader &lt;RomSrcFileName&gt; &lt;UnPagedRomDstFileName&gt; &lt;PagedRomDstFileName&gt;

Eg:     mmcloader z:\\core.img d:\\sys$rom.bin d:\\sys$rom.pag</codeblock> </section>