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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&amp; 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&amp; aInfo);
    };


class DOmapMMCStack : public DCardStack
    {
public:
    virtual void GetInterface(TInterfaceId aInterfaceId, MInterface*&amp; 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*&amp; aInterfacePtr)
    {
    if (aInterfaceId == KInterfaceDemandPagingInfo)
        aInterfacePtr = (DMMCStack::MInterface*) iDemandPagingInfo;    
    // etc…
    }

TInt DDemandPagingInfo::DemandPagingInfo(DMMCStack::TDemandPagingInfo&amp; 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>
</conbody></concept>