Migration +Tutorial: Demand Paging and Internal MMC Cards

Demand paging is a change made from Symbian platform v9.3 to how the Kernel +uses RAM and storage media. This topic

For general information on migrating media drivers, see Migration +Tutorial: Demand Paging and Media Drivers.

PSL changes

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.

As the MMC media driver is entirely generic, a way of returning +the paging related information contained in variantmedia.def 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 DMMCStack::MDemandPagingInfo interface +method:

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… + };

This example is taken from the H4 HRP VariantMedia.def changes:

// 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

This example is from H4 MMC +stack class definition:

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… + };

This example is from H4 MMC stack class implementation:

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; + }

Preparing an internal MMC card for ROM paging - MMCLoader

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 e32utils/mmcloader.

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.

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:

Syntax: mmcloader <RomSrcFileName> <UnPagedRomDstFileName> <PagedRomDstFileName> +Eg: mmcloader z:\\core.img d:\\sys$rom.bin d:\\sys$rom.pag