VOID NTAPI ScsiClassBuildRequest	(	PDEVICE_OBJECT	DeviceObject,
		PIRP	Irp
	)
Definition at line 3219 of file class2.c.
Referenced by ScsiCdRomStartIo(), ScsiClassReadWrite(), and ScsiClassSplitRequest().
{
    PDEVICE_EXTENSION   deviceExtension = DeviceObject->DeviceExtension;
    PIO_STACK_LOCATION  currentIrpStack = IoGetCurrentIrpStackLocation(Irp);
    PIO_STACK_LOCATION  nextIrpStack = IoGetNextIrpStackLocation(Irp);
    LARGE_INTEGER       startingOffset = currentIrpStack->Parameters.Read.ByteOffset;
    PSCSI_REQUEST_BLOCK srb;
    PCDB                cdb;
    ULONG               logicalBlockAddress;
    USHORT              transferBlocks;

    //
    // Calculate relative sector address.
    //

    logicalBlockAddress =  (ULONG)(Int64ShrlMod32(startingOffset.QuadPart, deviceExtension->SectorShift));

    //
    // Allocate an Srb.
    //

    srb = ExAllocateFromNPagedLookasideList(&deviceExtension->SrbLookasideListHead);

    srb->SrbFlags = 0;

    //
    // Write length to SRB.
    //

    srb->Length = SCSI_REQUEST_BLOCK_SIZE;

    //
    // Set up IRP Address.
    //

    srb->OriginalRequest = Irp;

    //
    // Set up target ID and logical unit number.
    //

    srb->PathId = deviceExtension->PathId;
    srb->TargetId = deviceExtension->TargetId;
    srb->Lun = deviceExtension->Lun;
    srb->Function = SRB_FUNCTION_EXECUTE_SCSI;
    srb->DataBuffer = MmGetMdlVirtualAddress(Irp->MdlAddress);

    //
    // Save byte count of transfer in SRB Extension.
    //

    srb->DataTransferLength = currentIrpStack->Parameters.Read.Length;

    //
    // Initialize the queue actions field.
    //

    srb->QueueAction = SRB_SIMPLE_TAG_REQUEST;

    //
    // Queue sort key is Relative Block Address.
    //

    srb->QueueSortKey = logicalBlockAddress;

    //
    // Indicate auto request sense by specifying buffer and size.
    //

    srb->SenseInfoBuffer = deviceExtension->SenseData;
    srb->SenseInfoBufferLength = SENSE_BUFFER_SIZE;

    //
    // Set timeout value of one unit per 64k bytes of data.
    //

    srb->TimeOutValue = ((srb->DataTransferLength + 0xFFFF) >> 16) *
                        deviceExtension->TimeOutValue;

    //
    // Zero statuses.
    //

    srb->SrbStatus = srb->ScsiStatus = 0;
    srb->NextSrb = 0;

    //
    // Indicate that 10-byte CDB's will be used.
    //

    srb->CdbLength = 10;

    //
    // Fill in CDB fields.
    //

    cdb = (PCDB)srb->Cdb;

    //
    // Zero 12 bytes for Atapi Packets
    //

    RtlZeroMemory(cdb, MAXIMUM_CDB_SIZE);

    cdb->CDB10.LogicalUnitNumber = deviceExtension->Lun;
    transferBlocks = (USHORT)(currentIrpStack->Parameters.Read.Length >> deviceExtension->SectorShift);

    //
    // Move little endian values into CDB in big endian format.
    //

    cdb->CDB10.LogicalBlockByte0 = ((PFOUR_BYTE)&logicalBlockAddress)->Byte3;
    cdb->CDB10.LogicalBlockByte1 = ((PFOUR_BYTE)&logicalBlockAddress)->Byte2;
    cdb->CDB10.LogicalBlockByte2 = ((PFOUR_BYTE)&logicalBlockAddress)->Byte1;
    cdb->CDB10.LogicalBlockByte3 = ((PFOUR_BYTE)&logicalBlockAddress)->Byte0;

    cdb->CDB10.TransferBlocksMsb = ((PFOUR_BYTE)&transferBlocks)->Byte1;
    cdb->CDB10.TransferBlocksLsb = ((PFOUR_BYTE)&transferBlocks)->Byte0;

    //
    // Set transfer direction flag and Cdb command.
    //

    if (currentIrpStack->MajorFunction == IRP_MJ_READ) {

        DebugPrint((3, "ScsiClassBuildRequest: Read Command\n"));

        srb->SrbFlags |= SRB_FLAGS_DATA_IN;
        cdb->CDB10.OperationCode = SCSIOP_READ;

    } else {

        DebugPrint((3, "ScsiClassBuildRequest: Write Command\n"));

        srb->SrbFlags |= SRB_FLAGS_DATA_OUT;
        cdb->CDB10.OperationCode = SCSIOP_WRITE;
    }

    //
    // If this is not a write-through request, then allow caching.
    //

    if (!(currentIrpStack->Flags & SL_WRITE_THROUGH)) {

        srb->SrbFlags |= SRB_FLAGS_ADAPTER_CACHE_ENABLE;

    } else {

        //
        // If write caching is enable then force media access in the
        // cdb.
        //

        if (deviceExtension->DeviceFlags & DEV_WRITE_CACHE) {
            cdb->CDB10.ForceUnitAccess = TRUE;
        }
    }

    //
    // Or in the default flags from the device object.
    //

    srb->SrbFlags |= deviceExtension->SrbFlags;

    //
    // Set up major SCSI function.
    //

    nextIrpStack->MajorFunction = IRP_MJ_SCSI;

    //
    // Save SRB address in next stack for port driver.
    //

    nextIrpStack->Parameters.Scsi.Srb = srb;

    //
    // Save retry count in current IRP stack.
    //

    currentIrpStack->Parameters.Others.Argument4 = (PVOID)MAXIMUM_RETRIES;

    //
    // Set up IoCompletion routine address.
    //

    IoSetCompletionRoutine(Irp, ScsiClassIoComplete, srb, TRUE, TRUE, TRUE);

    return;

} // end ScsiClassBuildRequest()
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