Отправка пакета URB для ИЗОХРОННОЙ передачи в коде драйвера

#pragma PAGEDCODE
 
NTSTATUS DispatchReadWrite(PDEVICE_OBJECT fdo, PIRP Irp)
    {                           // DispatchReadWrite
    PAGED_CODE();
    PDEVICE_EXTENSION pdx = (PDEVICE_EXTENSION) fdo->DeviceExtension;
    
 
ULONG length=64;
    ULONG packsize = 64;        // known because we write the firmware
    ULONG segsize = 64;//USBD_DEFAULT_MAXIMUM_TRANSFER_SIZE; // default we left in place
    if (segsize / packsize > 255)
        segsize = 255 * packsize;   // maximum based on # packets allowed
    ULONG numirps = (length + segsize - 1) / segsize;
 
 
        PIRP subirp = IoAllocateIrp(64, FALSE);
    
        if (segsize > length)
            segsize = length;   // last transfer is short
 
        ULONG npackets = (segsize + packsize - 1) / packsize; // # packets needed in this stage
        ASSERT(npackets <= 255);    // else we didn't calculate segsize correctly
        ULONG size = GET_ISO_URB_SIZE(npackets); // size of URB needed for that many packets
        PURB urb = (PURB) ExAllocatePool(NonPagedPool, size);
    
    
        RtlZeroMemory(urb, size);
        urb->UrbIsochronousTransfer.Hdr.Length = (USHORT) size;
        urb->UrbIsochronousTransfer.Hdr.Function = URB_FUNCTION_ISOCH_TRANSFER;
        urb->UrbIsochronousTransfer.PipeHandle = pdx->hpipe1;
        urb->UrbIsochronousTransfer.TransferFlags = USBD_TRANSFER_DIRECTION_IN | USBD_SHORT_TRANSFER_OK;
        urb->UrbIsochronousTransfer.TransferBufferLength = segsize;
        urb->UrbIsochronousTransfer.TransferBufferMDL = Irp->MdlAddress;
        urb->UrbIsochronousTransfer.TransferBuffer =     Irp->AssociatedIrp.SystemBuffer;
        urb->UrbIsochronousTransfer.NumberOfPackets = npackets;
        urb->UrbIsochronousTransfer.StartFrame =0;
 
 
        ULONG offset = 0;           // packet offset within subsidiary MDL
 
    
            urb->UrbIsochronousTransfer.IsoPacket[0].Offset = offset;
            
            urb->UrbIsochronousTransfer.IsoPacket[0].Length = 64;
 
        
 
        IoSetNextIrpStackLocation(subirp);
        PIO_STACK_LOCATION stack = IoGetCurrentIrpStackLocation(subirp);
        stack->DeviceObject = fdo;
        stack->Parameters.Others.Argument1 = (PVOID) urb;
        stack->Parameters.Others.Argument2 =  Irp->AssociatedIrp.SystemBuffer;
 
        stack = IoGetNextIrpStackLocation(subirp);
        stack->MajorFunction = IRP_MJ_INTERNAL_DEVICE_CONTROL;
        stack->Parameters.Others.Argument1 = (PVOID) urb;
        stack->Parameters.DeviceIoControl.IoControlCode = IOCTL_INTERNAL_USB_SUBMIT_URB;
        
 
 
        IoCallDriver(pdx->LowerDeviceObject, subirp);
            KdPrint((DRIVERNAME " -     IoCallDriver failed\n"));
 
 
 
    return STATUS_PENDING;
    }                           // DispatchRead