急!求讲解张帆《Windows驱动开发技术详解》的虚拟串口驱动，求讲解

问题：急!求讲解张帆《Windows驱动开发技术详解》的虚拟串口驱动，求讲解
描述:

驱动开发张帆windows

第19章，虚拟串口驱动，求讲解。有意的加我qq:545039712.我出钱。
需要讲解的代码如下：
NTSTATUS HelloWDMRead(IN PDEVICE_OBJECT fdo,
                        IN PIRP Irp)
{
KdPrint(("HelloWDMRead\n"));
    NTSTATUS ntStatus = STATUS_SUCCESS;// Assume success
PDEVICE_EXTENSION pExtension = (PDEVICE_EXTENSION)fdo->DeviceExtension;
    PIO_STACK_LOCATION irpSp = IoGetCurrentIrpStackLocation( Irp );
ULONG BufLen = irpSp->Parameters.Read.Length;
PCHAR pBuf = (PCHAR)Irp->AssociatedIrp.SystemBuffer;
    KIRQL OldIrql;
    PDRIVER_CANCEL pOldCancelRoutine;
Irp->IoStatus.Information = 0;
DbgPrint("DeviceObject:%08X Read\n",fdo);
if (BufLen == 0)
    {
ntStatus = STATUS_SUCCESS;
    }
else
{
        KeAcquireSpinLock(&pExtension->WriteSpinLock, &OldIrql);
RtlCopyMemory(pBuf,pExtension->Buffer,BufLen);
Irp->IoStatus.Information = BufLen;
if (BufLen==0 && pExtension->pReadIrp==NULL) // nothing, store
{
pExtension->pReadIrp = Irp;
Irp->IoStatus.Status = ntStatus = STATUS_PENDING;
            IoSetCancelRoutine(Irp, DriverCancelCurrentReadIrp);
            if (Irp->Cancel)
            {
                pOldCancelRoutine = IoSetCancelRoutine(Irp, NULL);
                if (pOldCancelRoutine != NULL)
                {
                    // Nein, also IRP hier abbrechen
                    Irp->IoStatus.Status = ntStatus = STATUS_CANCELLED;
                    pExtension->pReadIrp = NULL;
                }
                else
                {
                    // Ja, Cancel-Routine wird Request beenden
                    IoMarkIrpPending(Irp);
                }
}
else
{
                    IoMarkIrpPending(Irp);
}
}
        KeReleaseSpinLock(&pExtension->WriteSpinLock, OldIrql);
}
    Irp->IoStatus.Status = ntStatus;
if (ntStatus != STATUS_PENDING)
IoCompleteRequest( Irp, IO_NO_INCREMENT );
    return ntStatus;
}
NTSTATUS HelloWDMWrite(IN PDEVICE_OBJECT fdo,
                        IN PIRP Irp)
{
KdPrint(("HelloWDMWrite\n"));
    NTSTATUS ntStatus = STATUS_SUCCESS;// Assume success
PDEVICE_EXTENSION pdx = (PDEVICE_EXTENSION)fdo->DeviceExtension;
    PIO_STACK_LOCATION irpSp = IoGetCurrentIrpStackLocation( Irp );
ULONG DataLen = irpSp->Parameters.Write.Length;
PUCHAR pData = (PUCHAR)Irp->AssociatedIrp.SystemBuffer;
    KIRQL OldIrql;
    PIRP            pOldReadIrp = NULL;
    PDRIVER_CANCEL  pOldCancelRoutine;
Irp->IoStatus.Information = 0;
ntStatus = STATUS_SUCCESS;
if (DataLen == 0)
    {
ntStatus = STATUS_SUCCESS;
    }else if (DataLen>COMBUFLEN)
    {
ntStatus = STATUS_INVALID_PARAMETER;
    }
else
{
KdPrint(("Write\n"));
        
KeAcquireSpinLock(&pdx->WriteSpinLock, &OldIrql);
RtlCopyMemory(pdx->Buffer,pData,DataLen);
pdx->uReadWrite = DataLen;
if (pdx->pReadIrp != NULL) // drop it out
{
pOldReadIrp = pdx->pReadIrp;
pOldCancelRoutine = IoSetCancelRoutine(pOldReadIrp, NULL);
if (pOldCancelRoutine != NULL)
{
pOldReadIrp->IoStatus.Information = 0;
pOldReadIrp->IoStatus.Status = STATUS_SUCCESS;
pdx->pReadIrp = NULL;
}
else
{
pOldReadIrp = NULL;
}
}
DriverCheckEvent(pdx, SERIAL_EV_RXCHAR | SERIAL_EV_RX80FULL);
// DriverCheckEvent(pdx, SERIAL_EV_TXEMPTY);
        KeReleaseSpinLock(&pdx->WriteSpinLock, OldIrql);
    if (pOldReadIrp != NULL)
    IoCompleteRequest(pOldReadIrp, IO_NO_INCREMENT);
}
    Irp->IoStatus.Status = ntStatus;
    Irp->IoStatus.Information = DataLen;
    IoCompleteRequest( Irp, IO_NO_INCREMENT );
    return ntStatus;
}

---

解决方案1:

读写的 操作  解释什么呢？ 难道是需要 逐行代码注释？