文章标题

在《》我们所说的读写操作在本篇实现。
在WDF中实现此功能主要为：EvtIoRead和EvtIoWrite。

首先，在EvtDeviceAdd设置以上两个回调事件。

 ioQueueConfig.EvtIoRead = EvtIoRead;
 ioQueueConfig.EvtIoWrite = EvtIoWrite;

然后，在EvtDevicePrepareHardware中获取WDFUSBPIPE并测试他。

 pDeviceContext->BulkReadPipe = WdfUsbInterfaceGetConfiguredPipe(
                                                  pDeviceContext->UsbInterface,
                                                  BULK_IN_ENDPOINT_INDEX,
                                                  NULL);// pipeInfo

    WdfUsbTargetPipeSetNoMaximumPacketSizeCheck(pDeviceContext->BulkReadPipe);

    pDeviceContext->BulkWritePipe = WdfUsbInterfaceGetConfiguredPipe(
                                                  pDeviceContext->UsbInterface,
                                                  BULK_OUT_ENDPOINT_INDEX,
                                                  NULL);// pipeInfo

    WdfUsbTargetPipeSetNoMaximumPacketSizeCheck(pDeviceContext->BulkWritePipe);

（1）获取WDFUSBPIPE
    使用[](https://msdn.microsoft.com/en-us/library/windows/hardware/ff550057%28v=vs.85%29.aspx "WdfUsbInterfaceGetConfiguredPipe")方法.

WDFUSBPIPE WdfUsbInterfaceGetConfiguredPipe(
  [in]            WDFUSBINTERFACE           UsbInterface,
  [in]            UCHAR                     PipeIndex,
  [out, optional] PWDF_USB_PIPE_INFORMATION PipeInfo
);

(2) 测试WDFUSBPIPE
    使用[](https://msdn.microsoft.com/en-us/library/windows/hardware/ff550057%28v=vs.85%29.aspx "WdfUsbTargetPipeSetNoMaximumPacketSizeCheck")方法

VOID WdfUsbTargetPipeSetNoMaximumPacketSizeCheck(
  [in] WDFUSBPIPE Pipe
);

最后，实现以上两个回调事件和他们的完成例程。
    1. 获得传输缓存
         读：[](https://msdn.microsoft.com/en-us/library/windows/hardware/ff550019%28v=vs.85%29.aspx "WdfRequestRetrieveOutputMemory")

NTSTATUS WdfRequestRetrieveOutputMemory(
  [in]  WDFREQUEST Request,
  [out] WDFMEMORY  *Memory
);

    写：[](https://msdn.microsoft.com/en-us/library/windows/hardware/ff550015%28v=vs.85%29.aspx "WdfRequestRetrieveInputMemory")

NTSTATUS WdfRequestRetrieveInputMemory(
  [in]  WDFREQUEST Request,
  [out] WDFMEMORY  *Memory
);

    2. 格式化并发送一个请求对象到USB驱动程序堆栈
        读：[](https://msdn.microsoft.com/en-us/library/windows/hardware/ff551136%28v=vs.85%29.aspx "WdfUsbTargetPipeFormatRequestForRead")

NTSTATUS WdfUsbTargetPipeFormatRequestForRead(
  [in]           WDFUSBPIPE        Pipe,
  [in]           WDFREQUEST        Request,
  [in, optional] WDFMEMORY         ReadMemory,
  [in, optional] PWDFMEMORY_OFFSET ReadOffset
);

    写：[](https://msdn.microsoft.com/en-us/library/windows/hardware/ff551141%28v=vs.85%29.aspx "WdfUsbTargetPipeFormatRequestForWrite")

NTSTATUS WdfUsbTargetPipeFormatRequestForWrite(
  [in]           WDFUSBPIPE        Pipe,
  [in]           WDFREQUEST        Request,
  [in, optional] WDFMEMORY         WriteMemory,
  [in, optional] PWDFMEMORY_OFFSET WriteOffset
);

    3. 对请求实现一个完成例程
       (1) 设置完成例程
           使用[](https://msdn.microsoft.com/en-us/library/windows/hardware/ff550030%28v=vs.85%29.aspx "WdfRequestSetCompletionRoutine")方法。

VOID WdfRequestSetCompletionRoutine(
  [in]           WDFREQUEST                         Request,
  [in, optional] PFN_WDF_REQUEST_COMPLETION_ROUTINE CompletionRoutine,
  [in, optional] WDFCONTEXT                         CompletionContext
);

(2) 完成例程
    1). 检查请求状态

status = CompletionParams->IoStatus.Status;

    2). 检查传输的字节数
        读完：

bytesRead =  usbCompletionParams->Parameters.PipeRead.Length;

        写完：

bytesWritten =  usbCompletionParams->Parameters.PipeWrite.Length;

    3). 检查USBD状态
        首先，赋值

usbCompletionParams = CompletionParams->Parameters.Usb.Completion;

        最后，获取

usbCompletionParams->UsbdStatus;

参考文章：
1. 《Working with USB Pipes》
2. 《How to send USB bulk transfer requests》