#001   //该函数实现对发送URB到USB物理总线驱动
#002   NTSTATUS
#003   CallUSBD(
#004       IN PDEVICE_OBJECT DeviceObject,
#005       IN PURB           Urb
#006       )
#007   {
#008       PIRP               irp;
#009       KEVENT             event;
#010       NTSTATUS           ntStatus;
#011       IO_STATUS_BLOCK    ioStatus;
#012       PIO_STACK_LOCATION nextStack;
#013       PDEVICE_EXTENSION  deviceExtension;
#014   
#015    //首先是变量初始化
#016       irp = NULL;
#017       deviceExtension = DeviceObject->DeviceExtension;
#018       //初始化事件
#019       KeInitializeEvent(&event, NotificationEvent, FALSE);
#020    //创建IO控制码相关的IRP
#021       irp = IoBuildDeviceIoControlRequest
(IOCTL_INTERNAL_USB_SUBMIT_URB, 
#022                                           deviceExtension->
TopOfStackDeviceObject,
#023                                           NULL, 
#024                                           0, 
#025                                           NULL, 
#026                                           0, 
#027                                           TRUE, 
#028                                           &event, 
#029                                           &ioStatus);
#030   
#031       if(!irp) {
#032     //如果IRP创建失败则返回
#033           BulkUsb_DbgPrint(1, ("IoBuildDeviceIo
ControlRequest failed\n"));
#034           return STATUS_INSUFFICIENT_RESOURCES;
#035       }
#036    //得到下一层设备栈
#037       nextStack = IoGetNextIrpStackLocation(irp);
#038       ASSERT(nextStack != NULL);
#039       nextStack->Parameters.Others.Argument1 = Urb;
#040       BulkUsb_DbgPrint(3, ("CallUSBD::"));
#041       BulkUsb_IoIncrement(deviceExtension);
#042    //通过IoCallDriver将IRP发送到底层驱动
#043       ntStatus = IoCallDriver(deviceExtension->
TopOfStackDeviceObject, irp);
#044    //如果IRP是异步完成时，等待其结束
#045       if(ntStatus == STATUS_PENDING) {
#046     //等待IRP结束
#047           KeWaitForSingleObject(&event, 
#048                                 Executive, 
#049                                 KernelMode, 
#050                                 FALSE, 
#051                                 NULL);
#052           ntStatus = ioStatus.Status;
#053       }
#054       //调用结束
#055       BulkUsb_DbgPrint(3, ("CallUSBD::"));
#056       BulkUsb_IoDecrement(deviceExtension);
#057       return ntStatus;
#058   }