Kernel Mode Driver Framework >> C/C++ (PNP) >> Timer

DPC

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參考資訊：
1. Source Code

由於I/O Timer的Timer間隔固定為一秒，如果使用者想要可以彈性設定的Timer間隔，則需要使用DPC Timer，使用的步驟：
1. KeInitializeTimer()
2. KeInitializeDpc()
3. KeSetTimer()
4. KeCancelTimer()

DPC Timer如果使用KeSetTimer()做設定時，其Timer為一次性，也就是Callback僅會被呼叫一次，如果要使用週期性Timer，則需要改用KeSetTimerEx()，KeSetTimerEx()宣告如下：

BOOLEAN KeSetTimerEx(PKTIMER Timer, LARGE_INTEGER DueTime, LONG Period, PKDPC Dpc);

DueTime是第一次Timer的間隔，之後的間隔則使用Period數值。

main.c

#include <ntddk.h>
#include <wdf.h>

#define DEV_NAME L"\\Device\\MyDriver"
#define SYM_NAME L"\\DosDevices\\MyDriver"

#define IOCTL_START CTL_CODE(FILE_DEVICE_UNKNOWN, 0x800, METHOD_BUFFERED, FILE_ANY_ACCESS)
#define IOCTL_STOP  CTL_CODE(FILE_DEVICE_UNKNOWN, 0x801, METHOD_BUFFERED, FILE_ANY_ACCESS)

KDPC dpc;
KTIMER obj;
ULONG cnt=0;
PDEVICE_OBJECT pDevice;

VOID OnTimer(struct _KDPC *Dpc, PVOID DeferredContext, PVOID SystemArgument1, PVOID SystemArgument2)
{
  cnt+= 1;
  DbgPrint("DpcTimer: %d\n", cnt);
}
 
void IrpFileCreate(WDFDEVICE Device, WDFREQUEST Request, WDFFILEOBJECT FileObject)
{  
  DbgPrint("IrpFieCreate");
  WdfRequestComplete(Request, STATUS_SUCCESS);
}

void IrpFileClose(WDFFILEOBJECT FileObject)
{
  DbgPrint("IrpFieClose");
}

void IrpIOCTL(WDFQUEUE Queue, WDFREQUEST Request, size_t OutputBufferLength, size_t InputBufferLength, ULONG IoControlCode)
{
  LARGE_INTEGER tt;
  
  switch(IoControlCode){
  case IOCTL_START:
    DbgPrint("IOCTL_START");
    cnt = 0;
    tt.HighPart|= -1;
    tt.LowPart = (ULONG)-10000000;
    KeSetTimerEx(&obj, tt, 1000, &dpc);
    break;
  case IOCTL_STOP:
    DbgPrint("IOCTL_STOP");
    KeCancelTimer(&obj);
    break;
  }
  WdfRequestComplete(Request, STATUS_SUCCESS);
}

NTSTATUS AddDevice(WDFDRIVER Driver, PWDFDEVICE_INIT pDeviceInit)
{
  WDFDEVICE device;
  UNICODE_STRING suDevName;
  UNICODE_STRING szSymName;
  WDF_FILEOBJECT_CONFIG file_cfg;
  WDF_IO_QUEUE_CONFIG ioqueue_cfg;
  
  RtlInitUnicodeString(&suDevName, DEV_NAME);
  RtlInitUnicodeString(&szSymName, SYM_NAME);
  WdfDeviceInitAssignName(pDeviceInit, &suDevName);
  
  WdfDeviceInitSetIoType(pDeviceInit, WdfDeviceIoBuffered);
  WDF_FILEOBJECT_CONFIG_INIT(&file_cfg, IrpFileCreate, IrpFileClose, NULL);
  WdfDeviceInitSetFileObjectConfig(pDeviceInit, &file_cfg, WDF_NO_OBJECT_ATTRIBUTES);
  WdfDeviceCreate(&pDeviceInit, WDF_NO_OBJECT_ATTRIBUTES, &device);
  WdfDeviceCreateSymbolicLink(device, &szSymName);
  
  pDevice = WdfDeviceWdmGetDeviceObject(device);
  KeInitializeTimer(&obj);
  KeInitializeDpc(&dpc, OnTimer, pDevice);
  WDF_IO_QUEUE_CONFIG_INIT_DEFAULT_QUEUE(&ioqueue_cfg, WdfIoQueueDispatchSequential);
  ioqueue_cfg.EvtIoDeviceControl = IrpIOCTL;
  return WdfIoQueueCreate(device, &ioqueue_cfg, WDF_NO_OBJECT_ATTRIBUTES, WDF_NO_HANDLE);
}

NTSTATUS DriverEntry(PDRIVER_OBJECT pOurDriver, PUNICODE_STRING pRegistry)
{
  WDF_DRIVER_CONFIG config;

  WDF_DRIVER_CONFIG_INIT(&config, AddDevice);
  return WdfDriverCreate(pOurDriver, pRegistry, WDF_NO_OBJECT_ATTRIBUTES, &config, WDF_NO_HANDLE);
}

AddDevice()初始化Timer以及DPC Object
IrpIOCTL()啟動或停止DPC Timer
OnTimer()僅列印訊息，其餘事情不做

app.c

#define INITGUID
#include <windows.h>
#include <winioctl.h>
#include <strsafe.h>
#include <setupapi.h>
#include <stdio.h>
#include <stdlib.h>

#define IOCTL_START CTL_CODE(FILE_DEVICE_UNKNOWN, 0x800, METHOD_BUFFERED, FILE_ANY_ACCESS)
#define IOCTL_STOP  CTL_CODE(FILE_DEVICE_UNKNOWN, 0x801, METHOD_BUFFERED, FILE_ANY_ACCESS)

int __cdecl main(int argc, char* argv[])
{
  HANDLE hFile = NULL;
  DWORD dwRet = 0;

  hFile = CreateFile("\\\\.\\MyDriver", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);
  if (hFile == INVALID_HANDLE_VALUE) {
    printf("failed to open mydriver\n");
    return -1;
  }
  DeviceIoControl(hFile, IOCTL_START, NULL, 0, NULL, 0, &dwRet, NULL);
  Sleep(3000);
  DeviceIoControl(hFile, IOCTL_STOP, NULL, 0, NULL, 0, &dwRet, NULL);
  CloseHandle(hFile);
  return 0;
}

結果

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