Synchronization of the IRP of the Windows Driver Development technology detailed

• Synchronous asynchronous operation of the application on the device:

Most of the IRP is initiated by the application's Win32 API function. These Win32 APIs natively support both synchronous and asynchronous operations. For example, ReadFile, WriteFile, and DeviceIoControl, and so on, have both asynchronous and synchronous modes of operation. Synchronous operation of DeviceIoControl:

when synchronizing, the DeviceIoControl internal calls the WaitForSingleObject function to wait for an event. This event is not triggered until the end of the IRP. If you disassemble the IoCompleteRequest kernel function, you will find that the event is set inside the iocompleterequest. DeviceIoControl will temporarily go to sleep until the IRP ends .

For asynchronous operations, the process is:

in the case of an asynchronous operation, when DeviceIoControl is called, an IRP is generated internally, and the IRP is passed to the driver's internal dispatch function. At this point, however, DeviceIoControl does not wait for the IRP to end, but returns directly. When an IRP is terminated over a period of time, the operating system starts an IRP-related event. This event notifies the application that an IRP request has been executed .

Synchronous Operating Devices :

The function declarations of CreateFile are as follows:

1 HANDLE WINAPI CreateFile (2 _in_ lpctstr lpFileName,3 _in_ DWORD dwdesiredaccess,4 _in_ DWORD dwShareMode,5 _in_opt_ lpsecurity_attributes lpsecurityattributes,6 _in_ DWORD dwcreationdisposition,7  _in_ DWORD dwflagsandattributes,8 _in_opt_ HANDLE hTemplateFile9);

The sixth parameter in CreateFile dwFlagsAndAttributes is the key to synchronous asynchronous operations. If file_flag_overlapped is not set in this parameter, subsequent operations on the device are synchronous operations, otherwise all operations are asynchronous operations .

Asynchronous Operation device mode one :

First look at the structure of the overlapped:

The last parameter, hevent, is used to notify the application when the operation is complete.

Synchronization of the IRP of the Windows Driver Development technology detailed