EVT_WDF_DEVICE_FILE_CREATE callback function

[Applies to KMDF and UMDF]

A driver's EvtDeviceFileCreate callback function handles operations that must be performed when an application requests access to a device.

Syntax

EVT_WDF_DEVICE_FILE_CREATE EvtWdfDeviceFileCreate;

void EvtWdfDeviceFileCreate(
  WDFDEVICE Device,
  WDFREQUEST Request,
  WDFFILEOBJECT FileObject
)
{...}

Parameters

Device

A handle to a framework device object.

Request

A handle to a framework request object that represents a file creation request.

FileObject

A handle to a framework file object that describes a file that is being opened for the specified request. This parameter is NULL if the driver has specified WdfFileObjectNotRequired for the FileObjectClass member of the WDF_FILEOBJECT_CONFIG structure.

Return Value

None

Remarks

The framework calls a driver's EvtDeviceFileCreate callback function when a user application or another driver opens the device to perform an I/O operation, such as reading or writing a file.

The driver can pass the Request handle to WdfRequestGetParameters to retrieve parameters that are associated with the file creation request. The parameters are stored in the Parameters.Create member of the WDF_REQUEST_PARAMETERS structure.

This callback function is called synchronously, in the context of the user thread that opens the device.

To register an EvtDeviceFileCreate callback function, the driver must call the WdfDeviceInitSetFileObjectConfig method.

For more information about framework file objects and the EvtDeviceFileCreate callback function, see Framework File Objects.

Examples

To define an EvtDeviceFileCreate callback function, you must first provide a function declaration that identifies the type of callback function you’re defining. Windows provides a set of callback function types for drivers. Declaring a function using the callback function types helps Code Analysis for Drivers, Static Driver Verifier (SDV), and other verification tools find errors, and it’s a requirement for writing drivers for the Windows operating system.

For example, to define an EvtDeviceFileCreate callback function that is named MyDeviceFileCreate, use the EVT_WDF_DEVICE_FILE_CREATE type as shown in this code example:

EVT_WDF_DEVICE_FILE_CREATE  MyDeviceFileCreate;

Then, implement your callback function as follows:

_Use_decl_annotations_
VOID
 MyDeviceFileCreate (
    WDFDEVICE  Device,
    WDFREQUEST  Request,
    WDFFILEOBJECT  FileObject
    )
  {...}

The EVT_WDF_DEVICE_FILE_CREATE function type is defined in the Wdfdevice.h header file. To more accurately identify errors when you run the code analysis tools, be sure to add the Use_decl_annotations annotation to your function definition. The Use_decl_annotations annotation ensures that the annotations that are applied to the EVT_WDF_DEVICE_FILE_CREATE function type in the header file are used. For more information about the requirements for function declarations, see Declaring Functions by Using Function Role Types for KMDF Drivers. For information about Use_decl_annotations, see Annotating Function Behavior.

Requirements

   
Target Platform Universal
Minimum KMDF version 1.0
Minimum UMDF version 2.0
Header wdfdevice.h (include Wdf.h)
IRQL PASSIVE_LEVEL

See Also

WDF_FILEOBJECT_CONFIG