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WDF_FILEOBJECT_CLASS enumeration (wdfdevice.h)

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[Applies to KMDF and UMDF]

The WDF_FILEOBJECT_CLASS enumeration defines values that identify whether a driver requires a framework file object to represent a file that an application or another driver is attempting to create or open. These values also specify where the framework can store the object's handle.

Syntax

typedef enum _WDF_FILEOBJECT_CLASS {
  WdfFileObjectInvalid = 0,
  WdfFileObjectNotRequired = 1,
  WdfFileObjectWdfCanUseFsContext = 2,
  WdfFileObjectWdfCanUseFsContext2 = 3,
  WdfFileObjectWdfCannotUseFsContexts = 4,
  WdfFileObjectCanBeOptional = 0x80000000
} WDF_FILEOBJECT_CLASS, *PWDF_FILEOBJECT_CLASS;

Constants

 
WdfFileObjectInvalid
Value: 0
Reserved for internal use.
WdfFileObjectNotRequired
Value: 1
The driver does not require a framework file object.
WdfFileObjectWdfCanUseFsContext
Value: 2
The driver requires a framework file object. The framework can store the object's handle in the FsContext member of the file's Windows Driver Model (WDM) FILE_OBJECT structure.
WdfFileObjectWdfCanUseFsContext2
Value: 3
The driver requires a framework file object. The framework can store the object's handle in the FsContext2 member of the file's WDM FILE_OBJECT structure.
WdfFileObjectWdfCannotUseFsContexts
Value: 4
The driver requires a framework file object. The framework cannot store the object's handle in the FsContext or FsContext2 member of the file's WDM FILE_OBJECT structure, because one or more drivers are using these members. Therefore, the framework must store the handle internally.
WdfFileObjectCanBeOptional
Value: 0x80000000
The driver typically requires a framework file object, but the driver can also handle special situations in which a framework file object is missing or different. For more information about these situations, see the following Remarks section.

WdfFileObjectCanBeOptional is a bit flag that your driver can OR with the WdfFileObjectWdfCanUseFsContext, WdfFileObjectWdfCanUseFsContext2, or WdfFileObjectWdfCannotUseFsContexts enumerator value.

Most framework-based drivers do not use this bit flag.

The WdfFileObjectCanBeOptional value is available in version 1.9 and later versions of KMDF.

Remarks

The WDF_FILEOBJECT_CLASS enumeration is used in the WDF_FILEOBJECT_CONFIG structure.

If your driver calls WdfRequestGetFileObject to obtain framework file objects for I/O requests, and if you know that some of the WDM I/O request packets (IRPs) that your driver receives do not include WDM file objects, the driver can set the WdfFileObjectCanBeOptional bit flag.

If your driver sets the WdfFileObjectWdfCanUseFsContext, WdfFileObjectWdfCanUseFsContext2, or WdfFileObjectWdfCannotUseFsContexts value and does not set the WdfFileObjectCanBeOptional bit flag, the framework's verifier reports an error for the following cases when the driver calls the WdfRequestGetFileObject method:

  • An IRP does not include a WDM file object.
  • An IRP includes a WDM file object, but the file object is different from the one that the file creation IRP included.
If the WdfFileObjectCanBeOptional bit flag is set, the framework's verifier ignores such cases.

Requirements

Requirement Value
Minimum KMDF version 1.0
Minimum UMDF version 2.0
Header wdfdevice.h (include Wdf.h)

See also

FILE_OBJECT

WDF_FILEOBJECT_CONFIG