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IoAllocateDriverObjectExtension function (wdm.h)

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The IoAllocateDriverObjectExtension routine allocates a per-driver context area, called a driver object extension, and assigns a unique identifier to it.

Syntax

NTSTATUS IoAllocateDriverObjectExtension(
  [in]  PDRIVER_OBJECT DriverObject,
  [in]  PVOID          ClientIdentificationAddress,
  [in]  ULONG          DriverObjectExtensionSize,
  [out] PVOID          *DriverObjectExtension
);

Parameters

[in] DriverObject

Pointer to a driver object to which the context area will be associated.

[in] ClientIdentificationAddress

Specifies a unique identifier for the context area to be allocated.

[in] DriverObjectExtensionSize

Specifies the length, in bytes, of the context area to be allocated.

[out] DriverObjectExtension

Pointer to, on completion, the allocated context area.

Return value

IoAllocateDriverObjectExtension returns one of the following NTSTATUS codes:

Return code Description
STATUS_SUCCESS
 Indicates that the routine allocated an extension of the requested size.
STATUS_INSUFFICIENT_RESOURCES
 Indicates that the memory could not be allocated for the driver object extension.
STATUS_OBJECT_NAME_COLLISION
 Indicates that a driver object extension with the given ClientIdentificationAddress already exists.

Remarks

Memory allocated by the system for the driver object extension is resident storage and is accessible from any IRQL. The allocated storage is automatically freed by the I/O manager when the driver object is deleted.

Callers of this routine must provide a unique identifier for ClientIdentificationAddress. To retrieve a pointer to the context area, a caller passes the ClientIdentificationAddress to IoGetDriverObjectExtension.

Requirements

Requirement Value
Minimum supported client Available starting with Windows 2000.
Target Platform Universal
Header wdm.h (include Wdm.h, Ntddk.h, Ntifs.h)
Library NtosKrnl.lib
DLL NtosKrnl.exe
IRQL <= DISPATCH_LEVEL

See also

IoGetDriverObjectExtension