The DxgkDdiCreateAllocation function creates allocations of system or video memory.



NTSTATUS DxgkddiCreateallocation(



[in] A handle to a context block that is associated with a display adapter. The display miniport driver previously provided this handle to the Microsoft DirectX graphics kernel subsystem in the MiniportDeviceContext output parameter of the DxgkDdiAddDevice function.


[in/out] A pointer to a DXGKARG_CREATEALLOCATION structure that contains information for creating allocations.

Return Value

DxgkDdiCreateAllocation returns one of the following values:

Return code Description
DxgkDdiCreateAllocation successfully created the allocation.
Parameters that were passed to DxgkDdiCreateAllocation contained errors that prevented it from completing.
DxgkDdiCreateAllocation could not allocate memory that was required for it to complete.
The display miniport driver is not compatible with the user-mode display driver that initiated the call to DxgkDdiCreateAllocation.


After the user-mode display driver calls the pfnAllocateCb function, the DirectX graphics kernel subsystem calls the display miniport driver's DxgkDdiCreateAllocation function to create the allocations. The display miniport driver must interpret the private data (in the pPrivateDriverData member of the DXGK_ALLOCATIONINFO structure for each allocation) that is passed from the user-mode display driver and must determine the list of parameters that are required to create each allocation through the video memory manager. For more information about how the display miniport driver supplies these parameters to the video memory manager, see Specifying Segments When Creating Allocations.

The display miniport driver must return an allocation handle, which is typically a pointer to a private driver data structure that contains information about the allocation. The display miniport driver can call the DxgkCbGetHandleData function anytime to retrieve the private data for an allocation handle. Therefore, the display miniport driver is not required to maintain a private allocation handle table. In fact, we strongly discourage private handle tables because they could become stale or out of sync with the DirectX graphics kernel subsystem in display-mode-switch scenarios such as fast user switch, hot unplug, and so on.

The user-mode display driver assigns an allocation to either a resource or a device. To determine whether the allocation belongs to a resource, the display miniport driver can check whether the Resource bit-field flag is set in the Flags member of the DXGKARG_CREATEALLOCATION structure that the pCreateAllocation parameter of DxgkDdiCreateAllocation points to. If the allocation belongs to a resource, the display miniport driver can (but is not required to) return a resource handle, which is typically a pointer to a private driver data structure that describes the resource. If the DirectX graphics kernel subsystem calls DxgkDdiCreateAllocation to create an additional allocation for an existing resource, the hResource member of DXGKARG_CREATEALLOCATION contains the handle that was returned by the previous DxgkDdiCreateAllocation call for that resource. If necessary, the display miniport driver can change the resource handle during a call to DxgkDdiCreateAllocation.

If the user-mode display driver places a resource handle in a command buffer, the display miniport driver can retrieve the private data by calling DxgkCbGetHandleData. The display miniport driver can also enumerate all of the resource's child allocations by calling the DxgkCbEnumHandleChildren function.

Beginning with Windows 7, if a display miniport driver processes a call to the DxgkDdiCreateAllocation function to create allocations for GDI hardware acceleration, the driver should set the size of the allocation (including the pitch value for CPU visible allocations), pCreateAllocation->pAllocationInfo->Size.

The resources that are created in the DxgkDdiCreateAllocation call belong to the adapter and not to the device. The display miniport driver should not reference the device data anywhere within the private allocation and resource data structures. Because of surface sharing, a resource might be in use after the destruction of the device that the user-mode display driver created the resource from.

DxgkDdiCreateAllocation should be made pageable.

Allocating history buffers

Starting in Windows 8.1, when DxgkDdiCreateAllocation is called, the display miniport driver can set the DXGK_ALLOCATIONINFOFLAGS.HistoryBuffer member to indicate that the user-mode driver can manage the creation and destruction of history buffers.


Windows version Available in Windows Vista and later versions of the Windows operating systems.
Target Platform Desktop
Header d3dkmddi.h

See Also