DXGK_CONTEXTINFO structure (d3dkmddi.h)
The DXGK_CONTEXTINFO structure describes a device context.
Syntax
typedef struct _DXGK_CONTEXTINFO {
UINT DmaBufferSize;
UINT DmaBufferSegmentSet;
UINT DmaBufferPrivateDataSize;
UINT AllocationListSize;
UINT PatchLocationListSize;
UINT Reserved;
DXGK_CONTEXTINFO_CAPS Caps;
ULONG PagingCompanionNodeId;
} DXGK_CONTEXTINFO;
Members
DmaBufferSize
The size, in bytes, of the buffer of hardware commands that is sent through direct memory access (DMA) to the graphics processing unit (GPU).
The DMA buffer can grow and shrink after the context is created; however, the DMA buffer can never shrink smaller than the starting size that DmaBufferSize specifies.
DmaBufferSegmentSet
The identifiers of the segments where the DMA buffer should be made accessible to the GPU.
DmaBufferPrivateDataSize
The size, in bytes, of the driver-resident private data structure that is associated with each DMA buffer. Memory for this private data structure is allocated from nonpaged pool. If the driver specifies zero in DmaBufferPrivateDataSize, no memory is allocated for the private data structure.
The private data structure that is associated with a DMA buffer is initialized to zero when the DMA buffer is created. During the lifetime of the DMA buffer, the video memory manager never accesses the private data structure that is associated with the DMA buffer.
AllocationListSize
The starting number of elements in an array of allocations (that is, an array of DXGK_ALLOCATIONLIST structures). This number is the starting number of allocations that the driver requests to be in the pAllocationList members of the DXGKARG_PRESENT and DXGKARG_RENDER structures in calls to the driver's DxgkDdiPresent and DxgkDdiRender functions, respectively.
The allocation list can grow and shrink after the context is created; however, the allocation list can never shrink smaller than the starting size that AllocationListSize specifies.
PatchLocationListSize
The starting number of elements in an array of patch locations (that is, an array of D3DDDI_PATCHLOCATIONLIST structures) for the device in user mode and kernel mode. This number is the starting number of patch locations that the driver requests to be in the pPatchLocationListIn members of the DXGKARG_RENDER structures in calls to its DxgkDdiRender function.
The patch-location list can grow and shrink after the context is created; however, the patch-location list can never shrink smaller than the starting size that PatchLocationListSize specifies.
Reserved
This member is reserved and should be set to zero.
This member is available beginning with Windows 7.
Caps
Describes optional features supported by the context.
Supported starting with Windows 10.
PagingCompanionNodeId
Specifies the zero-based engine identifier of the engine to use for this context paging companion.
Supported starting with Windows 10.
Remarks
A display miniport driver specifies values for the DmaBufferSize and AllocationListSize members to guarantee that:
- The Microsoft DirectX graphics subsystem can use only one direct memory access (DMA) buffer to display (by using the display miniport driver's DxgkDdiPresent function) at least one RECT structure for all scenarios.
- The sizes of DMA and allocation-list buffers are large enough to hold at least one command that cannot be split across multiple buffers.
- The sizes of DMA and allocation-list buffers are large enough to avoid setup and DMA overhead.
If the driver sets DmaBufferSegmentSet to 0, the video memory manager allocates contiguous paged-locked memory, which is mapped write-combined memory, for the DMA buffers. Therefore, the GPU must access DMA buffers by using PCI cycles on computers where AGP transfers that occur outside the AGP aperture are not permitted.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows Vista |
| Header | d3dkmddi.h (include D3dkmddi.h) |