DXGKDDI_QUERY_DEVICE_DESCRIPTOR callback function (dispmprt.h)

Article
10/21/2021

The DxgkDdiQueryDeviceDescriptor function returns a descriptor for a child device of a display adapter or for an external device (typically a monitor) connected to a child device of a display adapter.

Syntax

DXGKDDI_QUERY_DEVICE_DESCRIPTOR DxgkddiQueryDeviceDescriptor;

NTSTATUS DxgkddiQueryDeviceDescriptor(
  [in]      IN_CONST_PVOID MiniportDeviceContext,
  [in]      IN_ULONG ChildUid,
  [in, out] INOUT_PDXGK_DEVICE_DESCRIPTOR DeviceDescriptor
)
{...}

Parameters

[in] MiniportDeviceContext

A handle to a context block associated with a display adapter. The display miniport driver's DxgkDdiAddDevice function previously provided this handle to the DirectX graphics kernel subsystem.

[in] ChildUid

An integer that uniquely identifies the child device. The display miniport driver's DxgkDdiQueryChildRelations function previously provided this identifier to the display port driver.

[in, out] DeviceDescriptor

A pointer to a DXGK_DEVICE_DESCRIPTOR structure. The caller initializes the DescriptorLength and DescriptorBuffer members. If the child device has a type of TypeVideoOutput, the caller also initializes the DescriptorOffset member. On return, the caller-allocated buffer pointed to by the DescriptorBuffer member receives the descriptor.

Return value

DxgkDdiQueryDeviceDescriptor returns one of the following values:

Return code	Description
STATUS_SUCCESS	The function successfully returned the device descriptor.
STATUS_GRAPHICS_CHILD_DESCRIPTOR_NOT_SUPPORTED	The (onboard) child device identified by ChildUid does not support a descriptor.
STATUS_MONITOR_NO_DESCRIPTOR	The child device identified by ChildUid is connected to a monitor that does not support an EDID descriptor.
STATUS_MONITOR_NO_MORE_DESCRIPTOR_DATA	The child device identified by ChildUid is connected to a monitor that does support an EDID descriptor, but the descriptor does not have the EDID extension block specified by the DescriptorOffset and DescriptorLengthmembers of DeviceDescriptor.

Remarks

DxgkDdiQueryDeviceDescriptor must never write more than the number of bytes specified by DeviceDescriptor->DescriptorLength.

If the child device identified by ChildUid has a type of TypeVideoOutput, DxgkDdiQueryDeviceDescriptor returns a portion of the Extended Display Identification Data (EDID) for the monitor connected to the output. DeviceDescriptor->DescriptorOffset specifies the byte-offset into the EDID of the start of the data to be returned.

If the child device identified by ChildUid is not a video output, DxgkDdiQueryDeviceDescriptor returns a generic device descriptor; that is, it fills in the members of a DXGK_GENERIC_DESCRIPTOR structure.

The DxgkDdiQueryDeviceDescriptor function can be called several times for one child device. For a child device that has a connected monitor, the display port driver calls DxgkDdiQueryDeviceDescriptor during initialization to obtain the first 128-byte block of a monitor's EDID. Later the monitor class function driver (Monitor.sys) calls DxgkDdiQueryDeviceDescriptor to obtain selected portions (including the first 128-byte block) of that same monitor's EDID.

DxgkDdiQueryDeviceDescriptor should be made pageable.

Requirements

Requirement	Value
Minimum supported client	Available in Windows Vista and later versions of the Windows operating systems.
Target Platform	Desktop
Header	dispmprt.h
IRQL	PASSIVE_LEVEL