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PAGP_COMMIT_VIRTUAL callback function (videoagp.h)

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The AgpCommitVirtual function maps reserved virtual memory to an associated range of AGP-decodable physical addresses.

Syntax

PAGP_COMMIT_VIRTUAL PagpCommitVirtual;

PVOID PagpCommitVirtual(
  [in] IN PVOID HwDeviceExtension,
  [in] IN PVOID VirtualReserveContext,
  [in] IN ULONG Pages,
  [in] IN ULONG Offset
)
{...}

Parameters

[in] HwDeviceExtension

Pointer to the device extension of the miniport driver'.

[in] VirtualReserveContext

Identifies a reserved virtual address range. The context handle was obtained from AgpReserveVirtual.

[in] Pages

Specifies the number of pages of virtual memory to map.

[in] Offset

Specifies the page offset at which to commit the pages. The offset is applied to the reserved virtual address range that is identified by VirtualReserveContext.

Return value

AgpCommitVirtual returns the virtual address for the base of the committed pages if the mapping succeeded; otherwise returns NULL.

Remarks

Before calling AgpCommitVirtual to commit a range of virtual pages, you must do the following:

  • Call AgpReservePhysical to reserve a range of physical addresses for the GPU to use.
  • Call AgpCommitPhysical to map a portion (or all) of the reserved physical addresses to locked pages in system memory.
  • Call AgpReserveVirtual to reserve a range of virtual addresses that is associated with the range of physical addresses reserved by AgpReservePhysical.
After these items are completed, you can call AgpCommitVirtual to map a portion of the reserved virtual pages to pages that have already been mapped and locked by AgpCommitPhysical. You must not attempt to map a page of virtual addresses if the corresponding page of physical addresses has not already been mapped.

Video miniport drivers that run on Microsoft Windows 2000 should always commit a virtual range whose size is a multiple of 64 kilobytes. If you call AgpCommitVirtual to commit a virtual range that is not a multiple of 64 kilobytes, it can return an invalid virtual address.

On Windows XP and later, AgpCommitVirtual automatically expands the committed range so that it is a multiple of 64 kilobytes.

When a miniport driver calls AgpCommitVirtual, a portion of the virtual address range identified by VirtualReserveContext is mapped to physical addresses. The mapped portion begins Offset pages into the virtual address range that is identified by VirtualReserveContext.

Requirements

Requirement Value
Minimum supported client Available in Windows 2000 and later versions of the Windows operating systems.
Target Platform Desktop
Header videoagp.h (include Video.h)
IRQL PASSIVE_LEVEL

See also

AgpFreeVirtual

AgpReservePhysical

AgpReserveVirtual