PVIDEO_HW_START_IO callback function

Description

HwVidStartIO processes the specified VRP.

Parameters

HwDeviceExtension

Pointer to the miniport driver's per-adapter storage area. For more information, see Device Extensions.

RequestPacket

Pointer to a VIDEO_REQUEST_PACKET structure, which contains all the parameters originally passed to EngDeviceIoControl.

Return value

HwVidStartIO must return TRUE, indicating that it has completed the request.

Remarks

Every video miniport driver must have a HwVidStartIO function.

The video port driver calls HwVidStartIO in response to each GDI EngDeviceIoControl request, which originates in the corresponding display driver. When HwVidStartIO is called, the miniport driver owns the input video request packet until it completes the requested operation. HwVidStartIO must do the following:

1. Look at the IoControlCode member of the VRP to determine the operation being requested by the display driver.
2. Check that the VRP InputBufferLength and/or OutputBufferLength indicates a buffer that is large enough to satisfy the request. The miniport driver should return an error if either buffer is too small.
3. Satisfy the request.
4. Set the Status and Information members in the VRP and return TRUE.

The system video port driver serializes all requests. A miniport driver need not perform any serialization of its own unless it has a HwVidInterrupt function.

However, every miniport driver's HwVidStartIO function must complete each requested operation or set an appropriate error in the VRP's StatusBlock before it returns control.

HwVidStartIO should be made pageable.

See also

VIDEO_REQUEST_PACKET

Video Miniport Driver I/O Control Codes

VideoPortSynchronizeExecution