Edit

Interrupts in Video Miniport Drivers

  • Article

A video miniport driver for an adapter that generates interrupts must implement a HwVidInterrupt routine. The miniport driver's DriverEntry routine should initialize the HwInterrupt member of the VIDEO_HW_INITIALIZATION_DATA structure to point to the interrupt handler.

The video port driver sets up an interrupt object for the video miniport driver if the adapter generates interrupts. Because the interrupt object is created and managed by the video port driver, a video miniport driver writer needs no further information about interrupt objects.

If the miniport driver's HwVidFindAdapter function finds that the video adapter does not actually generate interrupts or that it cannot determine a valid interrupt vector/level for the adapter, HwVidFindAdapter should set both InterruptLevel and InterruptVector in the VIDEO_PORT_CONFIG_INFO structure to zero.

When HwVidFindAdapter returns control, the video port driver checks the interrupt configuration members in VIDEO_PORT_CONFIG_INFO and, if both are zero, does not connect an interrupt for the miniport driver. Explicitly setting both interrupt configuration members to zero in HwVidFindAdapter disables the HwVidInterrupt entry point, if any, that was set up by the miniport driver's DriverEntry function.

Note that HwVidInterrupt can access the miniport driver's device extension since it is nonpaged. Depending on the design of the miniport driver, it might be impossible for other driver functions to share the device extension or a particular area of the device extension with HwVidInterrupt safely.

For example, suppose the miniport driver's HwVidStartIO function is accessing the device extension when the adapter interrupts, HwVidInterrupt is run on another processor, and HwVidInterrupt also accesses the device extension. If such a situation might occur, HwVidStartIO should call VideoPortSynchronizeExecution with a driver-supplied HwVidSynchronizeExecutionCallback function.

A video miniport driver should adhere to the following two rules:

  1. Whenever the miniport driver and hardware are in any state other than D0, the hardware never generates an interrupt.

  2. Because of Rule 1, a device driver ISR should never act on an interrupt if the power state is D3 (it should return FALSE).