VGA-Compatible Miniport’s HwVidFindAdapter

A VGA-compatible miniport’s HwVidFindAdapter function (or registry HwVid..Callback) must set up the following in the VIDEO_PORT_CONFIG_INFO buffer:

• NumEmulatorAccessEntries, indicating the number of entries in the EmulatorAccessEntries array

• EmulatorAccessEntries, pointing to a static array containing the given number of EMULATOR_ACCESS_ENTRY-type elements, each describing a range of I/O ports hooked from the V86 emulator and, by default, forwarded to an SvgaHwIoPortXxx

  Each entry includes a starting I/O address, a range length, the size of access to be trapped (UCHAR, USHORT, or ULONG), whether the miniport supports input or output of string data through the I/O port(s), and the miniport-supplied SvgaHwIoPortXxx that actually validates and, possibly, transfers the data. Each SvgaHwIoPortXxx function handles read (IN or REP INSB/INSW/INSD) and/or write (OUT or REP OUTSB/OUTSW/OUTSD) transfers of UCHAR-, USHORT-, or ULONG-sized data.

• EmulatorAccessEntriesContext, a pointer to storage, such as an area in the miniport’s device extension, in which the miniport’s SvgaHwIoPortXxx can batch a sequence of application-issued instructions that require validation

• VdmPhysicalVideoMemoryAddress and VdmPhysicalVideoMemoryLength, describing a range of video memory that must be mapped into the VDM address space to support BIOS INT10 calls from full-screen MS-DOS applications

  The miniport driver can call the VideoPortInt10 function when such an application changes the video mode to one that the miniport driver’s adapter can support.

• HardwareStateSize, describing the minimum number of bytes required to store the hardware state for the adapter in response to an IOCTL_VIDEO_SAVE_HARDWARE_STATE request

  When the user switches a full-screen MS-DOS application to run in a window, the miniport driver must save the adapter state before the display driver regains control of the video adapter. Note that a VGA-compatible miniport driver also must support the reciprocal IOCTL_VIDEO_RESTORE_HARDWARE_STATE request because the user might switch the windowed application back to full-screen mode.

A VGA-compatible miniport’s emulator access entries specify subsets of its access ranges array for the adapter. The emulator access entries can be and usually are all I/O ports in the mapped access ranges array set up by its HwVidFindAdapter function. The access ranges it passes in calls to VideoPortSetTrappedEmulatorPorts, defining the current IOPM and determining the I/O ports that are directly accessible by a full-screen MS-DOS application, specify subsets of the miniport’s emulator access entries.