EMULATOR_ACCESS

EMULATOR_ACCESS_ENTRY

typedef struct _EMULATOR_ACCESS_ENTRY {

ULONG BasePort;

ULONG NumConsecutivePorts;

EMULATOR_PORT_ACCESS_TYPE AccessType;

UCHAR AccessMode;

UCHAR StringSupport;

PVOID Routine;

} EMULATOR_ACCESS_ENTRY, *PEMULATOR_ACCESS_ENTRY;

EMULATOR_ACCESS_ENTRY specifies an element in the EmulatorAccessEntries array set up in the VIDEO_PORT_CONFIG_INFO structure by drivers of VGA-compatible (SVGA) adapters on x86-based Windows NT® platforms.

Members

BasePort

Specifies the bus-relative physical address of the I/O port(s) to be hooked out by the V86 emulator. This value and the range of ports must fall within an access range of I/O ports already claimed in the registry by VideoPortGetAccessRanges or VideoPortVerifyAccessRanges.

NumConsecutivePorts

Specifies the number of consecutive ports to be hooked by the V86 emulator, starting at BasePort. This value is determined by how wide each hooked I/O port is considered to be. For example, if port addresses 0x3C0 and 0x3C1 are hooked as a single USHORT-addressable port, this value should be one.

AccessType

Specifies the size of the data transferred through the given I/O port as one of the following values:

Uchar
Ushort
Ulong

AccessMode

Specifies how the given I/O port can be accessed as one or a combination (ORed) of the following values:

EMULATOR_READ_ACCESS
EMULATOR_WRITE_ACCESS

The I/O port range must be accessible in at least one of the preceding modes.

StringSupport

Indicates whether the driver-supplied SvgaHwIoPortXxx function supports string accesses in cases for which many values of the given AccessType are “pumped” through an I/O port consecutively. If this member is set to TRUE, the Routine member must specify the entry point of a miniport-supplied SvgaHwIoPortXxxString function.

Routine

Points to the miniport’s SvgaHwIoPortXxx that handles accesses to the port(s) described in this structure.

Comments

VGA-compatible miniport drivers of SVGA video hardware in x86-based machines must define emulator access ranges, which a VGA-compatible miniport driver can set up with VideoPortSetTrappedEmulatorPorts to be accessed directly from full-screen MS-DOS™ applications for faster I/O. Such a driver must supply a set of SvgaHwIoPortXxx functions to validate any sequence of application-issued INs, INSB/INSW/INSDs, OUTs, and/or OUTSB/OUTSW/OUTSDs to each such I/O port range.

Data in each EMULATOR_ACCESS_ENTRY-type element is used to determine which I/O ports (memory locations at which adapter registers are accessible) in the miniport’s access ranges have been taken over (hooked out) by the V86 emulator on x86-based platforms. Values written to these locations by full-screen MS-DOS applications are trapped and forwarded to the miniport driver’s corresponding SvgaHwIoPortXxx function for validation before they are written to or read from the video adapter. However, the miniport can enable direct access by the application to particular I/O port ranges by calling VideoPortSetTrappedEmulatorPorts for performance reasons.