PDRIVER_IO_PORT_ULONG callback function (video.h)
SvgaHwIoPortUlong traps an I/O port range to which a full-screen MS-DOS application in an x86-based machine is sending a sequence of ULONG-sized data.
Syntax
PDRIVER_IO_PORT_ULONG PdriverIoPortUlong;
VP_STATUS PdriverIoPortUlong(
ULONG_PTR Context,
ULONG Port,
UCHAR AccessMode,
PULONG Data
)
{...}
Parameters
Context
Specifies the miniport driver-determined context value that was set in the EmulatorAccessEntriesContext member of VIDEO_PORT_CONFIG_INFO.
Port
Specifies the mapped I/O port to be trapped.
AccessMode
Specifies the type of access allowed, which can be one or a combination (ORed) of the following values:
- EMULATOR_READ_ACCESS
- EMULATOR_WRITE_ACCESS
Data
Pointer to the ULONG data to be transferred.
Return value
SvgaHwIoPortUlong returns the final status of the operation.
Remarks
Only miniport drivers of VGA-compatible SVGA adapters have SvgaHwIoPortXxx functions. (See SVGA Functions.)
SvgaHwIoPortUlong intercepts any range access attempted by a full-screen MS-DOS application issuing either or both of the instructions OUT DX, EAX and IN EAX, DX.
If the miniport driver enables the Port range for direct access by calling VideoSetTrappedEmulatorPorts, its SvgaHwIoPortUlong function will not be called. Such an application then will have direct access to the I/O port range, unless the miniport driver disables the range with another call to VideoSetTrappedEmulatorPorts.
If one or more application-issued x86 IN or OUT instructions might affect the state of the VGA-compatible adapter sequencer register, miscellaneous output register, or any adapter-specific register and, thereby, cause the machine to hang, the miniport driver must not enable the port for direct access by calling VideoPortSetTrappedEmulatorPorts.
SvgaHwIoPortUlong must buffer subsequent instructions from the application and check that none can hang the machine. If the application issues any sequence of instructions that might hang the machine, SvgaHwIoPortUlong must discard the buffered instructions. Otherwise, it should output them, a ULONG at a time, to the specified, mapped I/O port.
SvgaHwIoPortUlong should be made pageable.
Requirements
| Requirement | Value |
|---|---|
| Target Platform | Desktop |
| Header | video.h (include Video.h) |