Note: This API calls are shared between DOS and Win16 personality.
DPMI is a shared interface for DOS applications to access Intel 80286+ CPUs services. DOS DMPI host provides core services for protected mode applications. Multitasking OS with DOS support also provides DMPI in most cases. Windows standard and extended mode kernel is a DPMI client app. Standard and extended mode kernel differs minimally and shares common codebase. Standard Windows kernel works under DOSX extender. DOSX is a specialized version of 16-bit DPMI Extender (but it is standard DPMI host). Standard mode is just DPMI client, exnhanced mode is DPMI client running under Virtual Machime Manager (really, multitasker which allow to run many DOS sessions). Both modes shares DPMI interface for kernel communication. The OS/2 virtual DOS Protected Mode Interface (VDPMI) device driver provides Version 0.9 DPMI support for virtual DOS machines. Win16 (up to Windows ME) provides Version 0.9 DPMI support. Windows in Standard Mode provides DPMI services only for Windows Applications, not DOS sessions.
DPMI host often merged with DPMI extender. Usually DPMI extender provide DPMI host standard services and DOS translation or True DPMI services.
Int 31H, AH=0CH, AL=00H
Version
1.0
Brief
Install Resident Service Provider Callback
Input
AX = 0C00H ES:(E)DI = selector:offset of 40-byte buffer with the following structure:
| Offset | Length | Contents |
|---|---|---|
| 00H | 8 | Descriptor for 16-bit data segment |
| 08H | 8 | Descriptor for 16-bit code segment |
| 10H | 2 | Offset of 16-bit callback procedure |
| 12H | 2 | Reserved |
| 14H | 8 | Descriptor for 32-bit data segment |
| 1CH | 8 | Descriptor for 32-bit code segment |
| 24H | 4 | Offset of 32-bit callback procedure |
Return
if function successful Carry flag = clear if function unsuccessful Carry flag = set AX = error code 8021H invalid value (access rights/type bytes invalid, or offset outside segment limits) 8025H invalid linear address (descriptor references a linear address range outside that allowed for DPMI clients) 8015H callback unavailable (host unable to allocate resources for resident handler initialization callback)
Notes
Protected mode resident service providers (protected mode TSRs) can provide services to 16-bit DPMI programs, 32-bit DPMI programs, or both. A resident service provider uses this function to request notification from the host whenever another DPMI program in the same virtual machine is loaded or terminated.
A DPMI client that uses this function declares its intent to provide resident protected mode services. The client must subsequently terminate and stay resident using Int 31H Function 0C01H. DPMI clients which intend to stay resident only to provide services to real mode programs should not use this function.The data structure provides room for a data descriptor, a code descriptor, and an offset for both 16-bit and 32-bit protected modes. The client can conveniently initialize the descriptor fields to valid values by fetching copies of its current code and data descriptors with Int 31H Function 000BH.
If only one mode is supported by the resident service provider, then the code descriptor for the unsupported mode should be initialized to zero.
This function is called on the locked protected mode stack.
For further details on programming of resident service providers, see that page.
See also
Note
Text based on http://www.delorie.com/djgpp/doc/dpmi/