Install Resident Service Provider Callback
![[1.0]](../1.0.gif)
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.
Call With
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 |
Returns
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
- 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.