ID Number: Q74516
3.00 3.10
WINDOWS
Summary:
Note: This article assumes familiarity with the Interrupt 2FH Call-Out
Interface defined by the Microsoft Windows enhanced mode. For
information on the Interrupt 2FH interface, refer to Appendix C of the
"Microsoft Windows Device Driver Kit: Device Driver Adaptation Guide"
for Windows 3.1 and Appendix D of the "Microsoft Windows Device
Development Kit Virtual Device Adaptation Guide" for Windows 3.0.
A terminate-and-stay-resident program (TSRs) that loads a virtual
device (VxD) when Windows enhanced mode starts must specify the fully-
qualified filename to the virtual device file. This may not be
convenient for end users because the virtual device file must be
placed at a fixed place on the disk.
It is better to combine the TSR and the VxD together when the VxD is
built because the TSR can obtain the fully-qualified filename from
MS-DOS and provide the name to Windows at startup. The final product
is one EXE file that holds both the TSR and the VxD. The TSR is the
stub program with the VxD appended as an extended part of the EXE
file. This article describes the steps necessary to perform this
binding.
Please note, the binding method does not work if the TSR is in binary
(COM) format rather than EXE format. The TSR filename extension (EXE
or COM) is irrelevant. Therefore, while the TSR must be built in EXE
format, the filename may have either the EXE or the COM extension, as
desired.
The technique described here is used by the "Loadhi" program that
deals with EMM drivers. However, that program is too involved to be
used as an example here to demonstrate the binding process.
More Information:
The following three steps must be performed to bind the TSR and VxD:
1. In the TSR, fill the SIS_Virt_Dev_File_Ptr field of the
Win386_Startup_Info_Struc data structure with a pointer to a string
containing the fully-qualified filename of the load file. Obtain
this fully-qualified filename from the location starting at three
bytes beyond the end of the environment block. A code segment
resembling the following could be used:
mov ah, 62h
int 21h ; bx -> psp
mov es, bx
mov bx, 2ch ; offset of environment block pointer
mov es, es:[bx]
xor di, di ; es:di -> environment block
mov cx, -1
xor al, al ; search for null's
cld
env_search_loop:
repne scasb ; get past one null and stop
cmp byte ptr es:[di], 0 ; Q: end of env block?
jnz env_search_loop ; N: continue
add di, 3 ; Y: skip the last null &
; the word before
; the name.
lea si, InfoData ; a Win386_Startup_Info_Struc
mov word ptr [si].SIS_Virt_Dev_File_Ptr, di
mov word ptr [si][2].SIS_Virt_Dev_File_Ptr, es
More information about PSP and the environment block is available
in Ray Duncan's book "Advanced MS-DOS Programming" (Microsoft
Press).
2. In the module definition (DEF) file for the virtual device, specify
the filename for the TSR file in the STUB statement, as follows:
STUB <TSR file name>
For example, if the TSR is named TSRPRG.EXE, use the following
line:
STUB TSRPRG.EXE
3. In the MAKE file for the virtual device, build virtual device file
with an EXE extension instead of a 386 extension. For example:
link386 $(OBJS), VTSRPRGD.EXE $(LINKOPTIONS),,,VTSRPRGD.DEF
addhdr VTSRPRGD.EXE
Additional reference words: 3.00 3.10 DDKVXD