DPMI question

["Rajiv Agrawal" <rajiva@hotmail.com>]

Hi John,

I saw your post on the DPMI sometime ago. I thought you may be able
to answer one of my questions. I have a 486 mother board, with Award
modular bios in there. I have PC-DOS running on it, and then it had
windows 95 installed. Now when I am doing a DOS only program, I use
the following code (from DPMI spec 0.9) after the next para:

The problems I see is that the values returned by AX flags is not zero
which means DPMI may not be supported. I am little confused as to why?
Did Windows95 did anything to DOS?  Also, do you see any problems with
the code. I will really appreciate your time.

Thanks a lot.

Rajiv
---------------------------listing-----------------------------

 

            Example Code

                 ;
                 ; Get the entry point address and save it
                 ;
                         mov     ax, 1687h
                         int     2Fh
                         test    ax, ax
                         jnz     Cant_Enter_PMode
                         mov     [PMode_Entry_Seg], es
                         mov     [PMode_Entry_Off], di

                 ;
                 ; Allocate memory for use by DOS extender if necessary
                 ; NOTE:  This code assumes that the program has already
                 ;        shrunk its memory block so that the DOS
                 ;        memory allocation call will work
                 ;
                         test    si, si
                         jz      Enter_PMode_Now
                         mov     bx, si
                         mov     ah, 48h
                         int     21h
                         jc      Cant_Enter_PMode
                         mov     es, ax 

                 ; Enter protected mode as a 16-bit program
                 ;
                 Enter_PMode_Now:
                         xor     ax, ax
                         call    DWORD PTR [PMode_Entry_Off]
                         jc      Cant_Enter_PMode
 
                 ;
 
**** I want to access PCI device in memory mapped mode
*********************My added code to above example code***********
****DWORD dwPhysical is physical address of the PCI device (from BAR)
****DWORD dwLength is length of the memory map

           push    di
           push    si
           mov     bx, WORD PTR [dwPhysical+2] ; Load arguments.
           mov     cx, WORD PTR [dwPhysical]
           mov     si, WORD PTR [dwLength+2]
           mov     di, WORD PTR [dwLength]
           mov     ax, 800h
           int     31h                         ; Issue DPMI call.
           jnc     short fine_return
           xor     bx, bx                      ; zero out return
           mov     cx, bx                      ; regs on error
   fine_return:
           mov     WORD PTR [dwLinear+2], bx   ; Return value.
           mov     WORD PTR [dwLinear], cx
           pop     si
           pop     di


---------------------------------------------------------
Get Your *Web-Based* Free Email at http://www.hotmail.com
---------------------------------------------------------4Œy