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Text File | 1996-12-16 | 15.4 KB | 488 lines

Small doc on using SVGA with DOS32. 1. Check if the videomode we want is supported on the computer. The problem here is that we need some low memory, where we can let the VBE put some info about the mode. This is solved, however, by using the 8k buffer that DOS32 uses for file I/O. (We'll make a near ptr to the videomemory when we're at function 0ee02h anyway.) --->8----- API.DOC ---------- GET DOS32 ADDRESS INFORMATION V3.01+ IN: AX = EE02h OUT: EBX = 32bit linear address of the program segment EDX = Total size in bytes of the programs .EXE file after linking. ESI = Offset address of PSP ( Program Segment Prefix ) EDI = Offset address of Program Environment ECX = Offset address of the programs .EXE file name and path (in ASCIZ format, i.e. terminates with a zero) AX = Real mode segment value of the 8Kb buffer that is used by the file read/write services. ---8<----- API.DOC ---------- The values we need here are AX and EBX, we need to make a near pointer out of that realmode segment value. lowmemptr dd ? lowmemseg dw ? linearadr dd ? videomem dd ? mov eax,0ee02h int 31h mov lowmemseg,ax mov linearadr,ebx push ax ;\ xor eax,eax ; > Clears the high bits of eax pop ax ;/ shl eax,4 ; Makes eax the absolute address of the RM segment sub eax,ebx ; Makes eax a near pointer to the RM segment mov lowmemptr,eax mov eax,0a0000h sub eax,ebx mov videomem,eax Now when we have our segment, and accompanying near pointer, we can make a real mode callback to the VBE. --->8----- API.DOC ---------- ...expects a pointer to a real mode call structure whish is used to passing all registers to and from the real mode switch. The format of the structure is defined as: Offset Register 00h EDI 04h ESI 08h EBP 0Ch Reserved by system 10h EBX 14h EDX 18h ECX 1Ch EAX 20h Flags 22h ES 24h DS 26h FS 28h GS 2Ah IP 2Ch CS 2Eh SP 30h SS Simulate a Real Mode interrupt V3.00+ IN: AX = 0300h BL = Interrupt number BH = Flags Bit 0 = 1 resets the interrupt controller and A20 line. Other flags reserved and must be 0 CX = Number of words to copy from protected mode to real mode stack ES:EDI = Selector:Offset of real mode call structure OUT: If function was successful: Carry flag is clear. ES:(E)DI = Selector:Offset of modified real mode call structure If function was not successful: Carry flag is set. ---8<----- API.DOC ---------- So, we need a structure defined as described in API.DOC: --->8----- GFX.ASM ---------- _ label _edi label dword _di label word _dih db ? _dil db ? _edih db ? _edil db ? _esi label dword _si label word _sih db ? _sil db ? _esih db ? _esil db ? _ebp label dword _bp label word _bph db ? _bpl db ? _ebph db ? _ebpl db ? _reserv dd ? _ebx label dword _bx label word _bh db ? _bl db ? _ebh db ? _ebl db ? _edx label dword _dx label word _dh db ? _dl db ? _edh db ? _edl db ? _ecx label dword _cx label word _ch db ? _cl db ? _ech db ? _ecl db ? _eax label dword _ax label word _ah db ? _al db ? _eah db ? _eal db ? _flags dw ? _es dw ? _ds dw ? _fs dw ? _gs dw ? _ip dw ? _cs dw ? _sp dw ? _ss dw 0 ---8<----- GFX.ASM ---------- --->8----- INTERRUP.LST ---------- --------V-104F00----------------------------- INT 10 - VESA SuperVGA BIOS (VBE) - GET SuperVGA INFORMATION AX = 4F00h ES:DI -> buffer for SuperVGA information (see #0063) Return: AL = 4Fh if function supported AH = status 00h successful ES:DI buffer filled 01h failed ---VBE v2.0--- 02h function not supported by current hardware configuration 03h function invalid in current video mode Desc: determine whether VESA BIOS extensions are present and the capabilities supported by the display adapter SeeAlso: AX=4E00h,AX=4F01h,AX=7F00h,AX=A00Ch Index: installation check;VESA SuperVGA Format of SuperVGA information: Offset Size Description (Table 0063) 00h 4 BYTEs (ret) signature ("VESA") (call) VESA 2.0 request signature ("VBE2"), required to receive version 2.0 info 04h WORD VESA version number (one-digit minor version) 06h DWORD pointer to OEM name "761295520" for ATI 0Ah DWORD capabilities flags (see #0064) 0Eh DWORD pointer to list of supported VESA and OEM video modes (list of words terminated with FFFFh) 12h WORD total amount of video memory in 64K blocks ---VBE v1.x --- 14h 236 BYTEs reserved ---VBE v2.0 --- 14h WORD OEM software version 16h DWORD pointer to vendor name 1Ah DWORD pointer to product name 1Eh DWORD pointer to product revision string 22h 222 BYTEs reserved 100h 256 BYTEs OEM scratchpad Notes: the list of supported video modes is stored in the reserved portion of the SuperVGA information record by some implementations, and it may thus be necessary to either copy the mode list or use a different buffer for all subsequent VESA calls the 1.1 VESA document specifies 242 reserved bytes at the end, so the buffer should be 262 bytes to ensure that it is not overrun; for v2.0, the buffer should be 512 bytes the S3 specific video modes will most likely follow the FFFFh terminator at the end of the standard modes. A search must then be made to find them, FFFFh will also terminate this second list Bitfields for VESA capabilities: Bit(s) Description (Table 0064) 0 DAC can be switched into 8-bit mode 1 non-VGA controller 2 programmed DAC with blank bit 3-31 reserved ---8<----- INTERRUP.LST ---------- Now, we need to set up the values to do the callback: mov ax,lowmemseg mov _es,ax mov _di,0 mov _ax,4f00h mov eax,300h mov ebx,10h xor ecx,ecx lea edi,_ ;our RM callback structure int 31h If all went well, (ah=00h, al=4fh), we should now have a realmode seg:ofs ptr to a word list of supported video modes. Make it a near ptr and scan it to see if what we want is available: cmp _ax,4fh jne vbe_error xor eax,eax xor ebx,ebx mov ax,word ptr lowmemptr[0eh] mov bx,word ptr lowmemptr[10h] shl ebx,4 add eax,ebx sub eax,linearadr mov esi,eax mov bx,101h ;desired video mode loop1: lodsw cmp ax,-1 je mode_not_supported cmp ax,bx jne loop1 We've got our video mode! :) 2. We need the window granularity of this mode to do proper bankswitching. This means interfacing the VBE, and using the RM buffer again. --->8----- INTERRUP.LST ---------- --------V-104F01----------------------------- INT 10 - VESA SuperVGA BIOS - GET SuperVGA MODE INFORMATION AX = 4F01h CX = SuperVGA video mode ES:DI -> 256-byte buffer for mode information (see #0065) Return: AL = 4Fh if function supported AH = status 00h successful ES:DI buffer filled 01h failed Desc: determine the attributes of the specified video mode SeeAlso: AX=4F00h,AX=4F02h Format of VESA SuperVGA mode information: Offset Size Description (Table 0065) 00h WORD mode attributes (see #0066) 02h BYTE window attributes, window A (see #0067) 03h BYTE window attributes, window B (see #0067) 04h WORD window granularity in KB 06h WORD window size in KB 08h WORD start segment of window A 0Ah WORD start segment of window B 0Ch DWORD -> FAR window positioning function (equivalent to AX=4F05h) 10h WORD bytes per scan line ---remainder is optional for VESA modes in v1.0/1.1, needed for OEM modes--- 12h WORD width in pixels (graphics) or characters (text) 14h WORD height in pixels (graphics) or characters (text) 16h BYTE width of character cell in pixels 17h BYTE height of character cell in pixels 18h BYTE number of memory planes 19h BYTE number of bits per pixel 1Ah BYTE number of banks 1Bh BYTE memory model type (see #0068) 1Ch BYTE size of bank in KB 1Dh BYTE number of image pages 1Eh BYTE reserved (0) ---VBE v1.2+--- 1Fh BYTE red mask size 20h BYTE red field position 21h BYTE green mask size 22h BYTE green field size 23h BYTE blue mask size 24h BYTE blue field size 25h BYTE reserved mask size 26h BYTE reserved mask position 27h BYTE direct color mode info bit 0: color ramp is programmable bit 1: bytes in reserved field may be used by application ---VBE v2.0 --- 28h DWORD physical address of linear video buffer 2Ch DWORD pointer to start of offscreen memory 30h WORD KB of offscreen memory 32h 206 BYTEs reserved (0) Bitfields for VESA SuperVGA mode attributes: Bit(s) Description (Table 0066) 0 mode supported 1 optional information available 2 BIOS output supported 3 set if color, clear if monochrome 4 set if graphics mode, clear if text mode ---VBE v2.0 --- 5 mode is not VGA-compatible 6 bank-switched mode not supported 7 linear framebuffer mode supported Bitfields for VESA SuperVGA window attributes: Bit(s) Description (Table 0067) 0 exists 1 readable 2 writable 3-7 reserved (Table 0068) Values for VESA SuperVGA memory model type: 00h text 01h CGA graphics 02h HGC graphics 03h 16-color (EGA) graphics 04h packed pixel graphics 05h "sequ 256" (non-chain 4) graphics 06h direct color (HiColor, 24-bit color) 07h YUV (luminance-chrominance, also called YIQ) 08h-0Fh reserved for VESA 10h-FFh OEM memory models ---8<----- INTERRUP.LST ---------- mov ax,lowmemseg mov _es,ax mov _di,0 mov _ax,4f01h mov _cx,101h ;video mode mov eax,300h mov ebx,10h xor ecx,ecx lea edi,_ ;our RM callback structure int 31h If all is OK, we will have the wgran parameter at offset 4 in the RM segment. However, it is specified in KB, so we need to shl with 10 to get byte size. wgran dd ? cmp _ax,4fh jne vbe_error xor ebx,ebx mov bx,word ptr lowmemptr[4] shl ebx,10 mov wgran,ebx We've got granularity. :) 3. Allocate memory for our virtual screen and switch to the SVGA mode. This is really simple to do. --->8----- API.DOC ---------- ALLOCATE A MEMORY BLOCK V3.00+ The entire application code,data and stack is initially contained in one large memory block. This service here is used for allocating extra memory blocks for the application. IN: AX = EE42h EDX = Size of the memory block requested to allocate in bytes. OUT: EAX = The actual allocated size of the memory block in bytes EDX = Near pointer to the base address of the block relative to the main program segment. If the returned size was less than the requested size then the Carry flag is set otherwise the carry flag is cleared. Notes: o The value expected in EDX will be rounded off to the next 4KB boundary. Example, allocating 51001h bytes will actually allocate 52000h bytes. o Never call this function in a interrupt handler or after using the terminated and stay resident function ( AX=EE30h ). o If EAX is returned with zero then no memory was allocated and contents of EDX are undefined. o The function will fail if the requested size is zero. o No more than 64 allocations can be made. If the application requires a faster more versatile memory management then please use Peter Anderson's memory sub-functions from PAL library. See example files on how to use. This function here is should used a minimum number of times. o When not running under a DPMI server ( i.e Raw,XMS or VCPI ) then extended memory is allocated before conventional memory is. For example, if there is no more extended memory free then conventional memory will be allocated. In either case DOS32 sets up the 386 page tables such that the allocated memory is addressed in a straight linear block when it may actually be physically scattered throughout RAM. ---8<----- API.DOC ---------- vscreen dd ? mov eax,0ee42h mov edx,640*480 int 31h jc not_enough_memory mov vscreen,edx mov eax,4f02h mov ebx,101h ;our video mode.. int 10h Done. :) 4. Put something on the virtual screen. 5. Flip the virtual screen out to video memory. This is not the best way to do it, but it's fairly simple to understand. flip proc push eax ebx ecx edx esi edi ebp xor dx,dx ;bank counter xor ebx,ebx ;used to clear the buffer mov ebp,640*480 ;bytes left to move-counter mov esi,vscreen mov edi,videomem outer_loop: call setbank cmp ebp,65536 jae mov64k mov ecx,ebp sub ebp,ecx ;update counter shr ecx,2 ;divide by 4 to get number of dwords to move jmp loop_start mov64k: sub ebp,65536 mov ecx,16384 loop_start: mov eax,[esi] ;read a dword from the buffer mov [edi],eax ;and write it to video mem mov [esi],ebx ;clear the dword in the buffer add esi,4 ;update pointers add edi,4 ;update pointers dec ecx jnz loop_start ;loop for 16384 times, this will move 65536 bytes.. inc edx ;increase bank counter sub edi,65536 cmp ebp,3 ;check if we have more than 3 bytes left, ja outer_loop ;if so then jump up or ebp,ebp ;are we completely done? jz flpbye ;yes, then quit.. mov ecx,ebp ;otherwise, move these bytes to video mem loop2_start: ;this loop is used to move the bytes left mov al,[esi] ;read one byte from buffer mov [edi],al ;and write to video mem mov [esi],bl ;clear buffer inc esi ;increase source pointer inc edi ;increase destination pointer dec ecx jnz loop2_start ;play it again, Sam! flpbye: pop ebp edi esi edx ecx ebx eax retn flip endp setbank proc push ax bx dx mov ax,4f05h xor bx,bx int 10h pop dx bx ax retn setbank endp OK! That's all folks. Check out DOS32VBE.ASM included in the package, I've put together the different sources listed in this document, and made a simple filling-routine. Enjoy, and feel free to send comments to stuge@kuai.se! :) -- Peter Stuge aka CareBear\ of ComeDY