vesa2.asm

linux下的任天堂模拟器代码。供大家参考。

    cmp bh,ah
    jb .scheck1b
    mov bh,ah
.scheck1b
    cmp bh,bl
    jb .scheck2b
    mov bh,bl
.scheck2b
    mov [fs:21h],bh

    mov al,16
    sub al,[fs:24h]
    mov ah,[fs:20h]
    sub ah,[fs:24h]
    mov bl,[fs:22h]
    sub bl,[fs:24h]
    mov bh,al
    cmp bh,ah
    jb .scheck1c
    mov bh,ah
.scheck1c
    cmp bh,bl
    jb .scheck2c
    mov bh,bl
.scheck2c
    mov [fs:23h],bh

    mov word[vesa2_clbit],0

    cmp byte[fs:20h],10
    jne .nottopbit
    mov word[vesa2_usbit],8000h
.nottopbit

    ; Process Red Stuff
    mov al,[fs:20h]         ; bit sizes = [fs:19h,21h,23h]
    mov cl,al
    mov bx,1
    shl bx,cl
    cmp byte[fs:19h],6
    jne .no6bit
    mov [vesa2_usbit],bx
    inc al
.no6bit
    or [vesa2_clbit],bx
    mov [vesa2_rpos],al
    dec al
    mov cl,al
    mov bx,001Fh
    cmp cl,0FFh
    je .shrr
    shl bx,cl
    jmp .shlr
.shrr
    shr bx,1
.shlr
    mov [vesa2_rfull],bx
    add al,5
    mov bx,1
    mov cl,al
    shl bx,cl
    mov [vesa2_rtrcl],bx
    xor bx,0FFFFh
    mov [vesa2_rtrcla],bx

;        mov ax,03h
;        int 10h
;        mov ax,[vesa2_rfull]
;        call printhex
;        jmp DosExit

    ; Process Green Stuff
    mov al,[fs:22h]
    mov cl,al
    mov bx,1
    shl bx,cl
    cmp byte[fs:21h],6
    jne .no6bitb
    mov [vesa2_usbit],bx
    inc al
.no6bitb
    or [vesa2_clbit],bx
    mov [vesa2_gpos],al
    dec al
    mov cl,al
    mov bx,001Fh
    cmp cl,0FFh
    je .shrg
    shl bx,cl
    jmp .shlg
.shrg
    shr bx,1
.shlg
    mov [vesa2_gfull],bx
    add al,5
    mov bx,1
    mov cl,al
    shl bx,cl
    mov [vesa2_gtrcl],bx
    xor bx,0FFFFh
    mov [vesa2_gtrcla],bx

    ; Process Blue Stuff
    mov al,[fs:24h]
    mov cl,al
    mov bx,1
    shl bx,cl
    cmp byte[fs:23h],6
    jne .no6bitc
    mov [vesa2_usbit],bx
    inc al
.no6bitc
    or [vesa2_clbit],bx
    mov [vesa2_bpos],al
    dec al
    mov cl,al
    mov bx,001Fh
    cmp cl,0FFh
    je .shrb
    shl bx,cl
    jmp .shlb
.shrb
    shr bx,1
.shlb
    mov [vesa2_bfull],bx
    add al,5
    mov bx,1
    mov cl,al
    shl bx,cl
    mov [vesa2_btrcl],bx
    xor bx,0FFFFh
    mov [vesa2_btrcla],bx

    xor word[vesa2_clbit],0FFFFh

    call genfulladdtab

    test word[fs:0h],10000000b  ; Check if linear available
    jnz .linearavailable
    mov edx,.nolframebuffer
    jmp VESA2EXITTODOS          ; None available

    ;---------------------------------------------;
     ; OK - now set the vesa 2 mode based on the ;
     ; information gleaned...                    ;
    ;---------------------------------------------;

    .linearavailable
    or word[vesamode],4000h  ; Convert mode to its LFB equivalent
    mov ebx,[fs:28h]         ; Read in physical base ptr

    mov cx,bx
    shr ebx,16
    mov si,[noblocks]
    xor edi,edi         ; Since noblocks = number of 64k blocks,
                        ; these lines leave si:di holding byte size
    mov eax,800h
    int 31h
    jnc .mappedphysicalarea
    mov edx,.unablemap
    jmp VESA2EXITTODOS  ; Failure!!!

.mappedphysicalarea
    shl ebx,16
    mov bx,cx
    mov [LFBpointer],ebx
    mov eax,ebx
    sub eax,[ZSNESBase]
    mov [VESAAddr],eax

    xor ecx,ecx
    xor edx,edx
    mov eax,4f02h
    movzx ebx,word[vesamode]
    int 10h             ; Set the vesa mode
    cmp ax,004fh
    jz .modesetok
    mov edx,.unableset
    jmp VESA2EXITTODOS  ; Failure!!!

.modesetok
;******************************* EXTRA BIT ****************************

;        cmp byte[.whichwin],1           ; Check if Write is at Window B
;        jne .nowinB
;
;        mov ax,4F05h
;        mov bx,1
;        mov dx,0
;        int 10h
;
;.nowinB

    ; Check logical scanline length
    mov eax,4f06h
    mov ebx,1
    int 10h
    cmp cx,[vesa2_x]
    je .correctwidth

    mov eax,4f06h           ; VBE Set/Get logical scan line length
    mov ebx,0               ; Set scan line length in pixels
    mov ecx, [vesa2_x]      ; Desired screen width
    int 10h
    cmp ax,04fh
    jz .correctwidth
    mov edx, .unablescan
    jmp VESA2EXITTODOS      ; Failure!!!

.correctwidth

;*************************** END OF EXTRA BIT *************************

    xor eax,eax
    mov ecx,1
    int 31h             ; Allocate a descriptor

    mov bx,ax           ; Move our selector into bx

    mov ecx,[LFBpointer]
    mov dx,cx
    shr ecx,16
    mov eax,7
    int 31h             ; Set our selector to LFB
    jnc .selectornowset
    mov edx,.unablelfb
    jmp VESA2EXITTODOS  ; Failure!!!

.selectornowset

    movzx ecx,word[noblocks]
    shl ecx,16          ; Multiply by 65536
    dec ecx             ; Necessary!!!
    mov dx,cx
    shr ecx,16          ; CX:DX size of screen
    mov eax,8
    int 31h             ; Set size of selector
    jnc .ok
    mov edx,.unablesets
    jmp VESA2EXITTODOS  ; Failure!!!

.ok
    lar ecx,ebx
    shr ecx,8
    and cl,60h
    or cl,93h
    and ch,0c0h         ; Keep granularity bit
    mov ax,9
    int 31h             ; Set selector access rights
    jnc .accessrightsset
    mov edx,.unablesetar
    jmp VESA2EXITTODOS

.accessrightsset
    mov [vesa2selec],bx

    cmp byte[vesa2red10],1
    je .red10
    mov eax,565
    jmp .red11
.red10
    mov eax,555
.red11
    push eax
    call Init_2xSaIMMX
    pop eax
    ret


SECTION .data
.nomemmessage db 'Unable to locate DOS memory.',0
.noint1message db 'Simulated real mode interrupt failed.',0
.novbemessage db 'VBE not detected!!',0
.novesamessage db 'VESA not detected!',0
.novesa2message db 'VESA 2.0 or greater required!',0
.oopsnoselector db 'Failed to allocate vesa display selector!',0
.outofmodelistspacemessage db 'Out of VESA2 mode list space!',0
.endoflist db 'This VESA2 mode does not work on your video card / driver.',0
.whichwin db 0
.modecheckfail db 'Real mode interrupt failure while checking vesa mode',0
.nolframebuffer db 'Linear Frame Buffer not Detected.',0
.unablemap db 'Unable to map physical area.',0
.unableset db 'Unable to initialize video mode.',0
.unablescan db 'Unable to set scan line length.',0
.unablelfb db 'Unable to set selector to LFB.',0
.unablesets db 'Unable to set size of selector.',0
.unablesetar db 'Unable to set selector access rights.',0

NEWSYM LFBpointer
    dd 0
NEWSYM noblocks
    dw 0
NEWSYM bytesperscanline
    dw 0
NEWSYM vesamode
    dw 0
;----------------------------------------------------------------------
;NEWSYM VESAmodelist
;   times 512 dw 0
;----------------------------------------------------------------------


SECTION .bss

NEWSYM VESAmodelist, times 512 resw 1
NEWSYM RMREGS
.edi  resd 1
.esi  resd 1
.ebp  resd 1
.esp  resd 1
.ebx  resd 1
.edx  resd 1
.ecx  resd 1
.eax  resd 1

.flags   resw 1
.es   resw 1
.ds   resw 1
.fs   resw 1
.gs   resw 1
.ip   resw 1
.cs   resw 1
.sp   resw 1
.ss   resw 1
.spare   times 20 resd 1
;----------------------------------------------------------------------