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|
vesa:
; print message
mov ebx, .msg
call print_str
; get vesa bios info
mov eax, dword[.vbe2]
mov dword[VESAINFO], eax ; move "VBE2" to start of vesainfo struct
mov ax, 0x4F00 ; get VESA BIOS information
mov di, VESAINFO ; struct buffer
int 0x10
cmp ax, 0x004F ; check ax for correct magic number
jne .fail_getinfo
mov eax, dword[.vesa]
cmp dword[VESAINFO], eax ; check if "VESA" is at start of stuct
jne .fail_getinfo
; print select message
mov ebx, .select_msg
call print_str
; get segment:offset pointer to video modes into gs:ebx
movzx ebx, word[VESAINFO+14]
mov ax, word[VESAINFO+16]
mov gs, ax
; convert modes to own structure
xor esi, esi ; number of avail modes
.mode_loop:
; get mode info
mov cx, [gs:ebx] ; video mode into cx
cmp cx, 0xFFFF ; 0xFFFF is terminator, no suitable mode has been found
je .mode_done
mov ax, 0x4F01 ; get VESA mode information
mov di, VESAMODE ; vesa mode info struct buffer
int 0x10
cmp ax, 0x004F ; check ax for correct magic number
jne .fail_modeinfo
mov al, byte[VESAMODE] ; get attributes
and al, 0b10000000 ; extract bit 7, indicates linear framebuffer support
jz .mode_next
mov al, byte[VESAMODE+25] ; get bpp (bits per pixel)
cmp al, 32
jne .mode_next
push ebx ; print_dec and print_str modify ebx
mov eax, esi
mov ebx, 12
mul ebx
mov edi, eax
add edi, OWNMODE
mov [edi+10], cx ; copy mode
; print selector
mov al, '['
call print_chr
mov eax, esi
add eax, 'a'
call print_chr
mov al, ']'
call print_chr
mov al, ' '
call print_chr
mov ax, [VESAMODE+16] ; copy pitch
mov [edi+0], ax
movzx eax, word[VESAMODE+18] ; copy width
mov [edi+2], ax
call print_dec
mov al, 'x'
call print_chr
movzx eax, word[VESAMODE+20] ; copy height
mov [edi+4], ax
call print_dec
call newline
mov eax, [VESAMODE+40] ; copy framebuffer
mov [edi+6], eax
pop ebx
inc esi
cmp esi, 'z'-'a' ; only print up to z
jg .mode_done
.mode_next:
add ebx, 2 ; increase mode pointer
jmp .mode_loop ; loop
.mode_done:
cmp esi, 0
je .fail_nomode
.input:
mov ebx, .select_prompt
call print_str
mov ah, 0x00 ; get keypress, blocking
int 0x16
call print_chr ; echo user input
movzx edi, al ; backup al
call newline
sub edi, 'a'
cmp edi, esi
jb .valid ; check validity
mov ebx, .invalid
call print_str
jmp .input
.valid:
; convert selected number to address
mov eax, edi
mov ebx, 12
mul ebx
add eax, OWNMODE
; copy to final gfx info location
mov ebx, [eax+0]
mov [GFXINFO+0], ebx
mov ebx, [eax+4]
mov [GFXINFO+4], ebx
mov bx, [eax+8]
mov [GFXINFO+8], bx
;mov edi, eax
;mov eax, [edi+6]
;call print_hex
;call newline
;mov eax, edi
;jmp $
;ret
; set mode
mov bx, [eax+10] ; video mode in bx (first 13 bits)
or bx, 1 << 14 ; set bit 14: enable linear frame buffer
and bx, 0b0111111111111111 ; clear deprecated bit 15
mov ax, 0x4F02 ; set VBE mode
int 0x10
ret
.msg: db "setting up vesa", 10, 13, 0
.vbe2: db "VBE2"
.vesa: db "VESA"
.select_msg: db "avaliable video modes:", 10, 13, 0
.select_prompt: db "select video mode: ", 0
.invalid: db "invalid input", 10, 13, 0
.fail_getinfo:
mov ebx, .fail_getinfo_msg
jmp .fail
.fail_modeinfo:
mov ebx, .fail_modeinfo_msg
jmp .fail
.fail_nomode:
mov ebx, .fail_nomode_msg
jmp .fail
.fail_getinfo_msg: db "failed getting vesa bios info", 10, 13, 0
.fail_modeinfo_msg: db "failed getting video mode info", 10, 13, 0
.fail_nomode_msg: db "no suitable video modes available", 10, 13, 0
.fail:
call print_str
jmp $
|
