why i cant access all the pixels at vesa modes?
mov ax, 0x4F02; // vesa video mode
mov bx, 0x0101; // mode 640x480 256 colors
int 0x10; // video interupter
im drawing direct in screen with(in protected mode):
mov edi, 0x0A0000
add edi, 80000
mov al,0x0F ; the color of the pixel
mov [edi], al
in real mode:
mov ax, 0xA000; video adress
mov es, ax; segment address to es
mov di, 1200; pixel adress x + ( y * width )
mov al, 0x25; pixel colour
mov [es:di], al;
in the 13h mode i can draw at all the screen, but in the vesa i can draw only before +/- line(y) 100
this code configure the VBE mode, and draw a pixel at screen( you can draw at all screen with LFB ):
vbe_info:
.signature db "VBE2"; // must be "VESA" to indicate valid VBE support
.version resw 1; // VBE version; high byte is major version, low byte is minor version
.oem resd 1; // segment:offset pointer to OEM
.capabilities resd 1; // bitfield that describes card capabilities
.video_modes resd 1; // segment:offset pointer to list of supported video modes
.video_memory resw 1; // amount of video memory in 64KB blocks
.software_rev resw 1; // software revision
.vendor resd 1; // segment:offset to card vendor string
.product_name resd 1; // segment:offset to card model name
.product_rev resd 1; // segment:offset pointer to product revision
.reserved resb 222; // reserved for future expansion
.oem_data resb 256; // OEM BIOSes store their strings in this area
mode_info:
.attributes resw 1; // deprecated, only bit 7 should be of interest to you, and it indicates the mode supports a linear frame buffer.
.window_a resb 1; // deprecated
.window_b resb 1; // deprecated
.granularity resw 1; // deprecated; used while calculating bank numbers
.window_size resw 1;
.segment_a resw 1;
.segment_b resw 1;
.win_func_ptr resd 1; // deprecated; used to switch banks from protected mode without returning to real mode
.pitch resw 1; // number of bytes per horizontal line
.width resw 1; // width in pixels
.height resw 1; // height in pixels
.w_char resb 1; // unused...
.y_char resb 1; // ...
.planes resb 1;
.bpp resb 1; // bits per pixel in this mode
.banks resb 1; // deprecated; total number of banks in this mode
.memory_model resb 1;
.bank_size resb 1; // deprecated; size of a bank, almost always 64 KB but may be 16 KB...
.image_pages resb 1;
.reserved0 resb 1;
.red_mask resb 1;
.red_position resb 1;
.green_mask resb 1;
.green_position resb 1;
.blue_mask resb 1;
.blue_position resb 1;
.reserved_mask resb 1;
.reserved_position resb 1;
.direct_color_attributes resb 1;
.framebuffer resd 1; // physical address of the linear frame buffer; write here to draw to the screen
.off_screen_mem_off resd 1;
.off_screen_mem_size resw 1; // size of memory in the framebuffer but not being displayed on the screen
.reserved1 resb 206;
enable_vesa:
vbe_get_info:
mov ah, 4Fh; Super VGA support
mov al, 00h; Return Super VGA information
mov di, vbe_info; Pointer to buffer
int 0x10;
cmp ax, 0x4F ; BIOS doesn't support VBE?
jne error
get_mode_info:
mov ax, 4F01h; Return mode information
mov cx, 0x101;[vbe_info.video_modes]; first mode
mov di, mode_info; Pointer to buffer
int 0x10;
cmp ax, 0x4F ; BIOS doesn't support VBE?
jne error
set_mode:
mov ah, 0
mov ax, 0x4F02
mov ebx, [vbe_info.video_modes]; estore de modes pointer at ebx to can access as a adress
mov bx, [ebx+8]; 8/2 = 4th mode in the mode array!!!!!!!
int 0x10
draw:
;Assume first window is valid
mov ax, WORD [es:mode_info + 08h]
mov es, ax
;Example of how to change the window
mov ax, 4f05h
xor bx, bx
mov dx, 5 ;This is granularity units
int 10h
;fist atempt
mov edi, [mode_info.framebuffer]; framebuffer
add edi, 180050; pixel_offset = y * pitch + ( x * ( bpp/8 )) + framebuffer;
mov al,0x0F; the color of the pixel
mov [edi], al
mov si, msg;
call print
jmp $
msg db "finish", 0