OSDEV:我如何使用vesa模式？

Question

嗨，我试图在我的操作系统中使用vesa模式，我正在使用本教程：以保护方式绘制

我有分辨率切换，但我不知道如何画一个像素。

这是我的代码：

kernel.asm

bits    32
section .text
align 4

dd 0x1BADB002
dd 0x04
dd -(0x1BADB002 + 0x04)

dd 0 ; skip some flags
dd 0
dd 0
dd 0
dd 0

dd 0 ; sets it to graphical mode
dd 800 ; sets the width
dd 600 ; sets the height
dd 32 ; sets the bits per pixel

push ebx
global start
extern kmain
start:
    cli
    call kmain
    hlt

kernel.c

#include "include/types.h"
kmain(){

}

先谢谢你

Answer 1

首先，您是否使用grub和多重引导来加载内核？如果是这样的话，那么VESA信息(以及视频内存地址(也称为线性帧缓冲区地址)将被复制到您可以在"kernel.c“文件中访问的多引导头结构中。帧缓冲区地址存储在索引22处的结构中。如果您想要对multiboot及其结构的完整规范，您可以在这里查看它们：https://www.gnu.org/software/grub/manual/multiboot/multiboot.html

否则，您可以在"kernel.c“文件中这样做：

void kmain(unsigned int* MultiBootHeaderStruct)
{
    //color code macros:
    #define red   0xFF0000
    #define green 0x00FF00
    #define blue  0x0000FF

    /*store the framebuffer address inside a new pointer
      the framebuffer is located at MultiBootHeaderStruct[22]*/
    unsigned int* framebuffer = (unsigned int*)MultiBootHeaderStruct[22];

    /*now to place a pixel at a specific screen position(screen index starts at 
      the top left of the screen which is at index 0), write a color value
      to the framebuffer pointer with a specified index*/
    
    //Sample Code:
    framebuffer[0] = red; //writes a red pixel(0xFF0000) at screen index 0
    framebuffer[1] = green; //writes a green pixel(0x00FF00) at screen index 1
    framebuffer[2] = blue; //writes a blue pixel(0x0000FF) at screen index 2
    /*this code should plot 3 pixels at the very top left of the screen
      one red, one green and one blue. If you want a specific color you can
      use the link I will provide at the bottom.*/

    
    //Sample code to fil the entire screen blue:
    int totalPixels = 480000; //800x600 = 480000 pixels total
    
    //loop through each pixel and write a blue color value to it
    for (int i = 0; i < totalPixels; i++)
    {
        framebuffer[i] = blue; //0x0000FF is the blue color value
    }
}

一个有用的颜色代码生成器：https://html-color-codes.info/注释。不要使用放置在生成颜色前面的"#“哈希标签，只使用它之后的值，并将代码中的颜色值放在"0x”之后，这意味着# of 0000应该放在您的代码中，为: 0xFF0000。

希望这能帮上忙。我也和VESA做过斗争，我想帮助那些也在挣扎的人。如果你想直接联系我寻求帮助，你可以增加我的不和，我可以尽力帮助我。我的用户名和标签是: Yeon#7984