linux dev/fb

#include <stdio.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <unistd.h>

int main() {
    int fbfd = 0;
    struct fb_var_screeninfo vinfo;
    struct fb_fix_screeninfo finfo;
    long screensize = 0;
    char *fbp = 0;

    // 打开帧缓冲设备
    fbfd = open("/dev/fb0", O_RDWR);
    if (fbfd == -1) {
        perror("Error: cannot open framebuffer device");
        return 1;
    }

    // 获取固定屏幕信息
    if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
        perror("Error reading fixed information");
        close(fbfd);
        return 2;
    }

    // 获取可变屏幕信息
    if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
        perror("Error reading variable information");
        close(fbfd);
        return 3;
    }

    // 计算屏幕大小
    screensize = vinfo.yres * finfo.line_length;

    // 映射帧缓冲内存
    fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0);
    if ((int)fbp == -1) {
        perror("Error: failed to map framebuffer device to memory");
        close(fbfd);
        return 4;
    }

    // 设置像素（示例：将第一个像素设为红色）
    long location = 0;
    *(fbp + location) = 100;        // 蓝
    *(fbp + location + 1) = 150;    // 绿
    *(fbp + location + 2) = 200;    // 红
    *(fbp + location + 3) = 0;      // 透明度

    // 解除映射并关闭设备
    munmap(fbp, screensize);
    close(fbfd);
    return 0;
}