#include <unistd.h>

#include <stdio.h>

#include <fcntl.h>

#include <linux/fb.h>

#include <sys/mman.h>

int main () {

 int fp=0;

 struct fb_var_screeninfo vinfo;

 struct fb_fix_screeninfo finfo;

 long screensize=0;

 char *fbp = 0;

 int x = 0, y = 0;

 long location = 0;

 fp = open ("/dev/fb0",O_RDWR);

 if (fp < 0){

  printf("Error : Can not open framebuffer device/n");

  exit(1);

 }

 if (ioctl(fp,FBIOGET_FSCREENINFO,&finfo)){

  printf("Error reading fixed information/n");

  exit(2);

 }

 

 if (ioctl(fp,FBIOGET_VSCREENINFO,&vinfo)){

  printf("Error reading variable information/n");

  exit(3);

 }

  screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;

 /*这就是把fp所指的文件中从开始到screensize大小的内容给映射出来，得到一个指向这块空间的指针*/

 fbp =(char *) mmap (0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fp,0);

   if ((int) fbp == -1)

     {

        printf ("Error: failed to map framebuffer device to memory./n");

        exit (4);

     }

/*这是你想画的点的位置坐标,(0，0)点在屏幕左上角*/

  x = 0;

  y = 0;

  location = x * (vinfo.bits_per_pixel / 8) + y  *  finfo.line_length;

  *(fbp + location) = value;  /*直接填充赋值来显示*/

 

  munmap (fbp, screensize); /*解除映射*/

  close (fp);    /*关闭文件*/

  return 0;

}