在ubuntu 12.04上测试framebuffer

在网上找了一段代码，测试framebuffer用，

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <fcntl.h>

#include <linux/fb.h>

#include <sys/mman.h>

#include <sys/ioctl.h>

int main()

{

int fbfd = 0;

struct fb_var_screeninfo vinfo;

struct fb_fix_screeninfo finfo;

long int screensize = 0;

char *fbp = 0;

int x = 0, y = 0;

long int location = 0;

int startx=0, starty=0;

int width, height;

// Open the file for reading and writing

fbfd = open("/dev/fb0", O_RDWR);

if (fbfd == -1) {

perror("Error: cannot open framebuffer device");

exit(1);

}

printf("The framebuffer device was opened successfully.\n");

// Get fixed screen information

if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo) == -1) {

perror("Error reading fixed information");

exit(2);

}

// Get variable screen information

if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo) == -1) {

perror("Error reading variable information");

exit(3);

}

printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);

// Figure out the size of the screen in bytes

screensize = vinfo.yres * finfo.line_length;

printf("screensize %ld\n", screensize);

// Map the device to memory

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");

exit(4);

}

printf("The framebuffer device was mapped to memory successfully.\n");

startx = 0; starty = 0; // Where we are going to put the pixel

width = 200;

height = 100;

// Figure out where in memory to put the pixel

for (y = starty; y < height + starty; y++)

for (x = startx; x < width + startx; x++) {

location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) +

(y+vinfo.yoffset) * finfo.line_length;

//printf("%ld \n", location);

if (vinfo.bits_per_pixel == 32) {

*(fbp + location) = 10; // Some blue

*(fbp + location + 1) = 15+(x-startx)/2; // A little green

*(fbp + location + 2) = 200-(y-starty)/5; // A lot of red

*(fbp + location + 3) = 0; // No transparency

} else { //assume 16bpp

int b = 10;

int g = (x-startx)/6; // A little green

int r = 31-(y-starty)/16; // A lot of red

unsigned short int t = r<<11 | g << 5 | b;

*((unsigned short int*)(fbp + location)) = t;

}

}

munmap(fbp, screensize);

close(fbfd);

getchar();

return 0;

}

编译之后运行不正常，我想是不是要到文本界面下去运行，因为图形界面下会对framebuffer干扰，

使用命令 sudo /etc/init.d/lightdm stop 关闭图形界面，在进入到文本界面时停在了 checking battery... 处就不动了，

搜索了一下，找到了解决方法，虽然此处hang住了，但仍可以按alt + F1 进入到登录界面，登录之后，运行上面的程序，显示一个色彩渐变的色块。