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代码： 全选

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

    /* Open the file for reading and writing */
    fbfd = open("/dev/fb0", O_RDWR);
    if (fbfd < 0) {
        printf("Error: cannot open framebuffer device.\n");
        return -1;
    }
    printf("The framebuffer device was opened successfully.\n");

    /* Get fixed screen information */
    if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
        printf("Error reading fixed information.\n");
        return -1;
    }

    /* Get variable screen information */
    if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
        printf("Error reading variable information.\n");
        return -1;
    }

    /* Figure out the size of the screen in bytes */
    screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;

    /* Map the device to memory */
    fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED,
                                 fbfd, 0);

    if ((int)fbp == -1) {
        printf("Error: failed to map framebuffer device to memory.\n");
        return -1;
    }
    printf("The framebuffer device was mapped to memory successfully.\n");

    x = 100; y = 100; /* Where we are going to put the pixel */

    /* Figure out where in memory to put the pixel */
    location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) +
                    (y+vinfo.yoffset) * finfo.line_length;

    /* set RGBA value to the value */
    *(fbp + location) = 0; /* Some blue */
    *(fbp + location + 1) = 0; /* A little green */
    *(fbp + location + 2) = 255; /* A lot of red */
    *(fbp + location + 3) = 0; /* No transparency */

    munmap(fbp, screensize);
    close(fbfd);

    return 0;

}