Linux framebuffer example

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <fcntl.h>#include <linux/fb.h>#include <sys/mman.h>struct fb_fix_screeninfo FixedInfo;struct fb_var_screeninfo OrigVarInfo;static int FrameBufferFD = -1;void *FrameBuffer = (void *) -1;void test(void) {    /* open the framebuffer device */    FrameBufferFD = open("/dev/fb0", O_RDWR);    if (FrameBufferFD < 0) {        fprintf(stderr, "Error opening /dev/fb0/n");        exit(1);    }    /* Get the fixed screen info */    if (ioctl(FrameBufferFD, FBIOGET_FSCREENINFO, &FixedInfo)) {        fprintf(stderr, "error: ioctl(FBIOGET_FSCREENINFO) failed/n");        exit(1);    }    /* get the variable screen info */    if (ioctl(FrameBufferFD, FBIOGET_VSCREENINFO, &OrigVarInfo)) {        fprintf(stderr, "error: ioctl(FBIOGET_VSCREENINFO) failed/n");        exit(1);    }    if (FixedInfo.visual != FB_VISUAL_TRUECOLOR && FixedInfo.visual != FB_VISUAL_DIRECTCOLOR) {        fprintf(stderr, "non-TRUE/DIRECT-COLOR visuals (0x%x) not supported by this demo./n", FixedInfo.visual);        exit(1);    }    /*     * fbdev says the frame buffer is at offset zero, and the mmio region     * is immediately after.     */    /* mmap the framebuffer into our address space */    FrameBuffer = (void *) mmap(0, /* start */        FixedInfo.smem_len, /* bytes */        PROT_READ | PROT_WRITE, /* prot */        MAP_SHARED, /* flags */        FrameBufferFD, /* fd */        0 /* offset */);    if (FrameBuffer == (void *) - 1) {        fprintf(stderr, "error: unable to mmap framebuffer/n");        exit(1);    }}void close(void) {    munmap(FrameBuffer, FixedInfo.smem_len);    close(FrameBufferFD);}int main() {    test();    fprintf(stderr, "openFBDEV finish/n");    memset(FrameBuffer, 128, FixedInfo.smem_len);    sleep(5);    close();    fprintf(stderr, "closeFBDEV finish/n");    return 0;}