Video Output Overlay Interface

#include <linux/fb.h>

struct v4l2_framebuffer fbuf;
unsigned int i;
int fb_fd;

if (-1 == ioctl(fd, VIDIOC_G_FBUF, &fbuf)) {
perror("VIDIOC_G_FBUF");
exit(EXIT_FAILURE);
}

for (i = 0; i < 30; i++) {
char dev_name[16];
struct fb_fix_screeninfo si;

snprintf(dev_name, sizeof(dev_name), "/dev/fb%u", i);

fb_fd = open(dev_name, O_RDWR);
if (-1 == fb_fd) {
switch (errno) {
case ENOENT: /* no such file */
case ENXIO:  /* no driver */
continue;

default:
perror("open");
exit(EXIT_FAILURE);
}
}

if (0 == ioctl(fb_fd, FBIOGET_FSCREENINFO, &si)) {
if (si.smem_start == (unsigned long)fbuf.base)
break;
} else {
/* Apparently not a framebuffer device. */
}

close(fb_fd);
fb_fd = -1;
}

/* fb_fd is the file descriptor of the framebuffer device
for the video output overlay, or -1 if no device was found. */