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

int main(int argc, char **argv)
{
  int fbfd = 0;
  struct fb_var_screeninfo vinfo;
  struct fb_fix_screeninfo finfo;
  long int screensize = 0;
  unsigned char *fbp = 0;

  /* Open the file for reading and writing */
  fbfd = open("/dev/fb0", O_RDWR);
  if (!fbfd)
  {
    perror("open /dev/fb0");
    exit(1);
  }

  /* Get fixed screen information */
  if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo))
  {
    perror("finfo");
    exit(2);
  }
  printf("ID: %s, len: %d\n", finfo.id, finfo.smem_len);
  printf("Framebuffer type %d: ", finfo.type);
  switch (finfo.type)
  {
    case FB_TYPE_PACKED_PIXELS:
      printf("packed pixels\n");
      break;
    case FB_TYPE_PLANES:
      printf("non interleaved planes\n");
      break;
    case FB_TYPE_INTERLEAVED_PLANES:
      printf("interleaved planes\n");
      break;
    case FB_TYPE_TEXT:
      printf("text/attributes\n");
      break;
    case FB_TYPE_VGA_PLANES:
      printf("EGA/VGA planes\n");
      break;
    default:
      printf("unknown\n");
      break;
  }
  printf("Framebuffer visual %d: ", finfo.visual);
  switch (finfo.visual)
  {
    case FB_VISUAL_MONO01:
      printf("monochr 1=black 0=white\n");
      break;
    case FB_VISUAL_MONO10:
      printf("monochr 1=white 0=black\n");
      break;
    case FB_VISUAL_TRUECOLOR:
      printf("true colour\n");
      break;
    case FB_VISUAL_PSEUDOCOLOR:
      printf("pseudo colour\n");
      break;
    case FB_VISUAL_DIRECTCOLOR:
      printf("direct colour\n");
      break;
    case FB_VISUAL_STATIC_PSEUDOCOLOR:
      printf("fixed pseudo colour\n");
      break;
    default:
      printf("unknown\n");
      break;
  }
  printf("line len: %d, accel: %d\n", finfo.line_length, finfo.accel);

  /* Get variable screen information */
  if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo))
  {
    perror("vinfo");
    exit(3);
  }
  printf("xres: %d, yres: %d, ", vinfo.xres, vinfo.yres);
  printf("xoff: %d, yoff: %d\n", vinfo.xoffset, vinfo.yoffset);
  printf("bits per pixel: %d\n", vinfo.bits_per_pixel);
  printf("       Offset  Length  MSBR\n");
  printf("red    %7d %7d  %d\n", vinfo.red.offset,
	 vinfo.red.length, vinfo.red.msb_right);
  printf("green  %7d %7d  %d\n", vinfo.green.offset,
	 vinfo.green.length, vinfo.green.msb_right);
  printf("blue   %7d %7d  %d\n", vinfo.blue.offset,
	 vinfo.blue.length, vinfo.blue.msb_right);
  printf("transp %7d %7d  %d\n", vinfo.transp.offset,
	 vinfo.transp.length, vinfo.transp.msb_right);

  /* Figure out the size of the screen in bytes */
  screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
  printf("screen size: %d\n", screensize);

  /* Map the device to memory */
  fbp = (unsigned char *)mmap(0, screensize, PROT_READ | PROT_WRITE,
			      MAP_SHARED, fbfd, 0);       
  if ((int)fbp == -1)
  {
    perror("mmap");
    exit(4);
  }
  printf("screen mapped successfully\n");
  munmap(fbp, screensize);
  close(fbfd);
  return 0;
}