The link worked for me, but the code base is small enough to post:

// gcc -o cdrom-test cdrom-test.c
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/cdrom.h>
int
main (int argc, char **argv)
{
char *program;
char *device;
int fd; /* file descriptor for CD-ROM device */
int status; /* return status for system calls */
int verbose = 0;
program = argv[0];
++argv;
--argc;
if (argc < 1 || argc > 2) {
fprintf (stderr, "usage: %s [-v] <device>\n",
program);
exit (1);
}

if (strcmp (argv[0], "-v") == 0) {
verbose = 1;
++argv;
--argc;
}

device = argv[0];

/* open device */
fd = open(device, O_RDONLY | O_NONBLOCK);
if (fd < 0) {
fprintf (stderr, "%s: open failed for `%s': %s\n",
program, device, strerror (errno));
exit (1);
}
/* Check CD player status */
printf ("Drive status: ");
status = ioctl (fd, CDROM_DRIVE_STATUS, CDSL_CURRENT);
if (status<0) {
perror(" CDROM_DRIVE_STATUS");
} else switch(status) {
case CDS_DISC_OK:
printf ("Ready.\n");
break;
case CDS_TRAY_OPEN:
printf ("Tray Open.\n");
break;
case CDS_DRIVE_NOT_READY:
printf ("Drive Not Ready.\n");
break;
default:
printf ("This Should not happen!\n");
break;
}
status = ioctl (fd, CDROM_DRIVE_STATUS, 0);
if (status<0) {
perror(" CDROM_DRIVE_STATUS");
} else switch(status) {
case CDS_DISC_OK:
printf ("Disc present.");
break;
case CDS_NO_DISC:
printf ("Empty slot.");
break;
case CDS_TRAY_OPEN:
printf ("CD-ROM tray open.\n");
break;
case CDS_DRIVE_NOT_READY:
printf ("CD-ROM drive not ready.\n");
break;
case CDS_NO_INFO:
printf ("No Information available.");
break;
default:
printf ("This Should not happen!\n");
break;
}
status = ioctl (fd, CDROM_DISC_STATUS);
if (status<0) {
perror(" CDROM_DISC_STATUS");
}
switch (status) {
case CDS_AUDIO:
printf ("\tAudio disc.\t");
break;
case CDS_DATA_1:
case CDS_DATA_2:
printf ("\tData disc type %d.\t", status-CDS_DATA_1+1);
break;
case CDS_XA_2_1:
case CDS_XA_2_2:
printf ("\tXA data disc type %d.\t", status-CDS_XA_2_1+1);
break;
default:
printf ("\tUnknown disc type 0x%x!\t", status);
break;
}
status = ioctl (fd, CDROM_MEDIA_CHANGED, 0);
if (status<0) {
perror(" CDROM_MEDIA_CHANGED");
}
switch (status) {
case 1:
printf ("Changed.\n");
break;
default:
printf ("\n");
break;
}
{
int foo;
dvd_struct dvd;
dvd.type = DVD_STRUCT_COPYRIGHT;
dvd.copyright.layer_num = 0;
status = ioctl( fd, DVD_READ_STRUCT, &dvd );
foo = dvd.copyright.cpst;
if (status < 0)
{
perror ("Not a DVD");
} else switch (foo) {
case 0:
printf ("DVD not encrypted\n");
break;
case 1:
printf ("DVD encrypted\n");
break;
default:
printf ("Shouldn't happen\n");
break;
}
printf ("RMI is: %#02x\n", dvd.copyright.rmi);
}
/* close device */
status = close (fd);
if (status != 0) {
fprintf (stderr, "%s: close failed for `%s': %s\n",
program, device, strerror (errno));
exit (1);
}

exit (0);
}