ata_id: skip ATA commands if we find an optical drive

Some drives are reported to erase CD-RW media with the ATA
commands we send.

Thanks to Christoph Stritt <phoenix@jobob.com> for his debugging.

Original bug is here:
  http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=556635

extras/ata_id/ata_id.c

@@ -38,6 +38,7 @@
 #include <linux/types.h>
 #include <linux/hdreg.h>
 #include <linux/fs.h>
+#include <linux/cdrom.h>
 #include <arpa/inet.h>
 
 #include "libudev.h"
@@ -210,6 +211,16 @@ static int disk_identify (struct udev *udev,
 		goto fail;
 	}
 
+	/*
+	 * do not confuse optical drive firmware with ATA commands
+	 * some drives are reported to blank CD-RWs
+	 */
+	if (ioctl(fd, CDROM_GET_CAPABILITY, NULL) >= 0) {
+		errno = EIO;
+		ret = -1;
+		goto fail;
+	}
+
 	/* So, it's a block device. Let's make sure the ioctls work */
 	if ((ret = ioctl(fd, BLKGETSIZE64, &size)) < 0)
 		goto fail;