cdrom_id: Fix detection of reblanked DVD+RW and DVD-RAM

Once formatted, DVD+RW and DVD-RAM discs are always reported "complete" by the
drive. Check the if the Volume Descriptor or Volume Descriptor Anchor sectors
are empty, and if so, set the status to blank. If the disc is unformatted the
blank status is maintained and no reads are issued. If the disc is formatted and
read command fails, the status remains set to complete to avoid accidental
blanking.

Bug-Ubuntu: https://launchpad.net/bugs/581925

Signed-off-by: Martin Pitt <martin.pitt@ubuntu.com>

1 files changed, 105 insertions, 0 deletions

diff --git a/extras/cdrom_id/cdrom_id.c b/extras/cdrom_id/cdrom_id.c
index 2bea2e4b0c..9c4f6f31b4 100644
--- a/extras/cdrom_id/cdrom_id.c
+++ b/extras/cdrom_id/cdrom_id.c
@@ -532,6 +532,111 @@ static int cd_media_info(struct udev *udev, int fd)
 	if (!cd_media_cd_rom)
 		cd_media_state = media_status[header[2] & 3];
 
+	/* DVD+RW discs once formatted are always "complete", DVD-RAM are
+	 * "other" or "complete" if the disc is write protected; we need to
+	 * check the contents if it is blank */
+	if ((cd_media_dvd_plus_rw || cd_media_dvd_plus_rw_dl || cd_media_dvd_ram) && (header[2] & 3) > 1) {
+		unsigned char buffer[17 * 2048];
+		unsigned char result, len;
+		int block, offset;
+
+		if (cd_media_dvd_ram) {
+			/* a write protected dvd-ram may report "complete" status */
+
+			unsigned char dvdstruct[8];
+			unsigned char format[12];
+
+			scsi_cmd_init(udev, &sc, dvdstruct, sizeof(dvdstruct));
+			scsi_cmd_set(udev, &sc, 0, 0xAD);
+			scsi_cmd_set(udev, &sc, 7, 0xC0);
+			scsi_cmd_set(udev, &sc, 9, sizeof(dvdstruct));
+			scsi_cmd_set(udev, &sc, 11, 0);
+			err = scsi_cmd_run(udev, &sc, fd, dvdstruct, sizeof(dvdstruct));
+			if ((err != 0)) {
+				info_scsi_cmd_err(udev, "READ DVD STRUCTURE", err);
+				return -1;
+			}
+			if (dvdstruct[4] & 0x02) {
+				cd_media_state = media_status[2];
+				info(udev, "write-protected DVD-RAM media inserted\n");
+				goto determined;
+			}
+
+			/* let's make sure we don't try to read unformatted media */
+			scsi_cmd_init(udev, &sc, format, sizeof(format));
+			scsi_cmd_set(udev, &sc, 0, 0x23);
+			scsi_cmd_set(udev, &sc, 8, sizeof(format));
+			scsi_cmd_set(udev, &sc, 9, 0);
+			err = scsi_cmd_run(udev, &sc, fd, format, sizeof(format));
+			if ((err != 0)) {
+				info_scsi_cmd_err(udev, "READ DVD FORMAT CAPACITIES", err);
+				return -1;
+			}
+
+			len = format[3];
+			if (len & 7 || len < 16) {
+				info(udev, "invalid format capacities length\n");
+				return -1;
+			}
+
+			switch(format[8] & 3) {
+			    case 1:
+				info(udev, "unformatted DVD-RAM media inserted\n");
+				/* This means that last format was interrupted
+				 * or failed, blank dvd-ram discs are factory
+				 * formatted. Take no action here as it takes
+				 * quite a while to reformat a dvd-ram and it's
+				 * not automatically started */
+				goto determined;
+
+			    case 2:
+				info(udev, "formatted DVD-RAM media inserted\n");
+				break;
+
+			    case 3:
+				cd_media = 0; //return no media
+				info(udev, "format capacities returned no media\n");
+				return -1;
+			}
+		}
+
+		/* Take a closer look at formatted media (unformatted DVD+RW
+		 * has "blank" status", DVD-RAM was examined earlier) and check
+		 * for ISO and UDF PVDs or a fs superblock presence and do it
+		 * in one ioctl (we need just sectors 0 and 16) */
+		scsi_cmd_init(udev, &sc, buffer, sizeof(buffer));
+		scsi_cmd_set(udev, &sc, 0, 0x28);
+		scsi_cmd_set(udev, &sc, 5, 0);
+		scsi_cmd_set(udev, &sc, 8, 17);
+		scsi_cmd_set(udev, &sc, 9, 0);
+		err = scsi_cmd_run(udev, &sc, fd, buffer, sizeof(buffer));
+		if ((err != 0)) {
+			info_scsi_cmd_err(udev, "READ FIRST 32 BLOCKS", err);
+			return -1;
+		}
+
+		/* if any non-zero data is found in sector 16 (iso and udf) or
+		 * eventually 0 (fat32 boot sector, ext2 superblock, etc), disc
+		 * is assumed non-blank */
+		result = 0;
+
+		for (block = 32768; block >= 0 && !result; block -= 32768) {
+			offset = block;
+			while (offset < (block + 2048) && !result) {
+				result = buffer [offset];
+				offset++;
+			}
+		}
+
+		if (!result) {
+			cd_media_state = media_status[0];
+			info(udev, "no data in blocks 0 or 16, assuming blank\n");
+		} else {
+			info(udev, "data in blocks 0 or 16, assuming complete\n");
+		}
+	}
+
+determined:
 	if ((header[2] & 3) != 2)
 		cd_media_session_next = header[10] << 8 | header[5];
 	cd_media_session_count = header[9] << 8 | header[4];