| blob | 3b4c0506de466a362bc4c9d686cdc2e4462b422e |
1 ============================
2 Summary of CDROM ioctl calls
3 ============================
5 - Edward A. Falk <efalk@google.com>
7 November, 2004
9 This document attempts to describe the ioctl(2) calls supported by
10 the CDROM layer. These are by-and-large implemented (as of Linux 2.6)
11 in drivers/cdrom/cdrom.c and drivers/block/scsi_ioctl.c
13 ioctl values are listed in <linux/cdrom.h>. As of this writing, they
14 are as follows:
16 ====================== ===============================================
17 CDROMPAUSE Pause Audio Operation
18 CDROMRESUME Resume paused Audio Operation
19 CDROMPLAYMSF Play Audio MSF (struct cdrom_msf)
20 CDROMPLAYTRKIND Play Audio Track/index (struct cdrom_ti)
21 CDROMREADTOCHDR Read TOC header (struct cdrom_tochdr)
22 CDROMREADTOCENTRY Read TOC entry (struct cdrom_tocentry)
23 CDROMSTOP Stop the cdrom drive
24 CDROMSTART Start the cdrom drive
25 CDROMEJECT Ejects the cdrom media
26 CDROMVOLCTRL Control output volume (struct cdrom_volctrl)
27 CDROMSUBCHNL Read subchannel data (struct cdrom_subchnl)
28 CDROMREADMODE2 Read CDROM mode 2 data (2336 Bytes)
29 (struct cdrom_read)
30 CDROMREADMODE1 Read CDROM mode 1 data (2048 Bytes)
31 (struct cdrom_read)
32 CDROMREADAUDIO (struct cdrom_read_audio)
33 CDROMEJECT_SW enable(1)/disable(0) auto-ejecting
34 CDROMMULTISESSION Obtain the start-of-last-session
35 address of multi session disks
36 (struct cdrom_multisession)
37 CDROM_GET_MCN Obtain the "Universal Product Code"
38 if available (struct cdrom_mcn)
39 CDROM_GET_UPC Deprecated, use CDROM_GET_MCN instead.
40 CDROMRESET hard-reset the drive
41 CDROMVOLREAD Get the drive's volume setting
42 (struct cdrom_volctrl)
43 CDROMREADRAW read data in raw mode (2352 Bytes)
44 (struct cdrom_read)
45 CDROMREADCOOKED read data in cooked mode
46 CDROMSEEK seek msf address
47 CDROMPLAYBLK scsi-cd only, (struct cdrom_blk)
48 CDROMREADALL read all 2646 bytes
49 CDROMGETSPINDOWN return 4-bit spindown value
50 CDROMSETSPINDOWN set 4-bit spindown value
51 CDROMCLOSETRAY pendant of CDROMEJECT
52 CDROM_SET_OPTIONS Set behavior options
53 CDROM_CLEAR_OPTIONS Clear behavior options
54 CDROM_SELECT_SPEED Set the CD-ROM speed
55 CDROM_SELECT_DISC Select disc (for juke-boxes)
56 CDROM_MEDIA_CHANGED Check is media changed
57 CDROM_DRIVE_STATUS Get tray position, etc.
58 CDROM_DISC_STATUS Get disc type, etc.
59 CDROM_CHANGER_NSLOTS Get number of slots
60 CDROM_LOCKDOOR lock or unlock door
61 CDROM_DEBUG Turn debug messages on/off
62 CDROM_GET_CAPABILITY get capabilities
63 CDROMAUDIOBUFSIZ set the audio buffer size
64 DVD_READ_STRUCT Read structure
65 DVD_WRITE_STRUCT Write structure
66 DVD_AUTH Authentication
67 CDROM_SEND_PACKET send a packet to the drive
68 CDROM_NEXT_WRITABLE get next writable block
69 CDROM_LAST_WRITTEN get last block written on disc
70 ====================== ===============================================
73 The information that follows was determined from reading kernel source
74 code. It is likely that some corrections will be made over time.
76 ------------------------------------------------------------------------------
78 General:
80 Unless otherwise specified, all ioctl calls return 0 on success
81 and -1 with errno set to an appropriate value on error. (Some
82 ioctls return non-negative data values.)
84 Unless otherwise specified, all ioctl calls return -1 and set
85 errno to EFAULT on a failed attempt to copy data to or from user
86 address space.
88 Individual drivers may return error codes not listed here.
90 Unless otherwise specified, all data structures and constants
91 are defined in <linux/cdrom.h>
93 ------------------------------------------------------------------------------
96 CDROMPAUSE
97 Pause Audio Operation
100 usage::
102 ioctl(fd, CDROMPAUSE, 0);
105 inputs:
106 none
109 outputs:
110 none
113 error return:
114 - ENOSYS cd drive not audio-capable.
117 CDROMRESUME
118 Resume paused Audio Operation
121 usage::
123 ioctl(fd, CDROMRESUME, 0);
126 inputs:
127 none
130 outputs:
131 none
134 error return:
135 - ENOSYS cd drive not audio-capable.
138 CDROMPLAYMSF
139 Play Audio MSF
141 (struct cdrom_msf)
144 usage::
146 struct cdrom_msf msf;
148 ioctl(fd, CDROMPLAYMSF, &msf);
150 inputs:
151 cdrom_msf structure, describing a segment of music to play
154 outputs:
155 none
158 error return:
159 - ENOSYS cd drive not audio-capable.
161 notes:
162 - MSF stands for minutes-seconds-frames
163 - LBA stands for logical block address
164 - Segment is described as start and end times, where each time
165 is described as minutes:seconds:frames.
166 A frame is 1/75 of a second.
169 CDROMPLAYTRKIND
170 Play Audio Track/index
172 (struct cdrom_ti)
175 usage::
177 struct cdrom_ti ti;
179 ioctl(fd, CDROMPLAYTRKIND, &ti);
181 inputs:
182 cdrom_ti structure, describing a segment of music to play
185 outputs:
186 none
189 error return:
190 - ENOSYS cd drive not audio-capable.
192 notes:
193 - Segment is described as start and end times, where each time
194 is described as a track and an index.
198 CDROMREADTOCHDR
199 Read TOC header
201 (struct cdrom_tochdr)
204 usage::
206 cdrom_tochdr header;
208 ioctl(fd, CDROMREADTOCHDR, &header);
210 inputs:
211 cdrom_tochdr structure
214 outputs:
215 cdrom_tochdr structure
218 error return:
219 - ENOSYS cd drive not audio-capable.
223 CDROMREADTOCENTRY
224 Read TOC entry
226 (struct cdrom_tocentry)
229 usage::
231 struct cdrom_tocentry entry;
233 ioctl(fd, CDROMREADTOCENTRY, &entry);
235 inputs:
236 cdrom_tocentry structure
239 outputs:
240 cdrom_tocentry structure
243 error return:
244 - ENOSYS cd drive not audio-capable.
245 - EINVAL entry.cdte_format not CDROM_MSF or CDROM_LBA
246 - EINVAL requested track out of bounds
247 - EIO I/O error reading TOC
249 notes:
250 - TOC stands for Table Of Contents
251 - MSF stands for minutes-seconds-frames
252 - LBA stands for logical block address
256 CDROMSTOP
257 Stop the cdrom drive
260 usage::
262 ioctl(fd, CDROMSTOP, 0);
265 inputs:
266 none
269 outputs:
270 none
273 error return:
274 - ENOSYS cd drive not audio-capable.
276 notes:
277 - Exact interpretation of this ioctl depends on the device,
278 but most seem to spin the drive down.
281 CDROMSTART
282 Start the cdrom drive
285 usage::
287 ioctl(fd, CDROMSTART, 0);
290 inputs:
291 none
294 outputs:
295 none
298 error return:
299 - ENOSYS cd drive not audio-capable.
301 notes:
302 - Exact interpretation of this ioctl depends on the device,
303 but most seem to spin the drive up and/or close the tray.
304 Other devices ignore the ioctl completely.
307 CDROMEJECT
308 - Ejects the cdrom media
311 usage::
313 ioctl(fd, CDROMEJECT, 0);
316 inputs:
317 none
320 outputs:
321 none
324 error returns:
325 - ENOSYS cd drive not capable of ejecting
326 - EBUSY other processes are accessing drive, or door is locked
328 notes:
329 - See CDROM_LOCKDOOR, below.
334 CDROMCLOSETRAY
335 pendant of CDROMEJECT
338 usage::
340 ioctl(fd, CDROMCLOSETRAY, 0);
343 inputs:
344 none
347 outputs:
348 none
351 error returns:
352 - ENOSYS cd drive not capable of closing the tray
353 - EBUSY other processes are accessing drive, or door is locked
355 notes:
356 - See CDROM_LOCKDOOR, below.
361 CDROMVOLCTRL
362 Control output volume (struct cdrom_volctrl)
365 usage::
367 struct cdrom_volctrl volume;
369 ioctl(fd, CDROMVOLCTRL, &volume);
371 inputs:
372 cdrom_volctrl structure containing volumes for up to 4
373 channels.
375 outputs:
376 none
379 error return:
380 - ENOSYS cd drive not audio-capable.
384 CDROMVOLREAD
385 Get the drive's volume setting
387 (struct cdrom_volctrl)
390 usage::
392 struct cdrom_volctrl volume;
394 ioctl(fd, CDROMVOLREAD, &volume);
396 inputs:
397 none
400 outputs:
401 The current volume settings.
404 error return:
405 - ENOSYS cd drive not audio-capable.
409 CDROMSUBCHNL
410 Read subchannel data
412 (struct cdrom_subchnl)
415 usage::
417 struct cdrom_subchnl q;
419 ioctl(fd, CDROMSUBCHNL, &q);
421 inputs:
422 cdrom_subchnl structure
425 outputs:
426 cdrom_subchnl structure
429 error return:
430 - ENOSYS cd drive not audio-capable.
431 - EINVAL format not CDROM_MSF or CDROM_LBA
433 notes:
434 - Format is converted to CDROM_MSF or CDROM_LBA
435 as per user request on return
439 CDROMREADRAW
440 read data in raw mode (2352 Bytes)
442 (struct cdrom_read)
444 usage::
446 union {
448 struct cdrom_msf msf; /* input */
449 char buffer[CD_FRAMESIZE_RAW]; /* return */
450 } arg;
451 ioctl(fd, CDROMREADRAW, &arg);
453 inputs:
454 cdrom_msf structure indicating an address to read.
456 Only the start values are significant.
458 outputs:
459 Data written to address provided by user.
462 error return:
463 - EINVAL address less than 0, or msf less than 0:2:0
464 - ENOMEM out of memory
466 notes:
467 - As of 2.6.8.1, comments in <linux/cdrom.h> indicate that this
468 ioctl accepts a cdrom_read structure, but actual source code
469 reads a cdrom_msf structure and writes a buffer of data to
470 the same address.
472 - MSF values are converted to LBA values via this formula::
474 lba = (((m * CD_SECS) + s) * CD_FRAMES + f) - CD_MSF_OFFSET;
479 CDROMREADMODE1
480 Read CDROM mode 1 data (2048 Bytes)
482 (struct cdrom_read)
484 notes:
485 Identical to CDROMREADRAW except that block size is
486 CD_FRAMESIZE (2048) bytes
490 CDROMREADMODE2
491 Read CDROM mode 2 data (2336 Bytes)
493 (struct cdrom_read)
495 notes:
496 Identical to CDROMREADRAW except that block size is
497 CD_FRAMESIZE_RAW0 (2336) bytes
501 CDROMREADAUDIO
502 (struct cdrom_read_audio)
504 usage::
506 struct cdrom_read_audio ra;
508 ioctl(fd, CDROMREADAUDIO, &ra);
510 inputs:
511 cdrom_read_audio structure containing read start
512 point and length
514 outputs:
515 audio data, returned to buffer indicated by ra
518 error return:
519 - EINVAL format not CDROM_MSF or CDROM_LBA
520 - EINVAL nframes not in range [1 75]
521 - ENXIO drive has no queue (probably means invalid fd)
522 - ENOMEM out of memory
525 CDROMEJECT_SW
526 enable(1)/disable(0) auto-ejecting
529 usage::
531 int val;
533 ioctl(fd, CDROMEJECT_SW, val);
535 inputs:
536 Flag specifying auto-eject flag.
539 outputs:
540 none
543 error return:
544 - ENOSYS Drive is not capable of ejecting.
545 - EBUSY Door is locked
550 CDROMMULTISESSION
551 Obtain the start-of-last-session address of multi session disks
553 (struct cdrom_multisession)
555 usage::
557 struct cdrom_multisession ms_info;
559 ioctl(fd, CDROMMULTISESSION, &ms_info);
561 inputs:
562 cdrom_multisession structure containing desired
564 format.
566 outputs:
567 cdrom_multisession structure is filled with last_session
568 information.
570 error return:
571 - EINVAL format not CDROM_MSF or CDROM_LBA
574 CDROM_GET_MCN
575 Obtain the "Universal Product Code"
576 if available
578 (struct cdrom_mcn)
581 usage::
583 struct cdrom_mcn mcn;
585 ioctl(fd, CDROM_GET_MCN, &mcn);
587 inputs:
588 none
591 outputs:
592 Universal Product Code
595 error return:
596 - ENOSYS Drive is not capable of reading MCN data.
598 notes:
599 - Source code comments state::
601 The following function is implemented, although very few
602 audio discs give Universal Product Code information, which
603 should just be the Medium Catalog Number on the box. Note,
604 that the way the code is written on the CD is /not/ uniform
605 across all discs!
610 CDROM_GET_UPC
611 CDROM_GET_MCN (deprecated)
614 Not implemented, as of 2.6.8.1
618 CDROMRESET
619 hard-reset the drive
622 usage::
624 ioctl(fd, CDROMRESET, 0);
627 inputs:
628 none
631 outputs:
632 none
635 error return:
636 - EACCES Access denied: requires CAP_SYS_ADMIN
637 - ENOSYS Drive is not capable of resetting.
642 CDROMREADCOOKED
643 read data in cooked mode
646 usage::
648 u8 buffer[CD_FRAMESIZE]
650 ioctl(fd, CDROMREADCOOKED, buffer);
652 inputs:
653 none
656 outputs:
657 2048 bytes of data, "cooked" mode.
660 notes:
661 Not implemented on all drives.
667 CDROMREADALL
668 read all 2646 bytes
671 Same as CDROMREADCOOKED, but reads 2646 bytes.
675 CDROMSEEK
676 seek msf address
679 usage::
681 struct cdrom_msf msf;
683 ioctl(fd, CDROMSEEK, &msf);
685 inputs:
686 MSF address to seek to.
689 outputs:
690 none
695 CDROMPLAYBLK
696 scsi-cd only
698 (struct cdrom_blk)
701 usage::
703 struct cdrom_blk blk;
705 ioctl(fd, CDROMPLAYBLK, &blk);
707 inputs:
708 Region to play
711 outputs:
712 none
717 CDROMGETSPINDOWN
718 usage::
720 char spindown;
722 ioctl(fd, CDROMGETSPINDOWN, &spindown);
724 inputs:
725 none
728 outputs:
729 The value of the current 4-bit spindown value.
735 CDROMSETSPINDOWN
736 usage::
738 char spindown
740 ioctl(fd, CDROMSETSPINDOWN, &spindown);
742 inputs:
743 4-bit value used to control spindown (TODO: more detail here)
746 outputs:
747 none
754 CDROM_SET_OPTIONS
755 Set behavior options
758 usage::
760 int options;
762 ioctl(fd, CDROM_SET_OPTIONS, options);
764 inputs:
765 New values for drive options. The logical 'or' of:
767 ============== ==================================
768 CDO_AUTO_CLOSE close tray on first open(2)
769 CDO_AUTO_EJECT open tray on last release
770 CDO_USE_FFLAGS use O_NONBLOCK information on open
771 CDO_LOCK lock tray on open files
772 CDO_CHECK_TYPE check type on open for data
773 ============== ==================================
775 outputs:
776 Returns the resulting options settings in the
777 ioctl return value. Returns -1 on error.
779 error return:
780 - ENOSYS selected option(s) not supported by drive.
785 CDROM_CLEAR_OPTIONS
786 Clear behavior options
789 Same as CDROM_SET_OPTIONS, except that selected options are
790 turned off.
794 CDROM_SELECT_SPEED
795 Set the CD-ROM speed
798 usage::
800 int speed;
802 ioctl(fd, CDROM_SELECT_SPEED, speed);
804 inputs:
805 New drive speed.
808 outputs:
809 none
812 error return:
813 - ENOSYS speed selection not supported by drive.
817 CDROM_SELECT_DISC
818 Select disc (for juke-boxes)
821 usage::
823 int disk;
825 ioctl(fd, CDROM_SELECT_DISC, disk);
827 inputs:
828 Disk to load into drive.
831 outputs:
832 none
835 error return:
836 - EINVAL Disk number beyond capacity of drive
840 CDROM_MEDIA_CHANGED
841 Check is media changed
844 usage::
846 int slot;
848 ioctl(fd, CDROM_MEDIA_CHANGED, slot);
850 inputs:
851 Slot number to be tested, always zero except for jukeboxes.
853 May also be special values CDSL_NONE or CDSL_CURRENT
855 outputs:
856 Ioctl return value is 0 or 1 depending on whether the media
858 has been changed, or -1 on error.
860 error returns:
861 - ENOSYS Drive can't detect media change
862 - EINVAL Slot number beyond capacity of drive
863 - ENOMEM Out of memory
867 CDROM_DRIVE_STATUS
868 Get tray position, etc.
871 usage::
873 int slot;
875 ioctl(fd, CDROM_DRIVE_STATUS, slot);
877 inputs:
878 Slot number to be tested, always zero except for jukeboxes.
880 May also be special values CDSL_NONE or CDSL_CURRENT
882 outputs:
883 Ioctl return value will be one of the following values
885 from <linux/cdrom.h>:
887 =================== ==========================
888 CDS_NO_INFO Information not available.
889 CDS_NO_DISC
890 CDS_TRAY_OPEN
891 CDS_DRIVE_NOT_READY
892 CDS_DISC_OK
893 -1 error
894 =================== ==========================
896 error returns:
897 - ENOSYS Drive can't detect drive status
898 - EINVAL Slot number beyond capacity of drive
899 - ENOMEM Out of memory
904 CDROM_DISC_STATUS
905 Get disc type, etc.
908 usage::
910 ioctl(fd, CDROM_DISC_STATUS, 0);
913 inputs:
914 none
917 outputs:
918 Ioctl return value will be one of the following values
920 from <linux/cdrom.h>:
922 - CDS_NO_INFO
923 - CDS_AUDIO
924 - CDS_MIXED
925 - CDS_XA_2_2
926 - CDS_XA_2_1
927 - CDS_DATA_1
929 error returns:
930 none at present
932 notes:
933 - Source code comments state::
936 Ok, this is where problems start. The current interface for
937 the CDROM_DISC_STATUS ioctl is flawed. It makes the false
938 assumption that CDs are all CDS_DATA_1 or all CDS_AUDIO, etc.
939 Unfortunately, while this is often the case, it is also
940 very common for CDs to have some tracks with data, and some
941 tracks with audio. Just because I feel like it, I declare
942 the following to be the best way to cope. If the CD has
943 ANY data tracks on it, it will be returned as a data CD.
944 If it has any XA tracks, I will return it as that. Now I
945 could simplify this interface by combining these returns with
946 the above, but this more clearly demonstrates the problem
947 with the current interface. Too bad this wasn't designed
948 to use bitmasks... -Erik
950 Well, now we have the option CDS_MIXED: a mixed-type CD.
951 User level programmers might feel the ioctl is not very
952 useful.
953 ---david
958 CDROM_CHANGER_NSLOTS
959 Get number of slots
962 usage::
964 ioctl(fd, CDROM_CHANGER_NSLOTS, 0);
967 inputs:
968 none
971 outputs:
972 The ioctl return value will be the number of slots in a
973 CD changer. Typically 1 for non-multi-disk devices.
975 error returns:
976 none
980 CDROM_LOCKDOOR
981 lock or unlock door
984 usage::
986 int lock;
988 ioctl(fd, CDROM_LOCKDOOR, lock);
990 inputs:
991 Door lock flag, 1=lock, 0=unlock
994 outputs:
995 none
998 error returns:
999 - EDRIVE_CANT_DO_THIS
1001 Door lock function not supported.
1002 - EBUSY
1004 Attempt to unlock when multiple users
1005 have the drive open and not CAP_SYS_ADMIN
1007 notes:
1008 As of 2.6.8.1, the lock flag is a global lock, meaning that
1009 all CD drives will be locked or unlocked together. This is
1010 probably a bug.
1012 The EDRIVE_CANT_DO_THIS value is defined in <linux/cdrom.h>
1013 and is currently (2.6.8.1) the same as EOPNOTSUPP
1017 CDROM_DEBUG
1018 Turn debug messages on/off
1021 usage::
1023 int debug;
1025 ioctl(fd, CDROM_DEBUG, debug);
1027 inputs:
1028 Cdrom debug flag, 0=disable, 1=enable
1031 outputs:
1032 The ioctl return value will be the new debug flag.
1035 error return:
1036 - EACCES Access denied: requires CAP_SYS_ADMIN
1040 CDROM_GET_CAPABILITY
1041 get capabilities
1044 usage::
1046 ioctl(fd, CDROM_GET_CAPABILITY, 0);
1049 inputs:
1050 none
1053 outputs:
1054 The ioctl return value is the current device capability
1055 flags. See CDC_CLOSE_TRAY, CDC_OPEN_TRAY, etc.
1059 CDROMAUDIOBUFSIZ
1060 set the audio buffer size
1063 usage::
1065 int arg;
1067 ioctl(fd, CDROMAUDIOBUFSIZ, val);
1069 inputs:
1070 New audio buffer size
1073 outputs:
1074 The ioctl return value is the new audio buffer size, or -1
1075 on error.
1077 error return:
1078 - ENOSYS Not supported by this driver.
1080 notes:
1081 Not supported by all drivers.
1086 DVD_READ_STRUCT Read structure
1088 usage::
1090 dvd_struct s;
1092 ioctl(fd, DVD_READ_STRUCT, &s);
1094 inputs:
1095 dvd_struct structure, containing:
1097 =================== ==========================================
1098 type specifies the information desired, one of
1099 DVD_STRUCT_PHYSICAL, DVD_STRUCT_COPYRIGHT,
1100 DVD_STRUCT_DISCKEY, DVD_STRUCT_BCA,
1101 DVD_STRUCT_MANUFACT
1102 physical.layer_num desired layer, indexed from 0
1103 copyright.layer_num desired layer, indexed from 0
1104 disckey.agid
1105 =================== ==========================================
1107 outputs:
1108 dvd_struct structure, containing:
1110 =================== ================================
1111 physical for type == DVD_STRUCT_PHYSICAL
1112 copyright for type == DVD_STRUCT_COPYRIGHT
1113 disckey.value for type == DVD_STRUCT_DISCKEY
1114 bca.{len,value} for type == DVD_STRUCT_BCA
1115 manufact.{len,valu} for type == DVD_STRUCT_MANUFACT
1116 =================== ================================
1118 error returns:
1119 - EINVAL physical.layer_num exceeds number of layers
1120 - EIO Received invalid response from drive
1124 DVD_WRITE_STRUCT Write structure
1126 Not implemented, as of 2.6.8.1
1130 DVD_AUTH Authentication
1132 usage::
1134 dvd_authinfo ai;
1136 ioctl(fd, DVD_AUTH, &ai);
1138 inputs:
1139 dvd_authinfo structure. See <linux/cdrom.h>
1142 outputs:
1143 dvd_authinfo structure.
1146 error return:
1147 - ENOTTY ai.type not recognized.
1151 CDROM_SEND_PACKET
1152 send a packet to the drive
1155 usage::
1157 struct cdrom_generic_command cgc;
1159 ioctl(fd, CDROM_SEND_PACKET, &cgc);
1161 inputs:
1162 cdrom_generic_command structure containing the packet to send.
1165 outputs:
1166 none
1168 cdrom_generic_command structure containing results.
1170 error return:
1171 - EIO
1173 command failed.
1174 - EPERM
1176 Operation not permitted, either because a
1177 write command was attempted on a drive which
1178 is opened read-only, or because the command
1179 requires CAP_SYS_RAWIO
1180 - EINVAL
1182 cgc.data_direction not set
1186 CDROM_NEXT_WRITABLE
1187 get next writable block
1190 usage::
1192 long next;
1194 ioctl(fd, CDROM_NEXT_WRITABLE, &next);
1196 inputs:
1197 none
1200 outputs:
1201 The next writable block.
1204 notes:
1205 If the device does not support this ioctl directly, the
1207 ioctl will return CDROM_LAST_WRITTEN + 7.
1211 CDROM_LAST_WRITTEN
1212 get last block written on disc
1215 usage::
1217 long last;
1219 ioctl(fd, CDROM_LAST_WRITTEN, &last);
1221 inputs:
1222 none
1225 outputs:
1226 The last block written on disc
1229 notes:
1230 If the device does not support this ioctl directly, the
1231 result is derived from the disc's table of contents. If the
1232 table of contents can't be read, this ioctl returns an
1233 error.