Summary of CDROM ioctl calls¶
Edward A. Falk <efalk@google.com>
November, 2004
This document attempts to describe the ioctl(2) calls supported by the CDROM layer. These are by-and-large implemented (as of Linux 2.6) in drivers/cdrom/cdrom.c and drivers/block/scsi_ioctl.c
ioctl values are listed in <linux/cdrom.h>. As of this writing, they are as follows:
CDROMPAUSE
Pause Audio Operation
CDROMRESUME
Resume paused Audio Operation
CDROMPLAYMSF
Play Audio MSF (struct cdrom_msf)
CDROMPLAYTRKIND
Play Audio Track/index (struct cdrom_ti)
CDROMREADTOCHDR
Read TOC header (struct cdrom_tochdr)
CDROMREADTOCENTRY
Read TOC entry (struct cdrom_tocentry)
CDROMSTOP
Stop the cdrom drive
CDROMSTART
Start the cdrom drive
CDROMEJECT
Ejects the cdrom media
CDROMVOLCTRL
Control output volume (struct cdrom_volctrl)
CDROMSUBCHNL
Read subchannel data (struct cdrom_subchnl)
CDROMREADMODE2
Read CDROM mode 2 data (2336 Bytes) (struct cdrom_read)
CDROMREADMODE1
Read CDROM mode 1 data (2048 Bytes) (struct cdrom_read)
CDROMREADAUDIO
(struct cdrom_read_audio)
CDROMEJECT_SW
enable(1)/disable(0) auto-ejecting
CDROMMULTISESSION
Obtain the start-of-last-session address of multi session disks (struct cdrom_multisession)
CDROM_GET_MCN
Obtain the "Universal Product Code" if available (struct cdrom_mcn)
CDROM_GET_UPC
Deprecated, use CDROM_GET_MCN instead.
CDROMRESET
hard-reset the drive
CDROMVOLREAD
Get the drive's volume setting (struct cdrom_volctrl)
CDROMREADRAW
read data in raw mode (2352 Bytes) (struct cdrom_read)
CDROMREADCOOKED
read data in cooked mode
CDROMSEEK
seek msf address
CDROMPLAYBLK
scsi-cd only, (struct cdrom_blk)
CDROMREADALL
read all 2646 bytes
CDROMGETSPINDOWN
return 4-bit spindown value
CDROMSETSPINDOWN
set 4-bit spindown value
CDROMCLOSETRAY
pendant of CDROMEJECT
CDROM_SET_OPTIONS
Set behavior options
CDROM_CLEAR_OPTIONS
Clear behavior options
CDROM_SELECT_SPEED
Set the CD-ROM speed
CDROM_SELECT_DISC
Select disc (for juke-boxes)
CDROM_MEDIA_CHANGED
Check is media changed
CDROM_TIMED_MEDIA_CHANGE
Check if media changed since given time (struct cdrom_timed_media_change_info)
CDROM_DRIVE_STATUS
Get tray position, etc.
CDROM_DISC_STATUS
Get disc type, etc.
CDROM_CHANGER_NSLOTS
Get number of slots
CDROM_LOCKDOOR
lock or unlock door
CDROM_DEBUG
Turn debug messages on/off
CDROM_GET_CAPABILITY
get capabilities
CDROMAUDIOBUFSIZ
set the audio buffer size
DVD_READ_STRUCT
Read structure
DVD_WRITE_STRUCT
Write structure
DVD_AUTH
Authentication
CDROM_SEND_PACKET
send a packet to the drive
CDROM_NEXT_WRITABLE
get next writable block
CDROM_LAST_WRITTEN
get last block written on disc
The information that follows was determined from reading kernel source code. It is likely that some corrections will be made over time.
General:
Unless otherwise specified, all ioctl calls return 0 on success and -1 with errno set to an appropriate value on error. (Some ioctls return non-negative data values.)
Unless otherwise specified, all ioctl calls return -1 and set errno to EFAULT on a failed attempt to copy data to or from user address space.
Individual drivers may return error codes not listed here.
Unless otherwise specified, all data structures and constants are defined in <linux/cdrom.h>
- CDROMPAUSE
Pause Audio Operation
usage:
ioctl(fd, CDROMPAUSE, 0);
- inputs:
none
- outputs:
none
- error return:
ENOSYS cd drive not audio-capable.
- CDROMRESUME
Resume paused Audio Operation
usage:
ioctl(fd, CDROMRESUME, 0);
- inputs:
none
- outputs:
none
- error return:
ENOSYS cd drive not audio-capable.
- CDROMPLAYMSF
Play Audio MSF
(struct cdrom_msf)
usage:
struct cdrom_msf msf; ioctl(fd, CDROMPLAYMSF, &msf);
- inputs:
cdrom_msf structure, describing a segment of music to play
- outputs:
none
- error return:
ENOSYS cd drive not audio-capable.
- notes:
MSF stands for minutes-seconds-frames
LBA stands for logical block address
Segment is described as start and end times, where each time is described as minutes:seconds:frames. A frame is 1/75 of a second.
- CDROMPLAYTRKIND
Play Audio Track/index
(struct cdrom_ti)
usage:
struct cdrom_ti ti; ioctl(fd, CDROMPLAYTRKIND, &ti);
- inputs:
cdrom_ti structure, describing a segment of music to play
- outputs:
none
- error return:
ENOSYS cd drive not audio-capable.
- notes:
Segment is described as start and end times, where each time is described as a track and an index.
- CDROMREADTOCHDR
Read TOC header
(struct cdrom_tochdr)
usage:
cdrom_tochdr header; ioctl(fd, CDROMREADTOCHDR, &header);
- inputs:
cdrom_tochdr structure
- outputs:
cdrom_tochdr structure
- error return:
ENOSYS cd drive not audio-capable.
- CDROMREADTOCENTRY
Read TOC entry
(struct cdrom_tocentry)
usage:
struct cdrom_tocentry entry; ioctl(fd, CDROMREADTOCENTRY, &entry);
- inputs:
cdrom_tocentry structure
- outputs:
cdrom_tocentry structure
- error return:
ENOSYS cd drive not audio-capable.
EINVAL entry.cdte_format not CDROM_MSF or CDROM_LBA
EINVAL requested track out of bounds
EIO I/O error reading TOC
- notes:
TOC stands for Table Of Contents
MSF stands for minutes-seconds-frames
LBA stands for logical block address
- CDROMSTOP
Stop the cdrom drive
usage:
ioctl(fd, CDROMSTOP, 0);
- inputs:
none
- outputs:
none
- error return:
ENOSYS cd drive not audio-capable.
- notes:
Exact interpretation of this ioctl depends on the device, but most seem to spin the drive down.
- CDROMSTART
Start the cdrom drive
usage:
ioctl(fd, CDROMSTART, 0);
- inputs:
none
- outputs:
none
- error return:
ENOSYS cd drive not audio-capable.
- notes:
Exact interpretation of this ioctl depends on the device, but most seem to spin the drive up and/or close the tray. Other devices ignore the ioctl completely.
- CDROMEJECT
Ejects the cdrom media
usage:
ioctl(fd, CDROMEJECT, 0);
- inputs:
none
- outputs:
none
- error returns:
ENOSYS cd drive not capable of ejecting
EBUSY other processes are accessing drive, or door is locked
- notes:
See CDROM_LOCKDOOR, below.
- CDROMCLOSETRAY
pendant of CDROMEJECT
usage:
ioctl(fd, CDROMCLOSETRAY, 0);
- inputs:
none
- outputs:
none
- error returns:
ENOSYS cd drive not capable of closing the tray
EBUSY other processes are accessing drive, or door is locked
- notes:
See CDROM_LOCKDOOR, below.
- CDROMVOLCTRL
Control output volume (struct cdrom_volctrl)
usage:
struct cdrom_volctrl volume; ioctl(fd, CDROMVOLCTRL, &volume);
- inputs:
cdrom_volctrl structure containing volumes for up to 4 channels.
- outputs:
none
- error return:
ENOSYS cd drive not audio-capable.
- CDROMVOLREAD
Get the drive's volume setting
(struct cdrom_volctrl)
usage:
struct cdrom_volctrl volume; ioctl(fd, CDROMVOLREAD, &volume);
- inputs:
none
- outputs:
The current volume settings.
- error return:
ENOSYS cd drive not audio-capable.
- CDROMSUBCHNL
Read subchannel data
(struct cdrom_subchnl)
usage:
struct cdrom_subchnl q; ioctl(fd, CDROMSUBCHNL, &q);
- inputs:
cdrom_subchnl structure
- outputs:
cdrom_subchnl structure
- error return:
ENOSYS cd drive not audio-capable.
EINVAL format not CDROM_MSF or CDROM_LBA
- notes:
Format is converted to CDROM_MSF or CDROM_LBA as per user request on return
- CDROMREADRAW
read data in raw mode (2352 Bytes)
(struct cdrom_read)
usage:
union { struct cdrom_msf msf; /* input */ char buffer[CD_FRAMESIZE_RAW]; /* return */ } arg; ioctl(fd, CDROMREADRAW, &arg);
- inputs:
cdrom_msf structure indicating an address to read.
Only the start values are significant.
- outputs:
Data written to address provided by user.
- error return:
EINVAL address less than 0, or msf less than 0:2:0
ENOMEM out of memory
- notes:
As of 2.6.8.1, comments in <linux/cdrom.h> indicate that this ioctl accepts a cdrom_read structure, but actual source code reads a cdrom_msf structure and writes a buffer of data to the same address.
MSF values are converted to LBA values via this formula:
lba = (((m * CD_SECS) + s) * CD_FRAMES + f) - CD_MSF_OFFSET;
- CDROMREADMODE1
Read CDROM mode 1 data (2048 Bytes)
(struct cdrom_read)
- notes:
Identical to CDROMREADRAW except that block size is CD_FRAMESIZE (2048) bytes
- CDROMREADMODE2
Read CDROM mode 2 data (2336 Bytes)
(struct cdrom_read)
- notes:
Identical to CDROMREADRAW except that block size is CD_FRAMESIZE_RAW0 (2336) bytes
- CDROMREADAUDIO
(struct cdrom_read_audio)
usage:
struct cdrom_read_audio ra; ioctl(fd, CDROMREADAUDIO, &ra);
- inputs:
cdrom_read_audio structure containing read start point and length
- outputs:
audio data, returned to buffer indicated by ra
- error return:
EINVAL format not CDROM_MSF or CDROM_LBA
EINVAL nframes not in range [1 75]
ENXIO drive has no queue (probably means invalid fd)
ENOMEM out of memory
- CDROMEJECT_SW
enable(1)/disable(0) auto-ejecting
usage:
int val; ioctl(fd, CDROMEJECT_SW, val);
- inputs:
Flag specifying auto-eject flag.
- outputs:
none
- error return:
ENOSYS Drive is not capable of ejecting.
EBUSY Door is locked
- CDROMMULTISESSION
Obtain the start-of-last-session address of multi session disks
(struct cdrom_multisession)
usage:
struct cdrom_multisession ms_info; ioctl(fd, CDROMMULTISESSION, &ms_info);
- inputs:
cdrom_multisession structure containing desired
format.
- outputs:
cdrom_multisession structure is filled with last_session information.
- error return:
EINVAL format not CDROM_MSF or CDROM_LBA
- CDROM_GET_MCN
Obtain the "Universal Product Code" if available
(struct cdrom_mcn)
usage:
struct cdrom_mcn mcn; ioctl(fd, CDROM_GET_MCN, &mcn);
- inputs:
none
- outputs:
Universal Product Code
- error return:
ENOSYS Drive is not capable of reading MCN data.
- notes:
Source code comments state:
The following function is implemented, although very few audio discs give Universal Product Code information, which should just be the Medium Catalog Number on the box. Note, that the way the code is written on the CD is /not/ uniform across all discs!
- CDROM_GET_UPC
CDROM_GET_MCN (deprecated)
Not implemented, as of 2.6.8.1
- CDROMRESET
hard-reset the drive
usage:
ioctl(fd, CDROMRESET, 0);
- inputs:
none
- outputs:
none
- error return:
EACCES Access denied: requires CAP_SYS_ADMIN
ENOSYS Drive is not capable of resetting.
- CDROMREADCOOKED
read data in cooked mode
usage:
u8 buffer[CD_FRAMESIZE] ioctl(fd, CDROMREADCOOKED, buffer);
- inputs:
none
- outputs:
2048 bytes of data, "cooked" mode.
- notes:
Not implemented on all drives.
- CDROMREADALL
read all 2646 bytes
Same as CDROMREADCOOKED, but reads 2646 bytes.
- CDROMSEEK
seek msf address
usage:
struct cdrom_msf msf; ioctl(fd, CDROMSEEK, &msf);
- inputs:
MSF address to seek to.
- outputs:
none
- CDROMPLAYBLK
scsi-cd only
(struct cdrom_blk)
usage:
struct cdrom_blk blk; ioctl(fd, CDROMPLAYBLK, &blk);
- inputs:
Region to play
- outputs:
none
- CDROMGETSPINDOWN
Obsolete, was ide-cd only
usage:
char spindown; ioctl(fd, CDROMGETSPINDOWN, &spindown);
- inputs:
none
- outputs:
The value of the current 4-bit spindown value.
- CDROMSETSPINDOWN
Obsolete, was ide-cd only
usage:
char spindown ioctl(fd, CDROMSETSPINDOWN, &spindown);
- inputs:
4-bit value used to control spindown (TODO: more detail here)
- outputs:
none
- CDROM_SET_OPTIONS
Set behavior options
usage:
int options; ioctl(fd, CDROM_SET_OPTIONS, options);
- inputs:
New values for drive options. The logical 'or' of:
CDO_AUTO_CLOSE
close tray on first open(2)
CDO_AUTO_EJECT
open tray on last release
CDO_USE_FFLAGS
use O_NONBLOCK information on open
CDO_LOCK
lock tray on open files
CDO_CHECK_TYPE
check type on open for data
- outputs:
Returns the resulting options settings in the ioctl return value. Returns -1 on error.
- error return:
ENOSYS selected option(s) not supported by drive.
- CDROM_CLEAR_OPTIONS
Clear behavior options
Same as CDROM_SET_OPTIONS, except that selected options are turned off.
- CDROM_SELECT_SPEED
Set the CD-ROM speed
usage:
int speed; ioctl(fd, CDROM_SELECT_SPEED, speed);
- inputs:
New drive speed.
- outputs:
none
- error return:
ENOSYS speed selection not supported by drive.
- CDROM_SELECT_DISC
Select disc (for juke-boxes)
usage:
int disk; ioctl(fd, CDROM_SELECT_DISC, disk);
- inputs:
Disk to load into drive.
- outputs:
none
- error return:
EINVAL Disk number beyond capacity of drive
- CDROM_MEDIA_CHANGED
Check is media changed
usage:
int slot; ioctl(fd, CDROM_MEDIA_CHANGED, slot);
- inputs:
Slot number to be tested, always zero except for jukeboxes.
May also be special values CDSL_NONE or CDSL_CURRENT
- outputs:
Ioctl return value is 0 or 1 depending on whether the media
has been changed, or -1 on error.
- error returns:
ENOSYS Drive can't detect media change
EINVAL Slot number beyond capacity of drive
ENOMEM Out of memory
- CDROM_DRIVE_STATUS
Get tray position, etc.
usage:
int slot; ioctl(fd, CDROM_DRIVE_STATUS, slot);
- inputs:
Slot number to be tested, always zero except for jukeboxes.
May also be special values CDSL_NONE or CDSL_CURRENT
- outputs:
Ioctl return value will be one of the following values
from <linux/cdrom.h>:
CDS_NO_INFO
Information not available.
CDS_NO_DISC
CDS_TRAY_OPEN
CDS_DRIVE_NOT_READY
CDS_DISC_OK
-1
error
- error returns:
ENOSYS Drive can't detect drive status
EINVAL Slot number beyond capacity of drive
ENOMEM Out of memory
- CDROM_DISC_STATUS
Get disc type, etc.
usage:
ioctl(fd, CDROM_DISC_STATUS, 0);
- inputs:
none
- outputs:
Ioctl return value will be one of the following values
from <linux/cdrom.h>:
CDS_NO_INFO
CDS_AUDIO
CDS_MIXED
CDS_XA_2_2
CDS_XA_2_1
CDS_DATA_1
- error returns:
none at present
- notes:
Source code comments state:
Ok, this is where problems start. The current interface for the CDROM_DISC_STATUS ioctl is flawed. It makes the false assumption that CDs are all CDS_DATA_1 or all CDS_AUDIO, etc. Unfortunately, while this is often the case, it is also very common for CDs to have some tracks with data, and some tracks with audio. Just because I feel like it, I declare the following to be the best way to cope. If the CD has ANY data tracks on it, it will be returned as a data CD. If it has any XA tracks, I will return it as that. Now I could simplify this interface by combining these returns with the above, but this more clearly demonstrates the problem with the current interface. Too bad this wasn't designed to use bitmasks... -Erik Well, now we have the option CDS_MIXED: a mixed-type CD. User level programmers might feel the ioctl is not very useful. ---david
- CDROM_CHANGER_NSLOTS
Get number of slots
usage:
ioctl(fd, CDROM_CHANGER_NSLOTS, 0);
- inputs:
none
- outputs:
The ioctl return value will be the number of slots in a CD changer. Typically 1 for non-multi-disk devices.
- error returns:
none
- CDROM_LOCKDOOR
lock or unlock door
usage:
int lock; ioctl(fd, CDROM_LOCKDOOR, lock);
- inputs:
Door lock flag, 1=lock, 0=unlock
- outputs:
none
- error returns:
EDRIVE_CANT_DO_THIS
Door lock function not supported.
EBUSY
Attempt to unlock when multiple users have the drive open and not CAP_SYS_ADMIN
- notes:
As of 2.6.8.1, the lock flag is a global lock, meaning that all CD drives will be locked or unlocked together. This is probably a bug.
The EDRIVE_CANT_DO_THIS value is defined in <linux/cdrom.h> and is currently (2.6.8.1) the same as EOPNOTSUPP
- CDROM_DEBUG
Turn debug messages on/off
usage:
int debug; ioctl(fd, CDROM_DEBUG, debug);
- inputs:
Cdrom debug flag, 0=disable, 1=enable
- outputs:
The ioctl return value will be the new debug flag.
- error return:
EACCES Access denied: requires CAP_SYS_ADMIN
- CDROM_GET_CAPABILITY
get capabilities
usage:
ioctl(fd, CDROM_GET_CAPABILITY, 0);
- inputs:
none
- outputs:
The ioctl return value is the current device capability flags. See CDC_CLOSE_TRAY, CDC_OPEN_TRAY, etc.
- CDROMAUDIOBUFSIZ
set the audio buffer size
usage:
int arg; ioctl(fd, CDROMAUDIOBUFSIZ, val);
- inputs:
New audio buffer size
- outputs:
The ioctl return value is the new audio buffer size, or -1 on error.
- error return:
ENOSYS Not supported by this driver.
- notes:
Not supported by all drivers.
DVD_READ_STRUCT Read structure
usage:
dvd_struct s; ioctl(fd, DVD_READ_STRUCT, &s);
- inputs:
dvd_struct structure, containing:
type
specifies the information desired, one of DVD_STRUCT_PHYSICAL, DVD_STRUCT_COPYRIGHT, DVD_STRUCT_DISCKEY, DVD_STRUCT_BCA, DVD_STRUCT_MANUFACT
physical.layer_num
desired layer, indexed from 0
copyright.layer_num
desired layer, indexed from 0
disckey.agid
- outputs:
dvd_struct structure, containing:
physical
for type == DVD_STRUCT_PHYSICAL
copyright
for type == DVD_STRUCT_COPYRIGHT
disckey.value
for type == DVD_STRUCT_DISCKEY
bca.{len,value}
for type == DVD_STRUCT_BCA
manufact.{len,valu}
for type == DVD_STRUCT_MANUFACT
- error returns:
EINVAL physical.layer_num exceeds number of layers
EIO Received invalid response from drive
DVD_WRITE_STRUCT Write structure
Not implemented, as of 2.6.8.1
DVD_AUTH Authentication
usage:
dvd_authinfo ai; ioctl(fd, DVD_AUTH, &ai);
- inputs:
dvd_authinfo structure. See <linux/cdrom.h>
- outputs:
dvd_authinfo structure.
- error return:
ENOTTY ai.type not recognized.
- CDROM_SEND_PACKET
send a packet to the drive
usage:
struct cdrom_generic_command cgc; ioctl(fd, CDROM_SEND_PACKET, &cgc);
- inputs:
cdrom_generic_command structure containing the packet to send.
- outputs:
none
cdrom_generic_command structure containing results.
- error return:
EIO
command failed.
EPERM
Operation not permitted, either because a write command was attempted on a drive which is opened read-only, or because the command requires CAP_SYS_RAWIO
EINVAL
cgc.data_direction not set
- CDROM_NEXT_WRITABLE
get next writable block
usage:
long next; ioctl(fd, CDROM_NEXT_WRITABLE, &next);
- inputs:
none
- outputs:
The next writable block.
- notes:
If the device does not support this ioctl directly, the
ioctl will return CDROM_LAST_WRITTEN + 7.
- CDROM_LAST_WRITTEN
get last block written on disc
usage:
long last; ioctl(fd, CDROM_LAST_WRITTEN, &last);
- inputs:
none
- outputs:
The last block written on disc
- notes:
If the device does not support this ioctl directly, the result is derived from the disc's table of contents. If the table of contents can't be read, this ioctl returns an error.