============================
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.