kernel / Documentation / userspace-api / ioctl / cdrom.rst

============================
Summary of CDROM ioctl calls
============================

- Edward A. Falk <[e-mail]>

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.