cdrom.txt

linux 内核源代码

		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_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, 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.



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 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!