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_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 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 usage: char spindown; ioctl(fd, CDROMGETSPINDOWN, &spindown); inputs: none outputs: The value of the current 4-bit spindown value. CDROMSETSPINDOWN 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.