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+                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, 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!
+
+
+
+
+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.
+            Unfortunatly, 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           Recieved 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.