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NAME

     mtio - FreeBSD magtape interface

DESCRIPTION

     The special files named /dev/[n]sa* refer to SCSI tape drives, which may
     be attached to the system.  /dev/[n]sa*.ctl are control devices that can
     be used to issue ioctls to the SCSI tape driver to set parameters that
     are required to last beyond the unmounting of a tape.

     The rewind devices automatically rewind when the last requested read,
     write or seek has finished, or the end of the tape has been reached.  The
     letter ‘n’ is usually prepended to the name of the no-rewind devices.

     Tapes can be written with either fixed length records or variable length
     records.  See sa(4) for more information.  Two end-of-file markers mark
     the end of a tape, and one end-of-file marker marks the end of a tape
     file.  If the tape is not to be rewound it is positioned with the head in
     between the two tape marks, where the next write will over write the
     second end-of-file marker.

     All of the magtape devices may be manipulated with the mt(1) command.

     A number of ioctl(2) operations are available on raw magnetic tape.  The
     following definitions are from

     #ifndef _SYS_MTIO_H_
     #define _SYS_MTIO_H_

     #ifndef _KERNEL
     #include <sys/types.h>
     #endif
     #include <sys/ioccom.h>

     /*
      * Structures and definitions for mag tape io control commands
      */

     /* structure for MTIOCTOP - mag tape op command */
     struct mtop {
             short   mt_op;          /* operations defined below */
             daddr_t mt_count;       /* how many of them */
     };

     /* operations */
     #define MTWEOF          0       /* write an end-of-file record */
     #define MTFSF           1       /* forward space file */
     #define MTBSF           2       /* backward space file */
     #define MTFSR           3       /* forward space record */
     #define MTBSR           4       /* backward space record */
     #define MTREW           5       /* rewind */
     #define MTOFFL          6       /* rewind and put the drive offline */
     #define MTNOP           7       /* no operation, sets status only */
     #define MTCACHE         8       /* enable controller cache */
     #define MTNOCACHE       9       /* disable controller cache */

     #if defined(__FreeBSD__)
     /* Set block size for device. If device is a variable size dev          */
     /* a non zero parameter will change the device to a fixed block size    */
     /* device with block size set to that of the parameter passed in.       */
     /* Resetting the block size to 0 will restore the device to a variable  */
     /* block size device. */

     #define MTSETBSIZ       10

     /* Set density values for device. Sets the value for the opened mode only. */

     #define MTSETDNSTY      11

     #define MTERASE         12      /* erase to EOM */
     #define MTEOD           13      /* Space to EOM */
     #define MTCOMP          14      /* select compression mode 0=off, 1=def */
     #define MTRETENS        15      /* re-tension tape */
     #define MTWSS           16      /* write setmark(s) */
     #define MTFSS           17      /* forward space setmark */
     #define MTBSS           18      /* backward space setmark */

     #define MT_COMP_ENABLE          0xffffffff
     #define MT_COMP_DISABLED        0xfffffffe
     #define MT_COMP_UNSUPP          0xfffffffd

     /*
      * Values in mt_dsreg that say what the device is doing
      */
     #define MTIO_DSREG_NIL  0       /* Unknown */
     #define MTIO_DSREG_REST 1       /* Doing Nothing */
     #define MTIO_DSREG_RBSY 2       /* Communicating with tape (but no motion) */
     #define MTIO_DSREG_WR   20      /* Writing */
     #define MTIO_DSREG_FMK  21      /* Writing Filemarks */
     #define MTIO_DSREG_ZER  22      /* Erasing */
     #define MTIO_DSREG_RD   30      /* Reading */
     #define MTIO_DSREG_FWD  40      /* Spacing Forward */
     #define MTIO_DSREG_REV  41      /* Spacing Reverse */
     #define MTIO_DSREG_POS  42      /* Hardware Positioning (direction unknown) */
     #define MTIO_DSREG_REW  43      /* Rewinding */
     #define MTIO_DSREG_TEN  44      /* Retensioning */
     #define MTIO_DSREG_UNL  45      /* Unloading */
     #define MTIO_DSREG_LD   46      /* Loading */

     #endif  /* __FreeBSD__ */

     /* structure for MTIOCGET - mag tape get status command */

     struct mtget {
             short   mt_type;        /* type of magtape device */
     /* the following two registers are grossly device dependent */
             short   mt_dsreg;       /* ‘‘drive status’’ register */
             short   mt_erreg;       /* ‘‘error’’ register */
     /* end device-dependent registers */
             short   mt_resid;       /* residual count */
     #if defined (__FreeBSD__)
             daddr_t mt_blksiz;      /* presently operating blocksize */
             daddr_t mt_density;     /* presently operating density */
             u_int32_t mt_comp;      /* presently operating compression */
             daddr_t mt_blksiz0;     /* blocksize for mode 0 */
             daddr_t mt_blksiz1;     /* blocksize for mode 1 */
             daddr_t mt_blksiz2;     /* blocksize for mode 2 */
             daddr_t mt_blksiz3;     /* blocksize for mode 3 */
             daddr_t mt_density0;    /* density for mode 0 */
             daddr_t mt_density1;    /* density for mode 1 */
             daddr_t mt_density2;    /* density for mode 2 */
             daddr_t mt_density3;    /* density for mode 3 */
     /* the following are not yet implemented */
             u_int32_t mt_comp0;     /* compression type for mode 0 */
             u_int32_t mt_comp1;     /* compression type for mode 1 */
             u_int32_t mt_comp2;     /* compression type for mode 2 */
             u_int32_t mt_comp3;     /* compression type for mode 3 */
     /* end not yet implemented */
     #endif
             daddr_t mt_fileno;      /* relative file number of current position */
             daddr_t mt_blkno;       /* relative block number of current position */
     };

     /* structure for MTIOCERRSTAT - tape get error status command */
     /* really only supported for SCSI tapes right now */
     struct scsi_tape_errors {
             /*
              * These are latched from the last command that had a SCSI
              * Check Condition noted for these operations. The act
              * of issuing an MTIOCERRSTAT unlatches and clears them.
              */
             u_int8_t io_sense[32];  /* Last Sense Data For Data I/O */
             u_int32_t io_resid;     /* residual count from last Data I/O */
             u_int8_t io_cdb[16];    /* Command that Caused the Last Data Sense */
             u_int8_t ctl_sense[32]; /* Last Sense Data For Control I/O */
             u_int32_t ctl_resid;    /* residual count from last Control I/O */
             u_int8_t ctl_cdb[16];   /* Command that Caused the Last Control Sense */
             /*
              * These are the read and write cumulative error counters.
              * (how to reset cumulative error counters is not yet defined).
              * (not implemented as yet but space is being reserved for them)
              */
             struct {
                     u_int32_t retries;      /* total # retries performed */
                     u_int32_t corrected;    /* total # corrections performed */
                     u_int32_t processed;    /* total # corrections successful */
                     u_int32_t failures;     /* total # corrections/retries failed */
                     u_int64_t nbytes;       /* total # bytes processed */
             } wterr, rderr;
     };

     union mterrstat {
             struct scsi_tape_errors scsi_errstat;
             char _reserved_padding[256];
     };

     /*
      * Constants for mt_type byte.  These are the same
      * for controllers compatible with the types listed.
      */
     #define MT_ISTS         0x01            /* TS-11 */
     #define MT_ISHT         0x02            /* TM03 Massbus: TE16, TU45, TU77 */
     #define MT_ISTM         0x03            /* TM11/TE10 Unibus */
     #define MT_ISMT         0x04            /* TM78/TU78 Massbus */
     #define MT_ISUT         0x05            /* SI TU-45 emulation on Unibus */
     #define MT_ISCPC        0x06            /* SUN */
     #define MT_ISAR         0x07            /* SUN */
     #define MT_ISTMSCP      0x08            /* DEC TMSCP protocol (TU81, TK50) */
     #define MT_ISCY         0x09            /* CCI Cipher */
     #define MT_ISCT         0x0a            /* HP 1/4 tape */
     #define MT_ISFHP        0x0b            /* HP 7980 1/2 tape */
     #define MT_ISEXABYTE    0x0c            /* Exabyte */
     #define MT_ISEXA8200    0x0c            /* Exabyte EXB-8200 */
     #define MT_ISEXA8500    0x0d            /* Exabyte EXB-8500 */
     #define MT_ISVIPER1     0x0e            /* Archive Viper-150 */
     #define MT_ISPYTHON     0x0f            /* Archive Python (DAT) */
     #define MT_ISHPDAT      0x10            /* HP 35450A DAT drive */
     #define MT_ISMFOUR      0x11            /* M4 Data 1/2 9track drive */
     #define MT_ISTK50       0x12            /* DEC SCSI TK50 */
     #define MT_ISMT02       0x13            /* Emulex MT02 SCSI tape controller */

     /* mag tape io control commands */
     #define MTIOCTOP        _IOW(’m’, 1, struct mtop)       /* do a mag tape op */
     #define MTIOCGET        _IOR(’m’, 2, struct mtget)      /* get tape status */
     /* these two do not appear to be used anywhere */
     #define MTIOCIEOT       _IO(’m’, 3)                     /* ignore EOT error */
     #define MTIOCEEOT       _IO(’m’, 4)                     /* enable EOT error */
     /*
      * When more SCSI-3 SSC (streaming device) devices are out there
      * that support the full 32 byte type 2 structure, we’ll have to
      * rethink these ioctls to support all the entities they haul into
      * the picture (64 bit blocks, logical file record numbers, etc..).
      */
     #define MTIOCRDSPOS     _IOR(’m’, 5, u_int32_t) /* get logical blk addr */
     #define MTIOCRDHPOS     _IOR(’m’, 6, u_int32_t) /* get hardware blk addr */
     #define MTIOCSLOCATE    _IOW(’m’, 5, u_int32_t) /* seek to logical blk addr */
     #define MTIOCHLOCATE    _IOW(’m’, 6, u_int32_t) /* seek to hardware blk addr */
     #define MTIOCERRSTAT    _IOR(’m’, 7, union mterrstat)   /* get tape errors */
     /*
      * Set EOT model- argument is number of filemarks to end a tape with.
      * Note that not all possible values will be accepted.
      */
     #define MTIOCSETEOTMODEL        _IOW(’m’, 8, u_int32_t)
     /* Get current EOT model */
     #define MTIOCGETEOTMODEL        _IOR(’m’, 8, u_int32_t)

     #ifndef _KERNEL
     #define DEFTAPE "/dev/nsa0"
     #endif

     #ifdef  _KERNEL
     /*
      * minor device number
      */

     #define T_UNIT          003             /* unit selection */
     #define T_NOREWIND      004             /* no rewind on close */
     #define T_DENSEL        030             /* density select */
     #define T_800BPI        000             /* select  800 bpi */
     #define T_1600BPI       010             /* select 1600 bpi */
     #define T_6250BPI       020             /* select 6250 bpi */
     #define T_BADBPI        030             /* undefined selection */
     #endif

     #endif /* !_SYS_MTIO_H_ */

FILES

     /dev/[n]sa*

SEE ALSO

     mt(1), tar(1), ast(4), sa(4)

HISTORY

     The mtio manual appeared in 4.2BSD.  An i386 version first appeared in
     FreeBSD 2.2.

BUGS

     The status should be returned in a device independent format.

     The special file naming should be redone in a more consistent and
     understandable manner.