MTIO(4)                OpenBSD Programmer's Manual (VAX)               MTIO(4)

NAME
     mtio - OpenBSD magtape interface

DESCRIPTION
     Each tape subsystem has a couple of special devices associated with it.
     The magtape devices may be on the MASSBUS using the TM03 formatter,
     ht(4), or TM78 formatter, mt(4), or on the UNIBUS/QBUS using either the
     TM11 or TE10 formatters, tm(4), TU45 compatible formatters, ut(4), or
     TS11/TSV05 tape formatters, ts(4). These devices are typical tape block
     devices, see physio(4).

     The conventional device letters/numbers is applicable to any of the
     transport/controller pairs.  (But note that only 1600 BPI is available
     with the TS11, and that 800 BPI is not applicable to TM78.)

     When the device last number is between 0-7 the device will operate at 800
     BPI (or its lowest density), between 8-15 it will operate at 1600 BPI (or
     its second density), and between 16-23 it will operate at 6250 BPI.

     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.

     Unix tapes are written in multiples of 1024 byte block records. 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 posi-
     tioned 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 <sys/mtio.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 */

     /* 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 */
     /* the following two are not yet implemented */
             daddr_t mt_fileno;      /* file number of current position */
             daddr_t mt_blkno;       /* block number of current position */
     /* end not yet implemented */
     };

     /*
      * 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 */

     /* 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 */
     #define MTIOCIEOT       _IO('m', 3)                     /* ignore EOT error */
     #define MTIOCEEOT       _IO('m', 4)                     /* enable EOT error */

     #ifndef KERNEL
     #define DEFTAPE "/dev/rmt12"
     #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

FILES
     /dev/mt?
     /dev/rmt?

SEE ALSO
     mt(1), tar(1), tp(1), ht(4), mt(4), tm(4), ts(4), ut(4)

HISTORY
     The mtio manual appeared in 4.2BSD.

BUGS
     The status should be returned in a device independent format.

OpenBSD 2.9                     January 7, 1996                              2
