mtio man page on 4.4BSD

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MTIO(4)		       BSD/vax Kernel Interfaces Manual		       MTIO(4)

     mtio — UNIX magtape interface

     The special files named /dev/mt0 and /dev/rmt0 through /dev/mt23 and
     /dev/rmt23 refer to UNIX magtape drives, which may be on the MASSBUS
     using the TM03 formatter ht(4), or TM78 formatter, mt(4), or on the
     UNIBUS using either the TM11 or TS11 formatters tm(4), TU45 compatible
     formatters, ut(4), or ts(4).  These devices are typical tape block
     devices, see physio(4).

     The following table of the converntional device names is applicable to
     any of the transport/controller pairs.  (But note that only 1600 BPI is
     available with the TS11.)

				 800 BPI		1600 BPI	       6500 BPI
	   or lowest density			  or second density	 or third density

	   Rewind		mt0/rmt0		mt8/rmt8		mt16/rmt16
	   Rewind		mt1/rmt1		mt9/rmt9		mt17/rmt17
	   Rewind		mt2/rmt2		mt10/rmt10		mt18/rmt18
	   Rewind		mt3/rmt3		mt11/rmt11		mt19/rmt19
	   No-rewind	       nmt4/nrmt4	      nmt12/nrmt12	     nmt20/nrmt20
	   No-rewind	       nmt5/nrmt5	      nmt13/nrmt13	     nmt21/nrmt21
	   No-rewind	       nmt6/nrmt6	      nmt14/nrmt14	     nmt22/nrmt22
	   No-rewind	       nmt7/nrmt7	      nmt15/nrmt15	     nmt23/nrmt32

     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"

     #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 */


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

     The mtio manual appeared in 4.2BSD.

     The status should be returned in a device independent format.

     The special file naming should be redone in a more consistent and under‐
     standable manner.

4.2 Berkeley Distribution	 June 5, 1993	     4.2 Berkeley Distribution

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