MTIO(4)

NAME
mtio - NetBSD 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 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 <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), tm(4), ts(4), mt(4), ut(4)

HISTORY
The mtio manual appeared in 4.2BSD.

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