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.\"     from: @(#)mtio.4	6.4 (Berkeley) 5/6/91
.\"	$Id: mtio.4,v 1.1 1995/10/18 08:44:33 deraadt Exp $
.\"
.Dd May 6, 1991
.Dt MTIO 4
.Os
.Sh NAME
.Nm mtio
.Nd
.Tn UNIX
magtape interface
.Sh DESCRIPTION
The special files named
.Pa /dev/cy0s ,
...,
.Pa /dev/cy15s
are interfaces to the
.Tn UNIX
magtape drivers.
For the
Tahoe, these interfaces
may be on the
.Tn VERSABUS
via a
.Tn CIPHER
tapemaster formatter
.Xr cy 4 .
The files
.Pa cy0s ,
...,
.Pa cy15s
are read/written in 25
.Tn IPS , 
The density (1600
.Tn BPI
or 3200
.Tn BPI )
is selected by a switch on the drive.
The following table of device names
applies to any of the transport/controller pairs.
.Bl -column "rewindxxx" "No-rewindxxx" "rewindxxxx" "No-rewindxxxx" -offset indent
.Em Rewind	No-rewind	Rewind	No-rewind
cy0s/rcy0s	ncy0s/nrcy0s	cy8s/rcy8s	ncy8s/nrcy8s
cy1s/rcy1s	ncy1s/nrcy1s	cy9s/rcy9s	ncy9s/nrcy9s
cy2s/rcy2s	ncy2s/nrcy2s	cy10s/rcy10s	ncy10s/nrcy10s
cy3s/rcy3s	ncy3s/nrcy3s	cy11s/rcy11s	ncy11s/nrcy11s
cy4s/rcy4s	ncy4s/nrcy4s	cy12s/rcy12s	ncy12s/nrcy12s
cy5s/rcy5s	ncy5s/nrcy5s	cy13s/rcy13s	ncy13s/nrcy13s
cy6s/rcy6s	ncy6s/nrcy6s	cy14s/rcy14s	ncy14s/nrcy14s
cy7s/rcy7s	ncy7s/nrcy7s	cy15s/rcy15s	ncy15s/nrcy15s
.El
.Pp
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
.Ql n
is usually prepended to
the name of the no-rewind devices.
.Pp
For compatibility with customary
.Tn UNIX
tape device
names
.Dq Em mt* ,
the
.Bo Pa n Bc Pa cy*s
files are linked to appropriate
.Bo Pa n Bc Em mt*
files.
.Pp
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.
.Pp
All of the magtape devices may be manipulated with the
.Xr mt 1
command.
.Pp
A number of other
.Xr ioctl 2
operations are available
on raw magnetic tape.
The following definitions are from
.Aq Pa sys/mtio.h :
.Bd  -literal
/*
 * 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
.Ed
.Sh FILES
.Bl -tag -width /dev/nrcy? -compact
.It Pa /dev/cy? ,
.It Pa /dev/rcy?
Rewind devices.
.It Pa /dev/ncy? ,
.It Pa /dev/nrcy?
No-rewind devices.
.It Pa /dev/[n]mt? ,
.It Pa /dev/[n]rmt?
Linked device names.
.El
.Sh SEE ALSO
.Xr mt 1 ,
.Xr tar 1 ,
.Xr cy 4