.\" Copyright (c) 1996
.\"	Mike Pritchard <mpp@FreeBSD.org>.  All rights reserved.
.\"
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.\"	The Regents of the University of California.  All rights reserved.
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.\"     @(#)mtio.4	8.1 (Berkeley) 6/5/93
.\" $FreeBSD$
.\"
.Dd November 11, 2011
.Dt MTIO 4
.Os
.Sh NAME
.Nm mtio
.Nd FreeBSD magtape interface
.Sh DESCRIPTION
The special files
named
.Pa /dev/[n]sa*
refer to SCSI tape drives,
which may be attached to the system.
.Pa /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.
.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
Tapes can be written with either fixed length records or variable length
records.
See
.Xr 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.
.Pp
All of the magtape devices may be manipulated with the
.Xr mt 1
command.
.Pp
A number of
.Xr ioctl 2
operations are available
on raw magnetic tape.
The following definitions are from
.In sys/mtio.h :
.Bd  -literal
#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 */
	int32_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 */
	/*
	 * Note that the residual count, while maintained, may be
	 * be nonsense because the size of the residual may (greatly)
	 * exceed 32 K-bytes. Use the MTIOCERRSTAT ioctl to get a
	 * more accurate count.
	 */
	short	mt_resid;	/* residual count */
#if defined (__FreeBSD__)
	int32_t mt_blksiz;	/* presently operating blocksize */
	int32_t mt_density;	/* presently operating density */
	uint32_t mt_comp;	/* presently operating compression */
	int32_t mt_blksiz0;	/* blocksize for mode 0 */
	int32_t mt_blksiz1;	/* blocksize for mode 1 */
	int32_t mt_blksiz2;	/* blocksize for mode 2 */
	int32_t mt_blksiz3;	/* blocksize for mode 3 */
	int32_t mt_density0;	/* density for mode 0 */
	int32_t mt_density1;	/* density for mode 1 */
	int32_t mt_density2;	/* density for mode 2 */
	int32_t mt_density3;	/* density for mode 3 */
/* the following are not yet implemented */
	uint32_t mt_comp0;	/* compression type for mode 0 */
	uint32_t mt_comp1;	/* compression type for mode 1 */
	uint32_t mt_comp2;	/* compression type for mode 2 */
	uint32_t mt_comp3;	/* compression type for mode 3 */
/* end not yet implemented */
#endif
	int32_t	mt_fileno;	/* relative file number of current position */
	int32_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.
	 */
	uint8_t io_sense[32];	/* Last Sense Data For Data I/O */
	int32_t io_resid;	/* residual count from last Data I/O */
	uint8_t io_cdb[16];	/* Command that Caused the Last Data Sense */
	uint8_t ctl_sense[32];	/* Last Sense Data For Control I/O */
	int32_t ctl_resid;	/* residual count from last Control I/O */
	uint8_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 {
		uint32_t retries;	/* total # retries performed */
		uint32_t corrected;	/* total # corrections performed */
		uint32_t processed;	/* total # corrections successful */
		uint32_t failures;	/* total # corrections/retries failed */
		uint64_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, uint32_t)	/* get logical blk addr */
#define	MTIOCRDHPOS	_IOR('m', 6, uint32_t)	/* get hardware blk addr */
#define	MTIOCSLOCATE	_IOW('m', 5, uint32_t)	/* seek to logical blk addr */
#define	MTIOCHLOCATE	_IOW('m', 6, uint32_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, uint32_t)
/* Get current EOT model */
#define	MTIOCGETEOTMODEL	_IOR('m', 8, uint32_t)

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

#endif /* !_SYS_MTIO_H_ */
.Ed
.Sh FILES
.Bl -tag -width /dev/[n]sa* -compact
.It Pa /dev/[n]sa*
.El
.Sh SEE ALSO
.Xr mt 1 ,
.Xr tar 1 ,
.Xr ast 4 ,
.Xr sa 4
.Sh HISTORY
The
.Nm
manual appeared in
.Bx 4.2 .
An i386 version first appeared in
.Fx 2.2 .
.Sh BUGS
The status should be returned in a device independent format.
.Pp
The special file naming should be redone in a more consistent and
understandable manner.