NAME
mtio —
UNIX magtape interface
DESCRIPTION
The special files named /dev/cy0s, /dev/cy15s are interfaces to the UNIX magtape drivers. For the Tahoe, these interfaces may be on the VERSABUS via a CIPHER tapemaster formatter cy(4). The files cy0s, cy15s are read/written in 25 IPS, The density (1600 BPI or 3200 BPI) is selected by a switch on the drive. The following table of device names applies to any of the transport/controller pairs.| 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 |
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.
For compatibility with customary UNIX tape device names “mt*”, the [n] cy*s files are linked to appropriate [n] mt* files.
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 other 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/cy?,
- /dev/rcy?
- Rewind devices.
- /dev/ncy?,
- /dev/nrcy?
- No-rewind devices.
- /dev/[n]mt?,
- /dev/[n]rmt?
- Linked device names.