TG(4)

NAME
tg - SCSI 1/2-inch magnetic tape interface

SYNOPSIS
device tg0 at ssm? bin 5 maps 512 target 5 unit 0

DESCRIPTION
This device driver supports SCSI target adapters for 1/2-inch magnetic tape drives. All functionality as described in mtio(4) is supported, except where noted. Up to eight tape drive units spread across the SSM boards in the system are supported. The SCSI interface for the SSM board supports the target adapter on the SSM board plus seven additional target adapters.

The minor device number encodes the density, flags and unit number of the device. The bits in the minor device number are as follows: The low order four bits encode the density, the next four bits are the flags, and the next byte contains the logical unit number.

A density code of zero in the minor number results in the front panel density value being used. A density code of one selects the density 1600 and density code three selects the value 6250 b.p.i.

If a write is performed as the last operation before a tg device is closed, two tapemarks will be written to the tape immediately after the last written data. If the tape drive is not to be rewound after closing, the tape head will be positioned between the tape marks.

The standard device names begin with tg followed by a number representing the tape unit and device type. The corresponding raw devices have names that begin with rtg instead of tg.

The standard rewind-on-close devices are as follows:
tg0 - tg7 | units 0-7, front panel density unchanged.
tg16 - tg23 | units 0-7, density 1600 bpi.
tg32 - tg39 | units 0-7, density 6250 bpi.

The standard no-rewind devices are as follows:
tg8 - tg15 | units 0-7, front panel density unchanged.
tg24 - tg31 | units 0-7, density 1600 bpi.
tg40 - tg47 | units 0-7, density 6250 bpi.

BINARY CONFIGURATION
The tg_bconf array in the device driver binary configuration file (/sys/conf/conf_tg.c) must contain an entry for each drive that may be configured; the entries must be in the same order as the ``device'' entries in the kernel configuration file. As installed, tg_bconf has entries for 7 drives. Unused entries are ignored.

  Tuning Parameters
The following tuning parameters are defined for each drive in the tg_bconf array of the binary configuration file:

(1) The name of the vendor for the drive.

(2) The product i.d of the drive.

(3) This field should be 1 if the target adapter type is embedded.

(4) The buf_size field is the size of the address space reserved for DMA transfers.

(5) Flags for configurable features. The flags available are:

    TGC_PRSENSE
        When this flag is set, all SCSI request sense buffers will be printed out, along with the command that caused the sense condition. Otherwise, only sense buffers that are in some way unusual will be printed out, such as media and hardware errors.

    TGC_RSENSE
        When this flag is set, all SCSI request sense buffers associated with SCSI READ operations that caused a sense condition will be printed out.

    TGC_WSENSE
        When this flag is set all SCSI request sense buffers associated with SCSI write and write filemark operations that caused a sense condition will be printed out.

    TGC_SSENSE
        When this flag is set all SCSI request sense buffers associated with SCSI space operations which caused a sense condition will be printed out.

FILES
/dev/tg* | Block magtape devices
/dev/rtg* | Raw magtape devices
/sys/conf/conf_tg.c | Binary configuration file

SEE ALSO
mt(1), mtio(4)

DIAGNOSTICS
In the descriptions that follow, n is the drive number.

tgn: not enough maps available. The tg driver doesn't have enough DMA maps for this drive. Recheck your system configuration to verify that it has been configured properly.

tgn: no write ring. The requested tape drive is loaded with a tape that has no write ring. Corrective action: Unload the tape and attach a write ring to the reel.

tgn: buffer allocation failed. Memory allocation of the request-sense mode select buffer for this tg driver unit failed. Something else in system initialization is out of control or your system lacks sufficient physical memory.

tgn: Illegal or unsupported density requested. This device was opened with a density-select code that is not supported by this tape drive.

tgn: error writing file mark on close. The tg driver's SCSI write file mark command failed. This probably occurred, along with an error, while the system was attempting to write to the medium. The medium might have been protected against writes or against an attempt to write while not at the beginning of tape or logical end of data.

tgn: error on command command; FILEMARK; EOM; ILI. The tg driver is displaying detailed information pertaining to a problem that occurred when the indicated SCSI command was executed. ``FILEMARK'', ``EOM'', and ``ILI'' are displayed only if the corresponding bits for filemark, end of media, and invalid length indicator are set in the request sense data.