Merging upstream version 6.8.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 0 insertions, 950 deletions

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-.\" Copyright 1995 Robert K. Nichols (Robert.K.Nichols@att.com)
-.\" Copyright 1999-2005 Kai Mäkisara (Kai.Makisara@kolumbus.fi)
-.\"
-.\" SPDX-License-Identifier: Linux-man-pages-copyleft
-.TH st 4 2023-10-31 "Linux man-pages 6.7"
-.SH NAME
-st \- SCSI tape device
-.SH SYNOPSIS
-.nf
-.B #include <sys/mtio.h>
-.P
-.BI "int ioctl(int " fd ", int " request " [, (void *)" arg3 "]);"
-.BI "int ioctl(int " fd ", MTIOCTOP, (struct mtop *)" mt_cmd );
-.BI "int ioctl(int " fd ", MTIOCGET, (struct mtget *)" mt_status );
-.BI "int ioctl(int " fd ", MTIOCPOS, (struct mtpos *)" mt_pos );
-.fi
-.SH DESCRIPTION
-The
-.B st
-driver provides the interface to a variety of SCSI tape devices.
-Currently, the driver takes control of all detected devices of type
-\[lq]sequential-access\[rq].
-The
-.B st
-driver uses major device number 9.
-.P
-Each device uses eight minor device numbers.
-The lowermost five bits
-in the minor numbers are assigned sequentially in the order of
-detection.
-In the 2.6 kernel, the bits above the eight lowermost bits are
-concatenated to the five lowermost bits to form the tape number.
-The minor numbers can be grouped into
-two sets of four numbers: the principal (auto-rewind) minor device numbers,
-.IR n ,
-and the \[lq]no-rewind\[rq] device numbers,
-.RI ( n " + 128)."
-Devices opened using the principal device number will be sent a
-.B REWIND
-command when they are closed.
-Devices opened using the \[lq]no-rewind\[rq] device number will not.
-(Note that using an auto-rewind device for positioning the tape with,
-for instance, mt does not lead to the desired result: the tape is
-rewound after the mt command and the next command starts from the
-beginning of the tape).
-.P
-Within each group, four minor numbers are available to define
-devices with different characteristics (block size, compression,
-density, etc.)
-When the system starts up, only the first device is available.
-The other three are activated when the default
-characteristics are defined (see below).
-(By changing compile-time
-constants, it is possible to change the balance between the maximum
-number of tape drives and the number of minor numbers for each
-drive.
-The default allocation allows control of 32 tape drives.
-For instance, it is possible to control up to 64 tape drives
-with two minor numbers for different options.)
-.P
-Devices are typically created by:
-.P
-.in +4n
-.EX
-mknod \-m 666 /dev/st0 c 9 0
-mknod \-m 666 /dev/st0l c 9 32
-mknod \-m 666 /dev/st0m c 9 64
-mknod \-m 666 /dev/st0a c 9 96
-mknod \-m 666 /dev/nst0 c 9 128
-mknod \-m 666 /dev/nst0l c 9 160
-mknod \-m 666 /dev/nst0m c 9 192
-mknod \-m 666 /dev/nst0a c 9 224
-.EE
-.in
-.P
-There is no corresponding block device.
-.P
-The driver uses an internal buffer that has to be large enough to hold
-at least one tape block.
-Before Linux 2.1.121, the buffer is
-allocated as one contiguous block.
-This limits the block size to the
-largest contiguous block of memory the kernel allocator can provide.
-The limit is currently 128\ kB for 32-bit architectures and
-256\ kB for 64-bit architectures.
-In newer kernels the driver
-allocates the buffer in several parts if necessary.
-By default, the
-maximum number of parts is 16.
-This means that the maximum block size
-is very large (2\ MB if allocation of 16 blocks of 128\ kB succeeds).
-.P
-The driver's internal buffer size is determined by a compile-time
-constant which can be overridden with a kernel startup option.
-In addition to this, the driver tries to allocate a larger temporary
-buffer at run time if necessary.
-However, run-time allocation of large
-contiguous blocks of memory may fail and it is advisable not to rely
-too much on dynamic buffer allocation before Linux 2.1.121
-(this applies also to demand-loading the driver with kerneld or kmod).
-.P
-The driver does not specifically support any tape drive brand or
-model.
-After system start-up the tape device options are defined by
-the drive firmware.
-For example, if the drive firmware selects fixed-block mode,
-the tape device uses fixed-block mode.
-The options can
-be changed with explicit
-.BR ioctl (2)
-calls and remain in effect when the device is closed and reopened.
-Setting the options affects both the auto-rewind and the nonrewind
-device.
-.P
-Different options can be specified for the different devices within
-the subgroup of four.
-The options take effect when the device is
-opened.
-For example, the system administrator can define
-one device that writes in fixed-block mode with a certain block size,
-and one which writes in variable-block mode (if the drive supports
-both modes).
-.P
-The driver supports
-.B tape partitions
-if they are supported by the drive.
-(Note that the tape partitions
-have nothing to do with disk partitions.
-A partitioned tape can be
-seen as several logical tapes within one medium.)
-Partition support has to be enabled with an
-.BR ioctl (2).
-The tape
-location is preserved within each partition across partition changes.
-The partition used for subsequent tape operations is
-selected with an
-.BR ioctl (2).
-The partition switch is executed together with
-the next tape operation in order to avoid unnecessary tape
-movement.
-The maximum number of partitions on a tape is defined by a
-compile-time constant (originally four).
-The driver contains an
-.BR ioctl (2)
-that can format a tape with either one or two partitions.
-.P
-Device
-.I /dev/tape
-is usually created as a hard or soft link to the default tape device
-on the system.
-.P
-Starting from Linux 2.6.2, the driver exports in the sysfs directory
-.I /sys/class/scsi_tape
-the attached devices and some parameters assigned to the devices.
-.SS Data transfer
-The driver supports operation in both fixed-block mode and
-variable-block mode (if supported by the drive).
-In fixed-block mode the drive
-writes blocks of the specified size and the block size is not
-dependent on the byte counts of the write system calls.
-In variable-block mode one tape block is written for each write call
-and the byte
-count determines the size of the corresponding tape block.
-Note that
-the blocks on the tape don't contain any information about the
-writing mode: when reading, the only important thing is to use
-commands that accept the block sizes on the tape.
-.P
-In variable-block mode the read byte count does not have to match
-the tape block size exactly.
-If the byte count is larger than the
-next block on tape, the driver returns the data and the function
-returns the actual block size.
-If the block size is larger than the
-byte count, an error is returned.
-.P
-In fixed-block mode the read byte counts can be arbitrary if
-buffering is enabled, or a multiple of the tape block size if
-buffering is disabled.
-Before Linux 2.1.121 allow writes with
-arbitrary byte count if buffering is enabled.
-In all other cases
-(before Linux 2.1.121 with buffering disabled or newer kernel) the
-write byte count must be a multiple of the tape block size.
-.P
-In Linux 2.6, the driver tries to use direct transfers between the user
-buffer and the device.
-If this is not possible, the driver's internal buffer
-is used.
-The reasons for not using direct transfers include improper alignment
-of the user buffer (default is 512 bytes but this can be changed by the HBA
-driver), one or more pages of the user buffer not reachable by the
-SCSI adapter, and so on.
-.P
-A filemark is automatically written to tape if the last tape operation
-before close was a write.
-.P
-When a filemark is encountered while reading, the following
-happens.
-If there are data remaining in the buffer when the filemark
-is found, the buffered data is returned.
-The next read returns zero
-bytes.
-The following read returns data from the next file.
-The end of
-recorded data is signaled by returning zero bytes for two consecutive
-read calls.
-The third read returns an error.
-.SS Ioctls
-The driver supports three
-.BR ioctl (2)
-requests.
-Requests not recognized by the
-.B st
-driver are passed to the
-.B SCSI
-driver.
-The definitions below are from
-.IR /usr/include/linux/mtio.h :
-.SS MTIOCTOP \[em] perform a tape operation
-This request takes an argument of type
-.IR "(struct mtop\ *)" .
-Not all drives support all operations.
-The driver returns an
-.B EIO
-error if the drive rejects an operation.
-.P
-.in +4n
-.EX
-/* Structure for MTIOCTOP \- mag tape op command: */
-struct mtop {
-    short   mt_op;       /* operations defined below */
-    int     mt_count;    /* how many of them */
-};
-.EE
-.in
-.P
-Magnetic tape operations for normal tape use:
-.TP
-.B MTBSF
-Backward space over
-.I mt_count
-filemarks.
-.TP
-.B MTBSFM
-Backward space over
-.I mt_count
-filemarks.
-Reposition the tape to the EOT side of the last filemark.
-.TP
-.B MTBSR
-Backward space over
-.I mt_count
-records (tape blocks).
-.TP
-.B MTBSS
-Backward space over
-.I mt_count
-setmarks.
-.TP
-.B MTCOMPRESSION
-Enable compression of tape data within the drive if
-.I mt_count
-is nonzero and disable compression if
-.I mt_count
-is zero.
-This command uses the MODE page 15 supported by most DATs.
-.TP
-.B MTEOM
-Go to the end of the recorded media (for appending files).
-.TP
-.B MTERASE
-Erase tape.
-With Linux 2.6, short erase (mark tape empty) is performed if the
-argument is zero.
-Otherwise, long erase (erase all) is done.
-.TP
-.B MTFSF
-Forward space over
-.I mt_count
-filemarks.
-.TP
-.B MTFSFM
-Forward space over
-.I mt_count
-filemarks.
-Reposition the tape to the BOT side of the last filemark.
-.TP
-.B MTFSR
-Forward space over
-.I mt_count
-records (tape blocks).
-.TP
-.B MTFSS
-Forward space over
-.I mt_count
-setmarks.
-.TP
-.B MTLOAD
-Execute the SCSI load command.
-A special case is available for some HP
-autoloaders.
-If
-.I mt_count
-is the constant
-.B MT_ST_HPLOADER_OFFSET
-plus a number, the number is
-sent to the drive to control the autoloader.
-.TP
-.B MTLOCK
-Lock the tape drive door.
-.TP
-.B MTMKPART
-Format the tape into one or two partitions.
-If
-.I mt_count
-is positive, it gives the size of partition 1 and partition
-0 contains the rest of the tape.
-If
-.I mt_count
-is zero, the tape is formatted into one partition.
-From Linux 4.6,
-.\" commit 8038e6456a3e6f5c4759e0d73c4f9165b90c93e7
-a negative
-.I mt_count
-specifies the size of partition 0 and
-the rest of the tape contains partition 1.
-The physical ordering of partitions depends on the drive.
-This command is not allowed for a drive unless the partition support
-is enabled for the drive (see
-.B MT_ST_CAN_PARTITIONS
-below).
-.TP
-.B MTNOP
-No op\[em]flushes the driver's buffer as a side effect.
-Should be used before reading status with
-.BR MTIOCGET .
-.TP
-.B MTOFFL
-Rewind and put the drive off line.
-.TP
-.B MTRESET
-Reset drive.
-.TP
-.B MTRETEN
-Re-tension tape.
-.TP
-.B MTREW
-Rewind.
-.TP
-.B MTSEEK
-Seek to the tape block number specified in
-.IR mt_count .
-This operation requires either a SCSI-2 drive that supports the
-.B LOCATE
-command (device-specific address)
-or a Tandberg-compatible SCSI-1 drive (Tandberg, Archive
-Viper, Wangtek, ...).
-The block number should be one that was previously returned by
-.B MTIOCPOS
-if device-specific addresses are used.
-.TP
-.B MTSETBLK
-Set the drive's block length to the value specified in
-.IR mt_count .
-A block length of zero sets the drive to variable block size mode.
-.TP
-.B MTSETDENSITY
-Set the tape density to the code in
-.IR mt_count .
-The density codes supported by a drive can be found from the drive
-documentation.
-.TP
-.B MTSETPART
-The active partition is switched to
-.IR mt_count .
-The partitions are numbered from zero.
-This command is not allowed for
-a drive unless the partition support is enabled for the drive (see
-.B MT_ST_CAN_PARTITIONS
-below).
-.TP
-.B MTUNLOAD
-Execute the SCSI unload command (does not eject the tape).
-.TP
-.B MTUNLOCK
-Unlock the tape drive door.
-.TP
-.B MTWEOF
-Write
-.I mt_count
-filemarks.
-.TP
-.B MTWSM
-Write
-.I mt_count
-setmarks.
-.P
-Magnetic tape operations for setting of device options (by the superuser):
-.TP
-.B MTSETDRVBUFFER
-Set various drive and driver options according to bits encoded in
-.IR mt_count .
-These consist of the drive's buffering mode, a set of Boolean driver
-options, the buffer write threshold, defaults for the block size and
-density, and timeouts (only since Linux 2.1).
-A single operation can affect only one item in the list below (the
-Booleans counted as one item.)
-.IP
-A value having zeros in the high-order 4 bits will be used to set the
-drive's buffering mode.
-The buffering modes are:
-.RS
-.TP
-.B 0
-The drive will not report
-.B GOOD
-status on write commands until the data
-blocks are actually written to the medium.
-.TP
-.B 1
-The drive may report
-.B GOOD
-status on write commands as soon as all the
-data has been transferred to the drive's internal buffer.
-.TP
-.B 2
-The drive may report
-.B GOOD
-status on write commands as soon as (a) all
-the data has been transferred to the drive's internal buffer, and
-(b) all buffered data from different initiators has been successfully
-written to the medium.
-.RE
-.IP
-To control the write threshold the value in
-.I mt_count
-must include the constant
-.B MT_ST_WRITE_THRESHOLD
-bitwise ORed with a block count in the low 28 bits.
-The block count refers to 1024-byte blocks, not the physical block
-size on the tape.
-The threshold cannot exceed the driver's internal buffer size (see
-DESCRIPTION, above).
-.IP
-To set and clear the Boolean options
-the value in
-.I mt_count
-must include one of the constants
-.BR MT_ST_BOOLEANS ,
-.BR MT_ST_SETBOOLEANS ,
-.BR MT_ST_CLEARBOOLEANS ,
-or
-.B MT_ST_DEFBOOLEANS
-bitwise ORed with
-whatever combination of the following options is desired.
-Using
-.B MT_ST_BOOLEANS
-the options can be set to the values
-defined in the corresponding bits.
-With
-.B MT_ST_SETBOOLEANS
-the options can be selectively set and with
-.B MT_ST_DEFBOOLEANS
-selectively cleared.
-.IP
-The default options for a tape device are set with
-.BR MT_ST_DEFBOOLEANS .
-A nonactive tape device (e.g., device with
-minor 32 or 160) is activated when the default options for it are
-defined the first time.
-An activated device inherits from the device
-activated at start-up the options not set explicitly.
-.IP
-The Boolean options are:
-.RS
-.TP
-.BR MT_ST_BUFFER_WRITES " (Default: true)"
-Buffer all write operations in fixed-block mode.
-If this option is false and the drive uses a fixed block size, then
-all write operations must be for a multiple of the block size.
-This option must be set false to write reliable multivolume archives.
-.TP
-.BR MT_ST_ASYNC_WRITES " (Default: true)"
-When this option is true, write operations return immediately without
-waiting for the data to be transferred to the drive if the data fits
-into the driver's buffer.
-The write threshold determines how full the buffer must be before a
-new SCSI write command is issued.
-Any errors reported by the drive will be held until the next
-operation.
-This option must be set false to write reliable multivolume archives.
-.TP
-.BR MT_ST_READ_AHEAD " (Default: true)"
-This option causes the driver to provide read buffering and
-read-ahead in fixed-block mode.
-If this option is false and the drive uses a fixed block size, then
-all read operations must be for a multiple of the block size.
-.TP
-.BR MT_ST_TWO_FM " (Default: false)"
-This option modifies the driver behavior when a file is closed.
-The normal action is to write a single filemark.
-If the option is true, the driver will write two filemarks and
-backspace over the second one.
-.IP
-Note:
-This option should not be set true for QIC tape drives since they are
-unable to overwrite a filemark.
-These drives detect the end of recorded data by testing for blank tape
-rather than two consecutive filemarks.
-Most other current drives also
-detect the end of recorded data and using two filemarks is usually
-necessary only when interchanging tapes with some other systems.
-.TP
-.BR MT_ST_DEBUGGING " (Default: false)"
-This option turns on various debugging messages from the driver
-(effective only if the driver was compiled with
-.B DEBUG
-defined nonzero).
-.TP
-.BR MT_ST_FAST_EOM " (Default: false)"
-This option causes the
-.B MTEOM
-operation to be sent directly to the
-drive, potentially speeding up the operation but causing the driver to
-lose track of the current file number normally returned by the
-.B MTIOCGET
-request.
-If
-.B MT_ST_FAST_EOM
-is false, the driver will respond to an
-.B MTEOM
-request by forward spacing over files.
-.TP
-.BR MT_ST_AUTO_LOCK " (Default: false)"
-When this option is true, the drive door is locked when the device file is
-opened and unlocked when it is closed.
-.TP
-.BR MT_ST_DEF_WRITES " (Default: false)"
-The tape options (block size, mode, compression, etc.) may change
-when changing from one device linked to a drive to another device
-linked to the same drive depending on how the devices are
-defined.
-This option defines when the changes are enforced by the
-driver using SCSI-commands and when the drives auto-detection
-capabilities are relied upon.
-If this option is false, the driver
-sends the SCSI-commands immediately when the device is changed.
-If the
-option is true, the SCSI-commands are not sent until a write is
-requested.
-In this case, the drive firmware is allowed to detect the
-tape structure when reading and the SCSI-commands are used only to
-make sure that a tape is written according to the correct specification.
-.TP
-.BR MT_ST_CAN_BSR " (Default: false)"
-When read-ahead is used, the tape must sometimes be spaced backward to the
-correct position when the device is closed and the SCSI command to
-space backward over records is used for this purpose.
-Some older
-drives can't process this command reliably and this option can be used
-to instruct the driver not to use the command.
-The end result is that,
-with read-ahead and fixed-block mode, the tape may not be correctly
-positioned within a file when the device is closed.
-With Linux 2.6, the
-default is true for drives supporting SCSI-3.
-.TP
-.BR MT_ST_NO_BLKLIMS " (Default: false)"
-Some drives don't accept the
-.B "READ BLOCK LIMITS"
-SCSI command.
-If this is used, the driver does not use the command.
-The drawback is
-that the driver can't check before sending commands if the selected
-block size is acceptable to the drive.
-.TP
-.BR MT_ST_CAN_PARTITIONS " (Default: false)"
-This option enables support for several partitions within a
-tape.
-The option applies to all devices linked to a drive.
-.TP
-.BR MT_ST_SCSI2LOGICAL " (Default: false)"
-This option instructs the driver to use the logical block addresses
-defined in the SCSI-2 standard when performing the seek and tell
-operations (both with
-.B MTSEEK
-and
-.B MTIOCPOS
-commands and when changing tape
-partition).
-Otherwise, the device-specific addresses are used.
-It is highly advisable to set this option if the drive supports the
-logical addresses because they count also filemarks.
-There are some
-drives that support only the logical block addresses.
-.TP
-.BR MT_ST_SYSV " (Default: false)"
-When this option is enabled, the tape devices use the System V
-semantics.
-Otherwise, the BSD semantics are used.
-The most important
-difference between the semantics is what happens when a device used
-for reading is closed: in System V semantics the tape is spaced forward
-past the next filemark if this has not happened while using the
-device.
-In BSD semantics the tape position is not changed.
-.TP
-.BR MT_NO_WAIT " (Default: false)"
-Enables immediate mode (i.e., don't wait for the command to finish) for some
-commands (e.g., rewind).
-.P
-An example:
-.P
-.in +4n
-.EX
-struct mtop mt_cmd;
-mt_cmd.mt_op = MTSETDRVBUFFER;
-mt_cmd.mt_count = MT_ST_BOOLEANS |
-        MT_ST_BUFFER_WRITES | MT_ST_ASYNC_WRITES;
-ioctl(fd, MTIOCTOP, mt_cmd);
-.EE
-.in
-.P
-The default block size for a device can be set with
-.B MT_ST_DEF_BLKSIZE
-and the default density code can be set with
-.BR MT_ST_DEFDENSITY .
-The values for the parameters are or'ed
-with the operation code.
-.P
-With Linux 2.1.x and later, the timeout values can be set with the
-subcommand
-.B MT_ST_SET_TIMEOUT
-ORed with the timeout in seconds.
-The long timeout (used for rewinds and other commands
-that may take a long time) can be set with
-.BR MT_ST_SET_LONG_TIMEOUT .
-The kernel defaults are very long to
-make sure that a successful command is not timed out with any
-drive.
-Because of this, the driver may seem stuck even if it is only
-waiting for the timeout.
-These commands can be used to set more
-practical values for a specific drive.
-The timeouts set for one device
-apply for all devices linked to the same drive.
-.P
-Starting from Linux 2.4.19 and Linux 2.5.43, the driver supports a status
-bit which indicates whether the drive requests cleaning.
-The method used by the
-drive to return cleaning information is set using the
-.B MT_ST_SEL_CLN
-subcommand.
-If the value is zero, the cleaning
-bit is always zero.
-If the value is one, the TapeAlert data defined
-in the SCSI-3 standard is used (not yet implemented).
-Values 2\[en]17 are
-reserved.
-If the lowest eight bits are >= 18, bits from the extended
-sense data are used.
-The bits 9\[en]16 specify a mask to select the bits
-to look at and the bits 17\[en]23 specify the bit pattern to look for.
-If the bit pattern is zero, one or more bits under the mask indicate
-the cleaning request.
-If the pattern is nonzero, the pattern must match
-the masked sense data byte.
-.RE
-.SS MTIOCGET \[em] get status
-This request takes an argument of type
-.IR "(struct mtget\ *)" .
-.P
-.in +4n
-.EX
-/* structure for MTIOCGET \- mag tape get status command */
-struct mtget {
-    long     mt_type;
-    long     mt_resid;
-    /* the following registers are device dependent */
-    long     mt_dsreg;
-    long     mt_gstat;
-    long     mt_erreg;
-    /* The next two fields are not always used */
-    daddr_t  mt_fileno;
-    daddr_t  mt_blkno;
-};
-.EE
-.in
-.TP
-\fImt_type\fP
-The header file defines many values for
-.IR mt_type ,
-but the current driver reports only the generic types
-.B MT_ISSCSI1
-(Generic SCSI-1 tape)
-and
-.B MT_ISSCSI2
-(Generic SCSI-2 tape).
-.TP
-\fImt_resid\fP
-contains the current tape partition number.
-.TP
-\fImt_dsreg\fP
-reports the drive's current settings for block size (in the low 24
-bits) and density (in the high 8 bits).
-These fields are defined by
-.BR MT_ST_BLKSIZE_SHIFT ,
-.BR MT_ST_BLKSIZE_MASK ,
-.BR MT_ST_DENSITY_SHIFT ,
-and
-.BR MT_ST_DENSITY_MASK .
-.TP
-\fImt_gstat\fP
-reports generic (device independent) status information.
-The header file defines macros for testing these status bits:
-.RS
-.TP
-\fBGMT_EOF\fP(\fIx\fP)
-The tape is positioned just after a filemark
-(always false after an
-.B MTSEEK
-operation).
-.TP
-\fBGMT_BOT\fP(\fIx\fP)
-The tape is positioned at the beginning of the first file (always false
-after an
-.B MTSEEK
-operation).
-.TP
-\fBGMT_EOT\fP(\fIx\fP)
-A tape operation has reached the physical End Of Tape.
-.TP
-\fBGMT_SM\fP(\fIx\fP)
-The tape is currently positioned at a setmark
-(always false after an
-.B MTSEEK
-operation).
-.TP
-\fBGMT_EOD\fP(\fIx\fP)
-The tape is positioned at the end of recorded data.
-.TP
-\fBGMT_WR_PROT\fP(\fIx\fP)
-The drive is write-protected.
-For some drives this can also mean that the drive does not support
-writing on the current medium type.
-.TP
-\fBGMT_ONLINE\fP(\fIx\fP)
-The last
-.BR open (2)
-found the drive with a tape in place and ready for operation.
-.TP
-\fBGMT_D_6250\fP(\fIx\fP)
-.TQ
-\fBGMT_D_1600\fP(\fIx\fP)
-.TQ
-\fBGMT_D_800\fP(\fIx\fP)
-This \[lq]generic\[rq] status information reports the current
-density setting for 9-track \(12" tape drives only.
-.TP
-\fBGMT_DR_OPEN\fP(\fIx\fP)
-The drive does not have a tape in place.
-.TP
-\fBGMT_IM_REP_EN\fP(\fIx\fP)
-Immediate report mode.
-This bit is set if there are no guarantees that
-the data has been physically written to the tape when the write call
-returns.
-It is set zero only when the driver does not buffer data and
-the drive is set not to buffer data.
-.TP
-\fBGMT_CLN\fP(\fIx\fP)
-The drive has requested cleaning.
-Implemented since Linux 2.4.19 and Linux 2.5.43.
-.RE
-.TP
-\fImt_erreg\fP
-The only field defined in
-.I mt_erreg
-is the recovered error count in the low 16 bits (as defined by
-.B MT_ST_SOFTERR_SHIFT
-and
-.BR MT_ST_SOFTERR_MASK ).
-Due to inconsistencies in the way drives report recovered errors, this
-count is often not maintained (most drives do not by default report
-soft errors but this can be changed with a SCSI MODE SELECT command).
-.TP
-\fImt_fileno\fP
-reports the current file number (zero-based).
-This value is set to \-1 when the file number is unknown (e.g., after
-.B MTBSS
-or
-.BR MTSEEK ).
-.TP
-\fImt_blkno\fP
-reports the block number (zero-based) within the current file.
-This value is set to \-1 when the block number is unknown (e.g., after
-.BR MTBSF ,
-.BR MTBSS ,
-or
-.BR MTSEEK ).
-.SS MTIOCPOS \[em] get tape position
-This request takes an argument of type
-.I "(struct mtpos\ *)"
-and reports the drive's notion of the current tape block number,
-which is not the same as
-.I mt_blkno
-returned by
-.BR MTIOCGET .
-This drive must be a SCSI-2 drive that supports the
-.B "READ POSITION"
-command (device-specific address)
-or a Tandberg-compatible SCSI-1 drive (Tandberg, Archive
-Viper, Wangtek, ... ).
-.P
-.in +4n
-.EX
-/* structure for MTIOCPOS \- mag tape get position command */
-struct mtpos {
-    long mt_blkno;    /* current block number */
-};
-.EE
-.in
-.SH RETURN VALUE
-.TP
-.B EACCES
-An attempt was made to write or erase a write-protected tape.
-(This error is not detected during
-.BR open (2).)
-.TP
-.B EBUSY
-The device is already in use or the driver was unable to allocate a
-buffer.
-.TP
-.B EFAULT
-The command parameters point to memory not belonging to the calling
-process.
-.TP
-.B EINVAL
-An
-.BR ioctl (2)
-had an invalid argument, or a requested block size was invalid.
-.TP
-.B EIO
-The requested operation could not be completed.
-.TP
-.B ENOMEM
-The byte count in
-.BR read (2)
-is smaller than the next physical block on the tape.
-(Before Linux 2.2.18 and Linux 2.4.0 the extra bytes have been
-.\" Precisely: Linux 2.6.0-test6
-silently ignored.)
-.TP
-.B ENOSPC
-A write operation could not be completed because the tape reached
-end-of-medium.
-.TP
-.B ENOSYS
-Unknown
-.BR ioctl (2).
-.TP
-.B ENXIO
-During opening, the tape device does not exist.
-.TP
-.B EOVERFLOW
-An attempt was made to read or write a variable-length block that is
-larger than the driver's internal buffer.
-.TP
-.B EROFS
-Open is attempted with
-.B O_WRONLY
-or
-.B O_RDWR
-when the tape in the drive is write-protected.
-.SH FILES
-.TP
-.I /dev/st*
-the auto-rewind SCSI tape devices
-.TP
-.I /dev/nst*
-the nonrewind SCSI tape devices
-.\" .SH AUTHOR
-.\" The driver has been written by Kai M\(:akisara (Kai.Makisara@metla.fi)
-.\" starting from a driver written by Dwayne Forsyth.
-.\" Several other
-.\" people have also contributed to the driver.
-.SH NOTES
-.IP \[bu] 3
-When exchanging data between systems, both systems have to agree on
-the physical tape block size.
-The parameters of a drive after startup
-are often not the ones most operating systems use with these
-devices.
-Most systems use drives in variable-block mode if the drive
-supports that mode.
-This applies to most modern drives, including
-DATs, 8mm helical scan drives, DLTs, etc.
-It may be advisable to use
-these drives in variable-block mode also in Linux (i.e., use
-.B MTSETBLK
-or
-.B MTSETDEFBLK
-at system startup to set the mode), at least when
-exchanging data with a foreign system.
-The drawback of
-this is that a fairly large tape block size has to be used to get
-acceptable data transfer rates on the SCSI bus.
-.IP \[bu]
-Many programs (e.g.,
-.BR tar (1))
-allow the user to specify the blocking
-factor on the command line.
-Note that this determines the physical block
-size on tape only in variable-block mode.
-.IP \[bu]
-In order to use SCSI tape drives, the basic SCSI driver,
-a SCSI-adapter driver and the SCSI tape driver must be either
-configured into the kernel or loaded as modules.
-If the SCSI-tape
-driver is not present, the drive is recognized but the tape support
-described in this page is not available.
-.IP \[bu]
-The driver writes error messages to the console/log.
-The SENSE
-codes written into some messages are automatically translated to text
-if verbose SCSI messages are enabled in kernel configuration.
-.IP \[bu]
-The driver's internal buffering allows good throughput in fixed-block
-mode also with small
-.BR read (2)
-and
-.BR write (2)
-byte counts.
-With direct transfers
-this is not possible and may cause a surprise when moving to the 2.6
-kernel.
-The solution is to tell the software to use larger transfers (often
-telling it to use larger blocks).
-If this is not possible, direct transfers can be disabled.
-.SH SEE ALSO
-.BR mt (1)
-.P
-The file
-.I drivers/scsi/README.st
-or
-.I Documentation/scsi/st.txt
-(kernel >= 2.6) in the Linux kernel source tree contains
-the most recent information about the driver and its configuration
-possibilities