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Diffstat (limited to 'share/man/man4/st.4')
| -rw-r--r-- | share/man/man4/st.4 | 218 |
1 files changed, 141 insertions, 77 deletions
diff --git a/share/man/man4/st.4 b/share/man/man4/st.4 index 5223121880d6..48cd07eec64b 100644 --- a/share/man/man4/st.4 +++ b/share/man/man4/st.4 @@ -14,7 +14,7 @@ driver provides support for a .Em scsi tape. It allows the tape to be run in upto four different modes depending on minor numbers -and supports several different 'close' modes. +and supports several different 'sub modes'. The device can have both a .Em raw interface @@ -52,18 +52,62 @@ and the next, .Em st1 etc. .Pp +.Sh MOUNT SESSIONS The .Nm -driver allows the tape to have four different modes of operation. -They are controlled by bits 2 and 3 of the minor number. In addition, bits -0 and 1 of the minor number are interpretted as being 'close modes'. -The following close modes are supported (1 free, suggestions accepted) +driver is based around the concept of a +.Em Mount Session +, which is defined as the period between the time that a tape is mounted, +and the time when it is unmounted. Any parameters set during a +.Em Mount Session +remain in effect for the remainder of the session or until replaced. The +Tape can be unmounted, bringing the session to a close in several ways. +These include: +.Bl -tag -width ABOUT_THIS_BIG_BUT_REALLY_BIGGER +.It Pa closing an 'unmount device' +This is referred to as sub-mode 00 (see below). An example is /dev/rst0. +.It Pa an MTOFFL ioctl +Reachable throught the 'offline' command of +.Xr st 1 +.It Pa Openning another mode. +Openning a different mode will implicitly unmount the tape, thereby closing +off the mode that was previously mounted. All parameters will be loaded +freshly from the new mode. (see below for more on 'modes'). +.El +.Pp +Parameters that are required to last across the unmounting of a tape, +should be set on the control device. This is submode 3 (see below) and is +reached through a file with a name of the form /dev/st{y}ctl.{x}, where +{y} is the drive number and {x} is the mode number. +.Pp +.Sh MODES AND SUB MODES +There are four Operation modes. These are controlled by bits 2 +and 3 of the minor number and are designed to allow people to easily +read and write different formats of tape on devices that allow +multiple formats. The parameters for each mode can be set individually +by hand with the +.Xr st 1 +variant of the +.Xr mt 1 +command. When a device corresponding to a particular mode is first mounted, +The operating parameters for that +.Em Mount Session +Are copied from that mode. Further changes to the parameters during the +session will change those in effect for the session but not those set +in the Operating Mode. To change the parameters for an Operating Mode, +One must either assign the parameters to the control device, or compile +them into the 'Rogues Gallery' table within the driver. +.Pp +In addition to the four Operation Modes mentionned above, +bits 0 and 1 of the minor number are interpretted as being 'sub-modes'. +The following sub-modes are supported .Bl -tag -width ABOUT_THIS_BIG .It Pa 00 A close will rewind the device. If the tape has been written, then a Filemark will be written before the rewind is requested. +The device is UNMOUNTED. .It Pa 01 -A close will leave the tape loaded. +A close will leave the tape MOUNTED. If the tape was written to a filemark will be written. No other head positioning takes place. Any further reads or writes will occur directly after the @@ -72,76 +116,66 @@ last read, or the written filemark. A close will rewind the device. If the tape has been written, then a Filemark will be written before the rewind is requested. On completion of the rewind an UNLOAD command will be issued. +The device is UNMOUNTED. .It Pa 11 -Not yet defined.. your suggestions welcome? -Possibly like 01 but if the filemark has not already been encountered -on a read, skip forward until it is found. +This is a special mode. +It is known as the +.Em CONTROL DEVICE +for the mode. Parameters set for the mode while in this sub +mode will be remembered from one mount to the next. This allows the +system administrator to set different characteristics (e.g. density, +blocksize, (and eventually compression)) on each mode, and have the +different modes keep those parameters independent of any parameter +changes a user may invoke during a single mount session. At the +completion of the user's mount session, drive parameters will revert +to those set by the administrator. IO operations cannot be performed +on this device/submode. General +.Xr scsi 4 +ioctls +.Em MUST +be performed against the control device. .El - +.Sh BLOCKING MODES Scsi Tapes may run in either 'variable' or 'fixed block' modes. Most QIC type devices run in Fixed block mode, where most 'reel to reel' tapes and many new cartridge formats, allow variable blocksize. The difference between the two is as follows: .Bl -tag -width variable-blocksize .It Pa Variable Blocksize -Each write made to the device results in a single logical record written to -the tape. You can never read or write PART of a record from tape, (though you -may request a larger block and read a smaller record). You cannot read -multiple blocks either. -Data from a single write -is therefore read by a single read. The block size used may be any value -supported by the device, the scsi adapter and the system. -(often variable between 1 byte and 64k (sometimes more)). +Each write made to the device results in a single logical record +written to the tape. You can never read or write PART of a record +from tape, (though you may request a larger block and read a smaller +record). You cannot read multiple blocks either. Data from a single +write is therefore read by a single read. The block size used may +be any value supported by the device, the scsi adapter and the +system. (often variable between 1 byte and 64k (sometimes more)). .Pp -When reading a variable record/block from the tape, -the head is logically considered to be immediatly after the last item read, -and before the next item after that. If the next item is a Filemark, but -you never read it because you have all the data, then the next process to read -will immediatly read the filemark and return EOF. (assuming you were -in non-rewind mode). +When reading a variable record/block from the tape, the head is +logically considered to be immediately after the last item read, +and before the next item after that. If the next item is a Filemark, +but you never read it because you have all the data, then the next +process to read will immediately read the filemark and return EOF. +(assuming you were in non-rewind mode). .It Pa fixed Blocksize -Data written by the user is passed to the tape as a succession of -fixed size blocks. It may be contiguouse in ram and read in a single DMA -pass, however it is considered to be a series of independent blocks. You may -never write an amount of data that is not an exact multiple of the blocksize. -You may read and write the same data as a different set of records, -In other words, blocks that were written together may be read separatly, and -visa versa. +Data written by the user is passed to the tape as a succession of +fixed size blocks. It may be contiguouse in ram and read in a single +DMA pass, however it is considered to be a series of independent +blocks. You may never write an amount of data that is not an exact +multiple of the blocksize. You may read and write the same data +as a different set of records, In other words, blocks that were +written together may be read separatly, and visa versa. .Pp - If you ask for more blocks than there are left in the file, -then the drive will encounter the filemark. Because there is some data to -return to you (unless there were no records before the filemark) the driver -will return the data to you (less than you requested), but hide from -you the discovery of the Filemark. The NEXT read will be returned -immediatly with an EOF. If you never Make the next read, but close the device, -the next process to read -will immediatly read the filemark and return EOF. (assuming you were -in non-rewind mode). +If you ask for more blocks than there are left in the file, then +the drive will encounter the filemark. Because there is some data +to return to you (unless there were no records before the filemark) +the driver will return the data to you (less than you requested), +but hide from you the discovery of the Filemark. The NEXT read +will be returned immediately with an EOF. If you never Make the next +read, but close the device, the next process to read will immediately +read the filemark and return EOF. (assuming you were in non-rewind +mode). .El - -There are four Operation modes. These are controlled by bits 2 and 3 of -the minor number and are designed to allow people to easily read -and write different formats of tape on devices that allow multiple formats. -The formats are: 00-default, 01-high-density, 10-medium-density, and -11-low-density, though the actual densities in high, medium and low -can be set by hand with the -.Xr st 1 -variant of the -.Xr mt 1 -command. -The exact mechanism for setting the densities may change in the future. -.Pp -Because different tape drives behave differently, there is a mechanism -within the source to st, to quickly and conveniently recognise and deal -with brands and models of drive that have special requirements. -.Pp -There is a table (called the rogues gallery) in which the indentification -strings of known errant drives can be stored. Along with each is -a set of flags that allows the setting of densities for each -of the 4 modes, along with a set of 'QUIRK' flags that can be -used to enable or disable sections of code within the driver if a particular -drive is recognised. -.Pp +.Sh FILEMARK HANDLING The handling of filemarks on write is pretty much automatic. If you have written to the tape, and not done a read since, then a filemark will be written to the tape when you close the device. If a rewind is requested @@ -154,9 +188,10 @@ types of tape do not actually write two filemarks to tape, but when read, report a 'phantom' filemark when the last file is read. These devices include the QIC family of devices. It might be that this set of devices is the same set as that of fixed block devices. This has not -been detirmined yet, and they are treated as separate behaviours by the +been detirmined yet, and they are treated as separate behaviors by the driver at this time. .Pp +.SH KERNEL CONFIGURATION In configuring, if an optional .Ar count is given in @@ -164,6 +199,18 @@ the specification, that number of scsi tapes are configured; Most storage for them is allocated only when found so a large number of configured devices is cheap. (once the first has included the driver). .Pp +Because different tape drives behave differently, there is a mechanism +within the source to st, to quickly and conveniently recognise and deal +with brands and models of drive that have special requirements. +.Pp +There is a table (called the rogues gallery) in which the indentification +strings of known errant drives can be stored. Along with each is +a set of flags that allows the setting of densities and blocksizes for each +of the 4 modes, along with a set of 'QUIRK' flags that can be +used to enable or disable sections of code within the driver if a particular +drive is recognised. +.Pp +.Sh IOCTLS The following .Xr ioctl 2 calls apply to scsi tapes. Some also apply to other tapes. They are defined @@ -203,34 +250,51 @@ Enable controller Buffering. .It Pa MTNOCACHE Disable controller Buffering. .It Pa MTSETBSIZ -Set the blocksize to use for the device. If the device is capable of +Set the blocksize to use for the device/mode. If the device is capable of variable blocksize operation, and the blocksize is set to 0, then the drive -will be driven in variable mode. +will be driven in variable mode. This parameter is in effect for the present +mount session only, unless set on the control device. .It Pa MTSETDNSTY Set the Density value (see .Xr st 1 ) to use when running in the mode openned (minor bits 2,3). +This parameter is in effect for the present +mount session only, unless set on the control device. .El .It Pa MTIOCIEOT ?Set END of TAPE processing... not yet supported. .It Pa MTIOCEEOT ?Set END of TAPE processing... not yet supported. .El +.Pp +In addition, The +.Nm +driver will allow the use of any of the general +.Xr scsi 4 +ioctls, as long as the control device is used. .Sh FILES -.Bl -tag -width /dev/[hml][n][e]rst[0-9] -compact -.It Pa /dev/[hml][n][e]rst[0-9] +.Bl -tag -width /dev/[n][e]rst[0-9].[0-3] -compact +.It Pa /dev/[n][e]rst[0-9].[0-3] general form: -.It Pa /dev/hrst0 -High density, rewind on close -.It Pa /dev/mnrst0 -Medium density, No rewind on close -.It Pa /dev/lerst0 -Low density, Eject on close (if capable) +.It Pa /dev/rst0.0 +Mode 0, rewind on close +.It Pa /dev/nrst0.2 +Mode 2, No rewind on close +.It Pa /dev/erst0.3 +Mode 3, Eject on close (if capable) .It Pa /dev/rst0 -default density, rewind on close +Another name for rst0.0 .It Pa /dev/nrst0 -default density, No rewind on close +Another name for nrst0.0 +.It Pa /dev/st0ctl.0 +Parameters set to this device become the default parameters for [en]rst0.0 +.It Pa /dev/st0ctl.1 +Parameters set to this device become the default parameters for [en]rst0.1 +.It Pa /dev/st0ctl.2 +Parameters set to this device become the default parameters for [en]rst0.2 +.It Pa /dev/st0ctl.3 +Parameters set to this device become the default parameters for [en]rst0.3 .El .Sh DIAGNOSTICS None. |