160 lines
5.7 KiB
Groff
160 lines
5.7 KiB
Groff
.Dd August 27, 1993
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.Dt SD 4
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.Os FreeBSD
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.Sh NAME
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.Nm scsi
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.Nd scsi system
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.Sh SYNOPSIS
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.Nm controller scbus0
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.Nm controller scbus1 at ahc0
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.Nm controller scbus3 at ahc1 bus 0
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.Nm controller scbus2 at ahc1 bus 1
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.Nm device cd0
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.Nm device ch0
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.Nm disk sd0
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.Nm tape st0
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.Nm device ch1 at scbus0 target 4 unit 0
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.Sh DESCRIPTION
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The
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.Em scsi
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system provides a uniform and modular system for the implementation
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of drivers to control various scsi devices, and to utilize different
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scsi host adapters through host adapter drivers. When the system probes the
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.Em SCSI
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busses, it attaches any devices it finds to the appropriate
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drivers. If no driver seems appropriate, then it attaches the device to the
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uk (unknown) driver so that user level scsi ioctls may
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still be performed against the device.
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.Sh KERNEL CONFIGURATION
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The option SCSIDEBUG enables the debug ioctl.
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.Pp
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All devices and the SCSI busses support boot time allocation so that
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an upper number of devices and controllers does not need to be configured;
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.Em "device sd0"
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will suffice for any number of disk drivers.
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.Pp
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The devices are either
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.Em wired
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so they appear as a particular device unit or
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.Em counted
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so that they appear as the next available unused unit.
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.Pp
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To configure a driver in the kernel without wiring down the device use a
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config line similar to
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.Em "device ch0"
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to include the changer driver.
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.Pp
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To wire down a unit use a config line similar to
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.Em "device ch1 at scbus0 target 4 unit 0"
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to assign changer 1 as the changer with SCSI ID 4,
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SCSI logical unit 0 on SCSI bus 0.
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Individual scbuses can be wired down to specific controllers with
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a config line similar to
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.Em "controller scbus0 at ahc0"
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which assigns scsi bus 0 to the first unit using the ahc driver.
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For controllers supporting more than one bus,
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the particular bus can be specified as in
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.Em "controller scbus3 at ahc1 bus 1"
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which assigns scbus 1 to the second bus probed on the ahc1 device.
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.Pp
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When you have a mixture of wired down and counted devices then the
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counting begins with the first non-wired down unit for a particular
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type. That is, if you have a disk wired down as
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.Em "disk sd1" ,
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then the first non-wired disk shall come on line as
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.Em sd2 .
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.Sh IOCTLS
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There are a number of ioctls that work on any
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.Em SCSI
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device. They are defined in
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.Em sys/scsiio.h
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and can be applied against any scsi device that permits them.
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For the tape, it must be applied against the control
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device. See the manual page for each device type for more information about
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how generic scsi ioctls may be applied to a specific device.
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.Bl -tag -width DIOCSDINFO____
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.It Dv SCIOCRESET*
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reset a device.
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.It Dv SCIOCDEBUG
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Turn on debugging.. All scsi operations originating from this device's driver
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will be traced to the console, along with other information. Debugging is
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controlled by four bits, described in the header file. If no debugging is
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configured into the kernel, debugging will have no effect.
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.Em SCSI
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debugging is controlled by the configuration option
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.Em SCSIDEBUG.
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.It Dv SCIOCCOMMAND
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Take a scsi command and data from a user process and apply them to the scsi
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device. Return all status information and return data to the process. The
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ioctl will return a successful status even if the device rejected the
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command. As all status is returned to the user, it is up to the user
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process to examine this information to decide the success of the command.
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.It Dv SCIOCREPROBE
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Ask the system to probe the scsi busses for any new devices. If it finds
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any, they will be attached to the appropriate drivers. The search can be
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narrowed to a specific bus, target or lun. The new device may or may not
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be related to the device on which the ioctl was performed.
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.It Dv SCIOCIDENTIFY
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Ask the driver what it's bus, target and lun are.
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.It Dv SCIOCDECONFIG
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Ask the device to disappear. This may not happen if the device is in use.
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.El
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.Sh NOTES
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the generic scsi part of the system is still being mapped out.
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Watch this space for changes.
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.Pp
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A device by the name of su (scsi_user)
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(e.g su0-0-0) will map bus, target and lun to minor numbers. I have not
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yet decided yet whether this device will be able to open a device that is
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already controlled by an explicit driver.
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.Sh ADAPTERS
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The system allows common device drivers to work through many different
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types of adapters. The adapters take requests from the upper layers and do
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all IO between the
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.Em SCSI
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bus and the system. The maximum size of a transfer is governed by the
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adapter. Most adapters can transfer 64KB in a single operation, however
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many can transfer larger amounts.
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.Sh TARGET MODE
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Some adapters support
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.Em Target mode
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in which the system is capable of operating as a device, responding to
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operations initiated by another system. Target mode will be supported for
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some adapters, but is not yet complete for this version of the scsi system.
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.Sh FILES
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see other scsi device entries.
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.Sh DIAGNOSTICS
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When the kernel is compiled with option SCSIDEBUG, the SCIOCDEBUG ioctl
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can be used to enable various amounts of tracing information on any
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specific device. Devices not being traced will not produce trace information.
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The four bits that make up the debug level, each control certain types
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of debugging information.
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.Bl -tag -width THIS_WIDE_PLEASE
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.It Dv Bit 0
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Bit 0 shows all scsi bus operations including scsi commands,
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error information and the first 48 bytes of any data transferred.
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.It Dv Bit 1
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Bit 1 shows routines called.
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.It Dv Bit 2
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Bit 2 shows information about what branches are taken and often some
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of the return values of functions.
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.It Dv Bit 3
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Bit 3 shows more detailed information including DMA scatter-gather logs.
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.El
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.Sh SEE ALSO
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.Xr ch 4
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.Xr cd 4
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.Xr sd 4
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.Xr st 4
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.Xr uk 4
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.Xr su 4
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.Xr aha 4
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.Xr ahb 4
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.Xr bt 4
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.Xr uha 4
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.Sh HISTORY
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This
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.Nm
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system appeared in MACH 2.5 at TRW.
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