SCSI(4)                   OpenBSD Programmer's Manual                  SCSI(4)

NAME
     scsi - scsi system

SYNOPSIS
     scsibus* at aha?
     scsibus* at ncr?
     device cd* at scsibus? target ? lun ?
     device ch* at scsibus? target ? lun ?
     device sd* at scsibus? target ? lun ?
     device st* at scsibus? target ? lun ?
     device ss* at scsibus? target ? lun ?
     device su* at scsibus? target ? lun ?
     device uk* at scsibus? target ? lun ?

DESCRIPTION
     The scsi system provides a uniform and modular system for the implementa-
     tion of drivers to control various scsi devices, and to utilize different
     scsi host adapters through host adapter drivers. When the system probes
     the SCSI busses, it attaches any devices it finds to the appropriate
     drivers. If no driver seems appropriate, then it attaches the device to
     the uk (unknown) driver so that user level scsi ioctls may still be per-
     formed against the device.

KERNEL CONFIGURATION
     The option SCSIDEBUG enables the debug ioctl.

     All devices and the SCSI busses support boot time allocation so that an
     upper number of devices and controllers do not need to be configured;
     device sd* at scsibus? target ? lun ? will suffice for any number of disk
     drivers.

     The devices are either wired so they appear as a particular device unit
     or counted so that they appear as the next available unused unit.

     To configure a driver in the kernel without wiring down the device use a
     config line similar to device ch* at scsibus? target ? lun ? to include
     the changer driver.

     To wire down a unit use a config line similar to device ch1 at scsibus0
     target 4 lun 0 to assign changer 1 as the changer with SCSI ID 4, SCSI
     logical unit 0 on SCSI bus 0.  Individual scsibuses can be wired down to
     specific controllers with a config line similar to scsibus0 at ahc0 which
     assigns scsi bus 0 to the first unit using the ahc driver.  For con-
     trollers supporting more than one bus, the particular bus can be speci-
     fied as in scsibus3 at ahc1 bus 1 which assigns scsibus 1 to the second
     bus probed on the ahc1 device.

     When you have a mixture of wired down and counted devices then the count-
     ing begins with the first non-wired down unit for a particular type.
     That is, if you have a disk wired down as disk sd1 at scsibus? target ?
     lun ?, then the first non-wired disk shall come on line as sd2.

IOCTLS
     There are a number of ioctls that work on any SCSI device. They are de-
     fined in sys/scsiio.h and can be applied against any scsi device that
     permits them.  For the tape, it must be applied against the control de-
     vice. See the manual page for each device type for more information about
     how generic scsi ioctls may be applied to a specific device.

     SCIOCRESET*     reset a device.

     SCIOCDEBUG      Turn on debugging.. All scsi operations originating from
                     this device's driver will be traced to the console, along
                     with other information. Debugging is controlled by four
                     bits, described in the header file. If no debugging is
                     configured into the kernel, debugging will have no ef-
                     fect.  SCSI debugging is controlled by the configuration
                     option SCSIDEBUG.

     SCIOCCOMMAND    Take a scsi command and data from a user process and ap-
                     ply them to the scsi device. Return all status informa-
                     tion and return data to the process. The ioctl will re-
                     turn a successful status even if the device rejected the
                     command. As all status is returned to the user, it is up
                     to the user process to examine this information to decide
                     the success of the command.

     SCIOCREPROBE    Ask the system to probe the scsi busses for any new de-
                     vices. If it finds any, they will be attached to the ap-
                     propriate drivers. The search can be narrowed to a spe-
                     cific bus, target or lun. The new device may or may not
                     be related to the device on which the ioctl was per-
                     formed.

     SCIOCIDENTIFY   Ask the driver what its bus, target and lun are. In addi-
                     tion, the device type, ATAPI or SCSI, is returned.

     SCIOCDECONFIG   Ask the device to disappear. This may not happen if the
                     device is in use.

NOTES
     The generic scsi part of the system is still being mapped out.  Watch
     this space for changes.

     A device by the name of su (scsi_user) (e.g. su0-0-0) will map bus, tar-
     get and lun to minor numbers. It has not yet been decided whether this
     device will be able to open a device that is already controlled by an ex-
     plicit driver.

ADAPTERS
     The system allows common device drivers to work through many different
     types of adapters. The adapters take requests from the upper layers and
     do all IO between the SCSI bus and the system. The maximum size of a
     transfer is governed by the adapter. Most adapters can transfer 64KB in a
     single operation, and many can transfer larger amounts.

TARGET MODE
     Some adapters support target mode in which the system is capable of oper-
     ating as a device, responding to operations initiated by another system.
     Target mode will be supported for some adapters, but is not yet complete
     for this version of the scsi system.

DIAGNOSTICS
     When the kernel is compiled with option SCSIDEBUG, the SCIOCDEBUG ioctl
     can be used to enable various amounts of tracing information on any spe-
     cific device. Devices not being traced will not produce trace informa-
     tion.  The four bits that make up the debug level each control certain
     types of debugging information.

     Bit 0  shows all scsi bus operations including scsi commands, error in-
            formation and the first 48 bytes of any data transferred.

     Bit 1  shows routines called.

     Bit 2  shows information about what branches are taken and often some of
            the return values of functions.

     Bit 3  shows more detailed information including DMA scatter-gather logs.

SEE ALSO
     cd(4), ch(4), sd(4), ss(4), st(4), uk(4)

HISTORY
     This scsi A system appeared in MACH 2.5 at TRW.

OpenBSD 2.9                     August 4, 1996                               3
