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NAME    [Toc]    [Back]

     scsi - scsi system

SYNOPSIS    [Toc]    [Back]

     scsibus at ...

     cd* at scsibus? target ? lun ?
     ch* at scsibus? target ? lun ?
     sd* at scsibus? target ? lun ?
     st* at scsibus? target ? lun ?
     ss* at scsibus? target ? lun ?
     uk* at scsibus? target ? lun ?

     ses* at scsibus? target ? lun ?

DESCRIPTION    [Toc]    [Back]

     The SCSI system provides a uniform and  modular  system  for
the implementation
 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 performed
 against the device.


     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 does not need to be
     sd* at scsibus? target ? lun ?  will suffice for any  number
of disk

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

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

     To wire down a unit use a config line similar to
     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  controllers supporting more than one bus, the
particular bus
     can be specified as in
     scsibus3 at ahc1 bus 1 which assigns scsibus 1 to the second
bus probed
     on the ahc1 device.

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

IOCTLS    [Toc]    [Back]

     There are a number of ioctls that work on any  SCSI  device.
They are defined
  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 device.
  See the manual page for each device type for more information
     about how generic scsi ioctls may be applied to  a  specific

     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 effect.
  SCSI debugging is controlled  by  the
                     option SCSIDEBUG.

     SCIOCCOMMAND     Take  a  scsi  command and data from a user
process and apply
 them to the  scsi  device.   Return  all
status information
  and  return  data to the process.  The
ioctl will return
 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 devices.
  If it finds any, they  will  be  attached to the appropriate
  drivers.   The search can be narrowed to a specific
 bus, target or lun.   The  new  device
may or may not
                     be  related to the device on which the ioctl
was performed.

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

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

ADAPTERS    [Toc]    [Back]

     The system allows common device drivers to work through many
     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    [Toc]    [Back]

     Some adapters support target mode in which the system is capable of operating
 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    [Toc]    [Back]

     When the kernel  is  compiled  with  option  SCSIDEBUG,  the
     can be used to enable various amounts of tracing information
on any specific
 device.  Devices not being  traced  will  not  produce
trace information.
   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 information
  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    [Toc]    [Back]

     aac(4), adv(4),  adw(4),  aha(4),  ahb(4),  ahc(4),  aic(4),
ami(4), asc(4),
     atapiscsi(4),  bha(4), cac(4), cd(4), ch(4), dpt(4), esp(4),
     iha(4),  intro(4),  ioprbs(4),  iopsp(4),  isp(4),   mpt(4),
     ncrscsi(4),  oosiop(4),  osiop(4),  pcscp(4), sd(4), sea(4),
ses(4), si(4),
     siop(4), ss(4), ssh(4), st(4), sw(4), trm(4), twe(4), uk(4),
     usscanner(4), vs(4), wds(4), wdsc(4), scsi(8)

HISTORY    [Toc]    [Back]

     This scsi system appeared in MACH 2.5 at TRW.

OpenBSD      3.6                          March      12,     2004
[ Back ]
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