SCSI(4) BSD Programmer's Manual SCSI(4)NAMEscsi - scsi system
SYNOPSIS
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
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 does not need to be configured;
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
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 count-
ing 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 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 dev-
ice. 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 dev-
ices. If it finds any, they will be attached to the ap-
propriate 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 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.
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
operating as a device, responding to operations initiated by another sys-
tem. Target mode will be supported for some adapters, but is not yet com-
plete 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
specific 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 ALSOaac(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), gdt(4),
iha(4), intro(4), ioprbs(4), iopsp(4), isp(4), mpt(4), ncr(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), umass(4),
usscanner(4), vs(4), wds(4), wdsc(4), scsi(8)HISTORY
This scsi system appeared in MACH 2.5 at TRW.
MirOS BSD #10-current March 12, 2004 2
