scsi - scsi system
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 ?
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
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 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.
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
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 effect.
SCSI debugging is controlled by the
configuration
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
returned.
SCIOCDECONFIG Ask the device to disappear. This may not
happen if the
device is in use.
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.
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.
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 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.
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),
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)
This scsi system appeared in MACH 2.5 at TRW.
OpenBSD 3.6 March 12, 2004
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