SCSI(4) OpenBSD Programmer's Manual SCSI(4)NAME
scsi - scsi system
SYNOPSISscsibus at ...
cd* at scsibus?
ch* at scsibus?
safte* at scsibus?
sd* at scsibus?
ses* at scsibus?
st* at scsibus?
uk* at scsibus?
DESCRIPTION
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 buses, 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.
KERNEL CONFIGURATION
The option SCSIDEBUG enables the debug ioctl.
All devices and the SCSI buses support boot time allocation so that an
upper number of devices and controllers does not need to be configured;
sd* at scsibus? 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? 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 sd1 at scsibus?, 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
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.
SCIOCIDENTIFY Ask the driver what its bus, target and lun are. In
addition, the device type, ATAPI or SCSI, is returned.
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 I/O 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.
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
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 ALSOcd(4), ch(4), intro(4), safte(4), sd(4), ses(4), st(4), uk(4), scsi(8)HISTORY
This scsi system appeared in MACH 2.5 at TRW.
OpenBSD 4.9 July 3, 2010 OpenBSD 4.9
