scsi,
scsibus —
SCSI system
cd* at scsibus?
ch* at scsibus?
safte* at scsibus?
sd* at scsibus?
ses* at scsibus?
st* at scsibus?
uk* at scsibus?
# multipath support
emc* at scsibus?
hds* at scsibus?
rdac* at scsibus?
sym* at scsibus?
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.
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.
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
int *- 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
scsireq_t *- 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
struct scsi_addr *- Ask the driver what its bus, target and lun are. In addition, the device
type, ATAPI or SCSI, is returned.
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.
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.
cd(4),
ch(4),
emc(4),
hds(4),
intro(4),
mpath(4),
rdac(4),
safte(4),
sd(4),
ses(4),
st(4),
sym(4),
uk(4),
scsi(8)
This
scsi system appeared in MACH 2.5 at
TRW.
![[OpenBSD]](/openbsd.gif){kind=small}