.Cd "sd* at scsibus?"
.Cd "#sd0 at scsibus0 target 3 lun 0" Pq fixed-configuration example
DESCRIPTION
The
sd
driver provides support for a
SCSI
disk.
It allows the disk to be divided up into a set of pseudo devices called
partitions.
In general the interfaces are similar to those described by
wd(4).
SCSI
devices have a fairly high level interface to the system and talk to it via
a
SCSI
host adapter
(e.g.,
ahc(4/)).
A
SCSI
adapter must also be separately configured into the system
before a
SCSI
disk can be configured.
When the
SCSI
adapter is probed during boot, the
SCSI
bus is scanned for devices.
Any devices found which answer as
‘Direct’
type devices will be attached to the
sd
driver.
PARTITIONING
On many systems
disklabel(8)
is used to partition the drive into filesystems.
On some systems the
OpenBSD
portion of the disk resides within a native partition, and another
program is used to create the
OpenBSD
portion.
For example, the i386 port uses
fdisk(8)
to partition the disk into a BIOS level partition.
This allows sharing the disk with other operating systems.
IOCTLS
The following
ioctl(2)
calls apply to
SCSI
disks as well as to other disks.
They are defined in the header file
‹sys/disklabel.h›.
DIOCGDINFO
Read, from the kernel, the in-core copy of the disklabel for the
drive.
This may be a fictitious disklabel if the drive has never
been initialized, in which case it will contain information read
from the
SCSI
inquiry commands.
DIOCSDINFO
Give the driver a new disklabel to use.
The driver
will not
write the new
disklabel to the disk.
DIOCWLABEL
Enable or disable the driver's software
write protect of the disklabel on the disk.
DIOCWDINFO
Give the driver a new disklabel to use.
The driver
will
write the new disklabel to the disk.
DIOCLOCK
Lock the media cartridge into the device, or unlock a cartridge previously
locked.
Used to prevent user and software eject while the media is in use.
DIOCEJECT
Eject the media cartridge from a removable device.
DIOCINQ
Read the devices product information.
In addition, the
scsi(4)
general
ioctl();
commands may be used with the
sd
driver, but only against the
‘c’
(whole disk) partition.
NOTES
If a removable device is attached to the
sd
driver, then the act of changing the media will invalidate the
disklabel and information held within the kernel.
To avoid corruption, all access to the device will be discarded until there
are no more open file descriptors referencing the device.
During this period, all new open attempts will be rejected.
When no more open file descriptors reference the device, the first next
open will load a new set of parameters (including disklabel) for the drive.