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SD(4) NetBSD Kernel Interfaces Manual SD(4)
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by Kimmo Suominen.
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sd -- SCSI and ATAPI disk driver
sd* at scsibus? target ? lun ?
sd3 at scsibus0 target 3 lun 0
sd* at atapibus? drive ? flags 0x0000
The sd driver provides support for SCSI bus and Advanced Technology
Attachment Packet Interface (ATAPI) disks. 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).
Where the wd(4) device has a fairly low level interface to the system,
SCSI devices have a much higher level interface and talk to the system
via a SCSI host adapter (e.g., ahc(4)). A SCSI adapter must also be sep-
arately 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.
For the use of flags with ATAPI devices, see wd(4).
On many systems disklabel(8) is used to partition the drive into filesys-
tems. On some systems the NetBSD portion of the disk resides within a
native partition, and another program is used to create the NetBSD por-
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
The following config(1) options may be applied to SCSI disks as well as
to other disks.
SDRETRIES Set the number of retries that will be performed for oper-
ations it makes sense to retry (e.g., normal reads and
writes). The default is four (4).
SD_IO_TIMEOUT Set amount of time, in milliseconds, a normal read or
write is expected to take. The defaults is sixty seconds
(60000 milliseconds). This is used to set watchdog timers
in the SCSI HBA driver to catch commands that might have
died on the device.
The following ioctl(2) calls apply to SCSI disks as well as to other
disks. They are defined in the header file <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.
DIOCKLABEL Keep or drop the in-core disklabel on the last close.
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 car-
tridge previously locked. Used to prevent user and software
eject while the media is in use.
DIOCEJECT Eject the media cartridge from a removable device.
In addition, the scsi(4) general ioctl() commands may be used with the sd
driver, but only against the `c' (whole disk) partition.
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 accesses 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
/dev/sdup block mode SCSI disk unit u, partition p
/dev/rsdup raw mode SCSI disk unit u, partition p
ioctl(2), intro(4), scsi(4), wd(4), disklabel(5), disklabel(8), fdisk(8),
The sd driver was originally written for Mach 2.5, and was ported to
FreeBSD by Julian Elischer. It was later ported to NetBSD.
NetBSD 4.0 January 18, 1996 NetBSD 4.0