DCD(7) DCD(7)
NAME
DCD - Direct-Coupled Disk host adapter Subsystem
DESCRIPTION
The DCD subsystem consists of at least one DCD Host Controller
card which has at least one logical unit attached to it.
The DCD subsystem adds support for non-SCSI devices under SDI
for use with related target drivers. This subsystem is
accessed indirectly by opening an appropriate target driver to
access a target device that is on a DCD controller.
It is also possible to access this subsystem via the pass-
through driver. To find the appropriate device to use, while
the device is being accessed through the target driver, use
the B_GETDEV ioctl to get the major and minor numbers of the
pass-though node. This node may either be created and/or open
for use.
ioctl Calls
There are four groups of ioctl(2) commands supported by DCD .
The first group contains the ioctl commands used by the DCD
driver itself.
SDI_SEND Used to send a pass through command to a target
controller bypassing the associated target
driver.
SDI_BRESET Used to reset the bus.
HA_VER For a 80386-based computer, used to determine
the Driver Interface Version supported by the
driver. It returns the structure ver_no
defined in sdi.h.
The second group is used by the driver and all target drivers
that use the SCSI Driver Interface protocol to communicate
with their associated target controllers.
B_GETTYPE Return the bus name (DCD) and device driver
name of a specific device.
The third group should be used by all the target drivers that
use the SCSI Driver Interface protocol to communicate with
their associated target controllers. This ioctl is not
supported by the DCD driver.
Copyright 1994 Novell, Inc. Page 1
DCD(7) DCD(7)
B_GETDEV Return the pass through major and minor numbers
to the calling utility to allow creation of a
pass through the special device file.
The fourth group should be used to get and set device
geometry. These return or accept the structure dsk_geom
defined in sdi.h.
HA_GETPARMS Return Host adapters idea of the device
geometry. This is what the system uses during
the boot sequence. This is used by certain
target drivers.
HA_SETPARMS Set the Host adapters idea of the device
geometry. Note that some Host adapters do not
support this ioctl and will result in an error.
HA_GETPPARMS Return the actual device geometry. This is the
actual as opposed to virtual device geometry.
The DCD driver has a halt routine that is executed during
shutdown, which allows the controller enough time to flush the
disk cache (if present) to disk. Although two seconds are
allowed for this flush, the actual timeout value is an
external variable in the DCD space.c file. You can modify
this variable if a specific controller needs more time to
clear the cache.
Files
/usr/include/sys/sdi.h
/usr/include/sys/sdi_edt.h
REFERENCES
ioctl(2)
Copyright 1994 Novell, Inc. Page 2