On VAX
systems, the System Generation utility (SYSGEN) loads the generic
SCSI class driver into system virtual memory, creates additional data
structures for the device unit, and calls the driver's controller
initialization routine and unit initialization routine. SYSGEN automatically
loads and autoconfigures the SCSI port driver at system initialization.
As part of autoconfiguration, SYSGEN polls each device on each SCSI
bus. If the device identifies itself as a direct-access device, direct-access
CD-ROM device, or flexible disk device, SYSGEN automatically loads
the disk class driver (DKDRIVER). If the device identifies itself
as a sequential-access device, SYSGEN automatically loads the tape
class driver (MKDRIVER). If the autoconfiguration facility does not
recognize the type of the SCSI device, it does not load a driver.
If a third-party-supplied SCSI device requires
that the generic class driver be loaded, it must be configured by
an explicit SYSGEN CONNECT command, as follows:
$ RUN SYS$SYSTEM:SYSGEN
SYSGEN> CONNECT GKpd0u /NOADAPTER |
SYSMAN performs the same functions that SYSGEN
performs on VAX systems. If a third-party-supplied SCSI device requires
that the generic class driver be loaded, the device must be configured
by an explicit SYSMAN CONNECT command, as follows:
$ RUN SYS$SYSTEM:SYSMAN
SYSMAN> IO CONNECT GKpd0u /NOADAPTER/DRIVER=SYS$GKDRIVER |
On VAX and Alpha systems, GK is the device mnemonic for the generic SCSI class driver (GKDRIVER); p represents the SCSI port ID (for instance, the controller
ID A or B ); d represents the SCSI device ID (a digit from 0 to 7); 0 signifies
the digit zero; and u represents the SCSI logical
unit number (a digit from 0 to 7).
Multiple devices residing on any SCSI bus in the
system can share GKDRIVER as a class driver, as long as a CONNECT
command is issued for each target device that requires the driver.
Because just one connection can exist through
the SCSI port driver to each target, the generic class driver cannot
be used for a target if a different SCSI class driver is already connected
to that target. For example, if the SCSI disk class driver has a connection
to device ID 2 on the SCSI bus identified by SCSI port ID B (DKB200), the generic class driver cannot be used to
communicate with this disk. An attempt to connect GKDRIVER for this
target results in GKB200 being placed off line.
