Specifications

Data Structures
Notes
Driver code must consider fields marked by asterisks (*) to be read-only
fields. Fields marked ‘‘Reserved’’ or ‘‘Unused’’ are reserved for future use
by Digital unless otherwise specified.
When referring to locations within a data structure, a driver should
use symbolic offsets, never numeric offsets, from the beginning of the
structure. Numeric offsets are likely to change with each new release of
the operating system. The figures in this chapter list numeric offsets only
as an aid in driver debugging.
Figure 1–1 I/O Database
ZK−1766−GE
FDT Routine
Driver
Start I/O Routine
Driver
Routine
Interrupt Service
Driver
registers
Device
controller)
(synchronizes
CRB
device)
(describes
UCB
to device)
logical path
(describes
CCB
request)
I/O
(describes
Packet
Request
I/O
controller)
(describes
IDB
DDB
adapter)
(describes
ADP
process
requesting
describes
Block
Control
Process
Routine
Controller Initialization
Driver
(locates
DDT
(
)
for device
(
type)
driver)
1–2