Specifications

Data Structures
1.9 Driver Dispatch Table (DDT)
Table 1–11 (Cont.) Contents of Driver Dispatch Table
Field Name Contents
DDT$L_MNTVER Address of the system routine (IOC$MNTVER) called at the beginning and
end of mount verification operation. The mntver argument to the DPTAB
macro defaults to this routine. Use of the mntver argument to call any
routine other than IOC$MNTVER is reserved to Digital.
DDT$L_CLONEDUCB Address of routine to call when UCB is cloned.
DDT$W_FDTSIZE* Number of bytes in FDT. The driver-loading procedure uses this field to
relocate addresses in the FDT to system virtual addresses.
DDT$L_MNTV_SSSC* Address of routine to call when performing mount verification for a shadow-
set state change. Use of this field is reserved to Digital.
DDT$L_MNTV_FOR* Address of routine to call when performing mount verification for a foreign
device. Use of this field is reserved to Digital.
DDT$L_MNTV_SQD* Address of routine to call when performing mount verification for a
sequential device. Use of this field is reserved to Digital.
DDT$L_AUX_STORAGE* Address of auxiliary storage area. Use of this field is reserved to Digital.
DDT$L_AUX_ROUTINE* Address of auxiliary routine. Use of this field is reserved to Digital.
DDT$L_CHANNEL_
ASSIGN*
Address of routine to call from $ASSIGN.
DDT$L_CANCEL_
SELECTIVE*
Address of selective cancel I/O entry point.
1.10 Driver Prologue Table (DPT)
When loading a device driver and its database into virtual memory, the driver-
loading procedure finds the basic description of the driver and its device in a
driver prologue table (DPT). The DPT provides the length, name, adapter type,
and loading and reloading specifications for the driver.
A device driver creates a DPT by invoking the system macros DPTAB and DPT_
STORE. The driver prologue table is illustrated in Figure 1–13 and described in
Table 1–12.
Figure 1–13 Driver Prologue Table (DPT)
DPT$L_FLINK* 0
DPT$L_BLINK* 4
DPT$W_SIZEDPT$B_TYPE*DPT$B_REFC* 8
DPT$B_ADPTYPEUnusedDPT$W_UCBSIZE 12
DPT$L_FLAGS 16
DPT$W_INITTABDPT$W_REINITTAB 20
DPT$W_UNLOADDPT$W_MAXUNITS 24
(continued on next page)
1–38