Specifications

Data Structures
1.10 Driver Prologue Table (DPT)
Table 1–12 Contents of Driver Prologue Table
Field Name Contents
DPT$L_FLINK* Forward link to next DPT. The driver-loading procedure writes this field.
The procedure links all DPTs in the system in a doubly linked list.
DPT$L_BLINK* Backward link to previous DPT. The driver-loading procedure writes this
field.
DPT$W_SIZE Size in bytes of the driver. The DPTAB macro writes this field by
subtracting the address of the beginning of the DPT from the address
specified as the end argument to the DPTAB macro. The driver-loading
procedure uses this value to determine the space needed in nonpaged
system memory to load the driver.
DPT$B_TYPE* Type of data structure. The DPTAB macro always writes the symbolic
constant DYN$C_DPT into this field.
DPT$B_REFC* Number of DDBs that refer to the driver. The driver-loading procedure
increments the value in this field each time the procedure creates another
DDB that points to the driver’s DDT.
DPT$B_ADPTYPE Type of adapter used by the devices using this driver. Every driver must
specify the string "UBA", "MBA", "GENBI", "NULL",or"DR" as the
value of the adapter argument to the DPTAB macro. Q22–bus drivers
should specify "UBA" as the adapter type. The macro writes the value
AT$_UBA, AT$_MBA, or AT$_GENBI in this field.
DPT$W_UCBSIZE Size in bytes of the unit control block for a device that uses this driver.
Every driver must specify a value for this field in the ucbsize argument to
the DPTAB macro.
The driver-loading procedure allocates blocks of nonpaged system memory
of the specified size when creating UCBs for devices associated with the
driver.
DPT$L_FLAGS Driver-loading flags. This field is also known as DPT$B_FLAGS. The
driver can specify any of a set of flags as the value of the flags argument to
the DPTAB macro. The driver-loading procedure modifies its loading and
reloading algorithm based on the settings of these flags.
Flags defined in the flag field include the following:
DPT$V_SUBCNTRL Device is a subcontroller.
DPT$V_SVP Device requires permanent system page to
be allocated during driver loading.
DPT$V_NOUNLOAD Driver cannot be reloaded.
DPT$V_SCS SCS code must be loaded with this driver.
DPT$V_DUSHADOW Driver is the shadowing disk class driver.
DPT$V_SCSCI Common SCS/CI subroutines must be
loaded with this driver.
DPT$V_BVPSUBS Common BVP subroutines must be loaded
with this driver.
DPT$V_UCODE Driver has an associated microcode image.
DPT$V_SMPMOD Driver has been designed to run in a
multiprocessing environment.
DPT$V_DECW_DECODE Driver is a decoding class driver.
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