Specifications

Writing Device-Driver Tables
4.1 Driver Prologue Table
• Code identifying the device by its adapter type in the adapter argument.
You can supply any name that, when appended to the string "AT$_", results
in a symbol defined by the $DCDEF macro in SYS$LIBRARY:STARLET.MLB.
Of these symbols, the driver-loading procedure takes special action only
when the keyword NULL is present. The driver-loading procedure creates
no ADP for a null adapter (AT$_NULL) and clears the VEC$PS_ADP and
IDB$L_ADP fields.
• Size of the unit control block (UCB) in the ucbsize argument.
The DPTAB also allows you to specify the following information, if applicable to
the device driver:
• Whether the driver needs a permanently allocated system page
• Whether the driver needs controller register access mailboxes (CRAMs) to be
preallocated and associated with the unit control block (UCB) or interrupt
dispatch block (IDB).
• Maximum number of units supported by the driver (default is 8)
• Number of UCBs to be created when the driver is loaded by means of the
System Management (SYSMAN) utility’s autoconfiguration facility and the
address of a unit delivery routine to be called by that facility
A driver typically follows the DPTAB macro invocation with several instances
of the DPT_STORE macro and the DPT_STORE_ISR macro, which allow the
driver to communicate its initialization needs to the driver-loading procedure and
reloading procedures. A driver uses these macros in the following manner:
• A driver invokes the DPT_STORE macro once, specifying the INIT keyword,
to automatically generate a driver I/O database initialization routine. This
routine, which executes when the driver is first loaded into the system,
initializes those fields specified by the series of DPT_STORE macros that
intervene between the DPT_STORE INIT and DPT_STORE REINIT
declarations.
Drivers use the DPT_STORE macro with the INIT table marker label to
begin a list of DPT_STORE invocations that supply initialization data for the
following fields:
UCB$B_FLCK Index of the fork lock under which the driver performs
fork processing. Fork lock indexes are defined by the
$SPLCODDEF definition macro (invoked by DPTAB) as
follows:
IPL Fork Lock Index
8 SPL$C_IOLOCK8
9 SPL$C_IOLOCK9
10 SPL$C_IOLOCK10
11 SPL$C_IOLOCK11
UCB$B_DIPL Device interrupt priority level
Other commonly initialized fields are as follows:
UCB$L_DEVCHAR Device characteristics
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