Specifications

Device Driver Entry Points

Unit Initialization Routine

Prepares a device for operation and, in the case of a device on a dedicated

controller, initializes the controller.

Speciﬁed in

You can specify a unit initialization routine in two ways, either of which will

sufﬁce for all but a few speciﬁc devices.

• Specify the address of the unit initialization routine unitinit argument of the

DDTAB macro. This macro places the address of the routine into DDT$L_

UNITINIT. MASSBUS device drivers must use this method.

• Use the DPT_STORE macro to place the address of the unit initialization

routine into CRB$L_INTD+VEC$L_UNITINIT.

Called by

The System Generation utility (SYSGEN) calls a driver’s unit initialization

routine when processing a CONNECT command. The operating system calls a

unit initialization routine when the device, the controller, the processor, or the

adapter to which the device is connected undergoes power failure recovery.

Synchronization

The operating system calls a unit initialization routine at IPL$_POWER. If

it must lower IPL, the controller initialization routine cannot explicitly do so.

Rather, it must fork. Because SYSGEN calls the unit initialization routine

immediately after the controller initialization returns control to it, the driver’s

initialization routines must synchronize their activities. If the controller

initialization routine forks, the unit initialization routine must be prepared

to execute before the controller initialization routine completes.

The portion of the unit initialization that services power failure cannot acquire

any spinlocks. As a result, the routine cannot fork to perform power failure

servicing.

Context

Because the operating system calls it in system context, a unit initialization

routine can only refer to those virtual addresses that reside in system (S0) space.

A unit initialization routine must preserve the contents of all registers except R0,

R1, and R2.

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