Managing and Developing Dynamically Loadable Kernel Modules

Developing Dynamically Loadable Kernel Modules

Chapter 12528

Module dependency

If a module requires another module in order to work properly, you can

specify a dependency between them. The module loader attempts to load

all the dependent modules when it ﬁnds dependencies during loading of

a module. This module dependency mechanism is also applicable to Boot

Time Loading.

For the system to work properly, the module developer or system

administrator needs to exercise care in determining the conﬁgured

loading phase and the supported loading phase of modules. A module

without BOOT1 or BOOT2 speciﬁed in its supported loading phase would

not be registered during boot phase 1 or boot phase 2. Such modules

cannot be loaded in those phases even if they are deﬁned as dependents

of other boot-time-loaded modules. A module loading failure in boot time

may be critical for your system if the failed module provides essential

functionality for your system (i.e., SCSI disk driver).

If there is a possibility that the module will be referred to as a dependent

during boot time, then the module must include BOOT1 or BOOT2 in the

supported loading phase speciﬁcation.

Module Registration

All modules that have BOOT1 in their supported loading phase

speciﬁcation are registered in system boot phase 1. All other modules are

registered during boot phase 2, regardless of the values speciﬁed in their

supported loading phase.

NOTE Only miscellaneous modules (MISC) can be registered during boot phase

1 on Itanium-based systems. Other DLKM types supportedin HP-UX 11i

Version 1.5 will not work properly in early boot. When their type-speciﬁc

registration is performed, the needed functionality will not be available

during the early phases of booting, (i.e., streams, wsio, etc.).

Module Loading

A module having a conﬁgured loading phase of BOOT1 will be loaded just

after DLKM has initialized in boot phase 1. This is later than

initialization steps for spinlocks and the primitive memory allocation

method used by boot phase 1, but prior to beginning I/O initialization.