Managing and Developing Dynamically Loadable Kernel Modules

Developing Dynamically Loadable Kernel Modules

Chapter 12526

ﬁle and other conﬁguration ﬁles needed to install the module into the

system.

❏ “Initializing and Terminating DLKM Modules” on page 538 describes

the steps that each type of DLKM module must take to initialize and

terminate itself.

❏ “DLKM Module Development Process” on page 551 describes the

iterative processes and procedures that are of speciﬁc interest to

developers of new DLKM modules, such as writing the module, and

installing, testing and debugging it. Other procedures useful in the

development process, such as conﬁguring, registering, and loading a

DLKM, are covered in the section “Managing Dynamically Loadable

Kernel Modules” on page 493 of this chapter.

❏ “Sample DLKM WSIO Class Driver” on page 558, presents a

complete skeleton of a DLKM WSIO (Workstation Input/Output)

class driver in HP-UX.

Overview of Boot Time Loading

Dynamically Loadable Kernel Modules were introduced in HP-UX 11.0.

This feature allowed kernel modules to be loaded or unloaded

dynamically without rebooting. However, loading and unloading of

modules was allowed only during system run-time. This prevented very

low-level kernel functions that are needed at early system boot from

being implemented as DLKM modules.

With this release the Boot Time Loading feature eliminates this

limitation for the Itanium-based platform. The HP-UX boot process can

be divided into two parts, the architecture-dependent part and the

architecture-independent part. The architecture-dependent part is

referred to as the boot phase 1, and the architecture-independent part is

referred to as boot phase 2. More precisely, boot phase 1 is the time when

the kernel does not use pfdat (virtual memory page management table)

based memory allocation system, and boot phase 2 is the time when the

kernel begins to use the regular virtual memory allocation system that is

used during system run-time

When you conﬁgure a module to be loaded during boot time, it is

necessary to specify the phase in which you want to load the module. A

module can specify two kinds of loading phases: “conﬁgured loading

phase” and “supported loading phase.”

The supported loading phase speciﬁes the capability of a module to be