Managing and Developing Dynamically Loadable Kernel Modules

Developing Dynamically Loadable Kernel Modules

Chapter 12 525

Developing Dynamically Loadable Kernel

Modules

This section explains the process ofwriting modules in the DLKM format

and provides background information speciﬁc to device driver

development. It focuses on the writing and installation of loadable device

drivers because they constitute the majority of supported DLKM

modules for HP-UX 11.0 and later releases.

This section is intended primarily for programmers who want to write

DLKM modules and/or convert existing static (non-loadable) modules to

the DLKM format. It is assumed that the reader has a good

understanding of the HP-UX operating system, the C programming

language, and the writing and testing of static device drivers.

Since kernel modules written to the DLKM speciﬁcation can either be

conﬁgured as dynamically loadable or statically linked, device driver

developers must write their DLKM modules to accommodate either

conﬁguration.

Writing modules in the DLKM format requires writing additional

module initialization code called wrapper code, which enables the DLKM

infrastructure to logically connect and disconnect a loadable module to

and from the running kernel. Existing traditional device drivers that are

going to be conﬁgured into the system as loadable modules must be

converted to the DLKM format, and must be re-packaged according to

the module packaging architecture introduced in HP-UX 11.0.

NOTE For Itanium-based systems, boot time loading during phase BOOT1 is

available for miscellaneous modules only. For phase BOOT2, other

supported module types such as WSIO and Streams drivers may be

loaded.

This section covers the following topics:

❏ “Overview of Boot Time Loading” on page 526 explains the use of

loadable modules during the boot sequence.

❏ “Module Component Files” on page 529 identiﬁes and describes the

ﬁle set that makes up a DLKM, which consists of the module’s object