2002 FREENIX Track Technical Program - Abstract
ACPI implementation on FreeBSD
Takanori Watanabe, Kobe University
Prior to the introduction of the Advanced Configuration and Power
Management Interface (ACPI), PCs did not have a unified standard
mechanism that allowed the operating system to enumerate, configure,
and manage the power usage and thermal properties of built-in hardware
devices. Instead, these devices were either left unmanaged, or they
were managed by special BIOS-level code such as Plug-and-Play BIOS
(PnP BIOS), Advanced Power Management BIOS (APM), or other
vendor-specific BIOS code. These firmware-driven methods increase
firmware costs, and the resulting BIOS code is difficult to alter or
debug. Device management issues are becoming more important,
especially in moble computing environments where fine-grain power
management is often necessary. ACPI replaces PnP BIOS, APM, and a
number of ad hoc methods while providing a management framework that
allows increased flexibility in hardware design. Unfortunately, the
increased power and flexibility of ACPI comes with a cost: it requires
substantial software support from the operating system kernel. In
this paper we describe ACPI, how it is implemented in FreeBSD, and the
lessons we learned from working with ACPI.
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