ACPI: Advanced Configuration and Power Interface by Emma Jane Hogbin (bill gates best books TXT) 📕

ACPI: Advanced Configuration and Power Interface

Emma Jane Hogbin

[http://www.xtrinsic.com] xtrinsic

[email protected]

Erich Schubert - Author of the section on DSDT.

Revision History

Revision v1.5.1 2004-07-15 Revised by: ejh

Link included to the French translation of this document.

Revision v1.5 2004-05-21 Revised by: ejh

Minor updates for the 2.6.6 kernel and corrections regarding which kernels

need patching.

Revision v1.4 2004-05-12 Revised by: ejh

Initial thoughts on the 2.6.5 kernel; includes information on battery

monitoring applications causing touchpad lockup problems.

Outlines how to patch a kernel for ACPI support.

Table of Contents

About this document

Copyright and License

Translations

About ACPI

Why switch?

DSDT: Differentiated System Description Table

Installing from scratch

7.1. Choosing a kernel

Backups

Download and Unpack the New Kernel

9.1. Required packages

9.2. Unpack

Configure the new kernel

Compile the new kernel

Install the new kernel

Reboot and test

Load related modules

Switching from APM to ACPI

Using ACPI

References and Resources

Thanks

A. Patching Old Kernels

A.1. Getting the Source Files

B. ACPI the Non-Debian Way

B.1. Compile the kernel B.2. Install the new kernel B.3. Software packages

C. GNU Free Documentation License

C.1. PREAMBLE C.2. APPLICABILITY AND DEFINITIONS C.3. VERBATIM COPYING C.4. COPYING IN QUANTITY C.5. MODIFICATIONS C.6. COMBINING DOCUMENTS C.7. COLLECTIONS OF DOCUMENTS C.8. AGGREGATION WITH INDEPENDENT WORKS C.9. TRANSLATION C.10. TERMINATION C.11. FUTURE REVISIONS OF THIS LICENSE C.12. How to use this License for your documents About this document

When I first started the switch from APM to ACPI I didn't realize the kernel

needed to be patched. My problem (insanely loud fan) was fixed just by

upgrading to 2.4.20 (Debian packaged kernel with an earlier patch from [http://acpi.sourceforge.net] acpi.sourceforge.net). Unfortunately after the first

upgrade I wasn't able to halt my computer without using the power switch to

power-down my computer. It wasn't until later that I realized I had an old,

ineffectual ACPI patch. This HOWTO was written to summarize the install

process for myself, and hopefully help others who are also having a hard time

finding information about ACPI. Please note: the main article outlines [http:

//www.debian.org] The Debian Way of doing things. There is also generic

information in the Appendix B for those of you who prefer ... the generic

way.

Copyright and License

Copyright (c) 2003, 2004 Emma Jane Hogbin.

Permission is granted to copy, distribute and/or modify this document

under the terms of the GNU Free Documentation License, Version 1.1 or any

later version published by the Free Software Foundation; with no

Invariant Sections, no Front-Cover Texts, and with no Back-Cover Texts. A

copy of the license is included in Appendix C.

Translations

This document is also available in the following languages:

* English version 1.2 translated to: [http://www.traduc.org/docs/HOWTO/lecture/ACPI-HOWTO.html] Francais. Merci a Guillaume Lelarge et Vanessa

Conchodon pour le traduction! About ACPI

In the world of power management ACPI is relatively new to the game. It was

first released in 1996 by Compaq/Hewlett-Packard, Intel, Microsoft, Phoenix

and Toshiba. These developers aimed to replace the previous industry standard

for power management. Their [http://www.acpi.info] ACPI.info site contains

the official specifications, a list of companies that support ACPI and a

number of other goodies. This is definitely not required reading, but may be

of some interest to the insanely curious.

ACPI allows control of power management from within the operating system. The

previous industry standard for power management, Advanced Power Management

(APM), is controlled at the BIOS level. APM is activated when the system

becomes idle--the longer the system idles, the less power it consumes (e.g.

screen saver vs. sleep vs. suspend). In APM, the operating system has no

knowledge of when the system will change power states.

ACPI can typically be configured from within the operating system. This is

unlike APM where configuration often involves rebooting and entering the BIOS

configuration screens to set parameters.

ACPI has several different software components:

* a subsystem which controls hardware states and functions that may have

previously been in the BIOS configuration These states include: + thermal control + motherboard configuration + power states (sleep, suspend)

* a policy manager, which is software that sits on top of the operating

system and allows user input on the system policies

* the ACPI also has device drivers that control/monitor devices such as a

laptop battery, SMBus (communication/transmission path) and EC (embedded controller).

If you would like more information on power management in laptops, check out

the resources on [http://www.tuxmobil.org] tuxmobil.org. Specifically: Power

Management with Linux - APM, ACPI, PMU and the [http://tuxmobil.org/

Mobile-Guide.db/mobile-guide-p2c1-hardware-in-detail.html] Hardware in Detail

section of the Linux Mobile Guide.

Why switch?

Not all systems support both APM and ACPI. I switched because my system only

supported ACPI. Pretty easy decision really. If you're switching to get

[http://acpi.sourceforge.net/documentation/sleep.html] S3 (suspend to RAM)

support and you're using a 2.4.x kernel, don't bother. It is [http://

lists.debian.org/debian-laptop/2003/debian-laptop-200304/msg00418.html] not

supported. Period.

Not sure if your system is supported? ACPI4Linux has a list of supported

machines/BIOSes started on their Wiki. Please contribute to the list if

you've installed ACPI! They also have a list of machines that are [http://

acpi.sourceforge.net/documentation/blacklist.html] not supported.

For more information about the power management in laptops you may (also)

find the [http://www.tldp.org/HOWTO/mini/Battery-Powered/index.html] Battery

Powered Linux Mini-HOWTO useful.

DSDT: Differentiated System Description Table

Thanks to [http://www.vitavonni.de/] Erich writing this section.

You might need to override the DSDT when certain features like battery status

are incorrectly reported (usually causing error messages to syslog). DELL

laptops usually need this kind of override. Fixed DSDT for many systems are

available on the [http://acpi.sourceforge.net/dsdt/index.php] DSDT page,

along with a patch that tells the kernel to ignore the BIOS-supplied table

but use the compiled-in fixed DSDT.

Basically you need to copy the fixed table into your kernel source with a

special filename (or modifying the filename in the patch supplied at the

[http://acpi.sourceforge.net/dsdt/index.php] DSDT page) This override is

quite easy: instead of loading the DSDT table from bios, the kernel uses the

compiled-in DSDT table. That's all.

Installing from scratch

ACPI is constantly being revised. It is available in later versions of the

2.4.x series kernel (2.4.22 and higher), and all 2.6.x series kernels. If you

would like to use a kernel before 2.4.22, you will need to patch your kernel

source to add ACPI functionality. If at all possible you should use the

latest stable version of the kernel. Patches are available from [http://

acpi.sourceforge.net] acpi.sourceforge.net.

Red Hat Fedora Core 2 now ships with ACPI enabled by default! This is big

progress for the ACPI development team. Congratulations to everyone.

Note Even the latest kernel will sometimes have minor bug fixes available as

a patch. You should check the ACPI4Linux web site to see if there are any patches available.

You need to get the patch that exactly matches the version of the kernel

that you are running. Since this is the "install from scratch" section I will

assume you know exactly which kernel you will be installing.

7.1. Choosing a kernel

This document was originally written for the 2.4.20 kernel and has been

updated since to include information about the 2.6.x series kernels. At the

time of this update the 2.6.x series kernels are proving easy for some and

harder for others. (I personally cannot properly power down my computer with

the 2.6.5 kernel.)

If you can, I would recommend waiting to upgrade your kernel to the 2.6.x

series until more bugs are ironed out. There are a lot of changes in the

2.6.x series kernel. When I upgraded to 2.6.5 to update this document I ran

into problems with my wireless connection, my nvidia graphics card, and with

ACPI. Your mileage may vary. I personally had good success with the 2.4.20

with the latest patch and the 2.4.22 kernel with no patch. A Google through

your distribution's mailing list, and the acpi-devel mailing list should help

you to pick the right kernel.

Note This document uses the 2.4.20 kernel as an example for 2.4.x series

kernels. Substitute your own kernel version as appropriate.

Regardless of which kernel you choose, if it is a kernel that requires

patching, it is important to use the latest version of the ACPI patch. Some

distributions have already patched their kernels. This is the case for

Debian, and may be the case for others. For more information on the patches

that have been applied to the Debian kernel source package scan through: /usr

/src/kernel-source-/README.Debian. If you are not using Debian you

will probably still be able to find an equivalent file for your distribution.

A user on acpi-support confirmed that I shouldn't need any of the additional

patches that have been applied to the kernel to run my laptop. If you are

running a production-level server and/or are serving web pages to the

internet, you should really apply any additional security patches.

Warning If a kernel has had other patches applied to it, you may have

problems applying the ACPI patch. Of course, an ACPI patch should not be applied to a kernel that is already patched for ACPI. As long as there has not been an ACPI patch applied to the kernel it should be possible to apply one now. Depending on the patches applied, you may need to modify some of the Makefiles for your patch to be successful. This is beyond my current grasp of reality so it is not covered in this document.

7.1.1. Debian-ized pre-patched kernel

If you would prefer to use a Debian-ized kernel instead of a fresh one,

[http://people.debian.org/~maxx] maxx has provided a pre-patched

kernel-source package