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 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 The Debian Way of doing things. There is also generic information in the Appendix A for those of you who prefer ... the generic way.
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 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:
If you would like more information on power management in laptops, check out the resources on tuxmobil.org. Specifically: Power Management with Linux - APM, ACPI, PMU and the Hardware in Detail section of the Linux Mobile Guide.
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 S3 (suspend to RAM) support and you're using a 2.4.x kernel, don't bother. It is 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 not supported.
Thanks to 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 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 modifing the filename in the patch supplied at the 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.
ACPI is constantly being revised. It is currently not available in the 2.4.x series kernels but will be released into the 2.5.x version kernels (or possibly not until 2.6). This means all kernels released before 2.5.x must be patched. The patches are available from acpi.sourceforge.net. 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.
This document was written for the 2.4.20 kernel. Since that time the 2.4.21 kernel has been released as the latest stable kernel. There have been mixed levels of success with 2.4.21 and the latest ACPI patch. For now I recommend sticking to the 2.4.20 kernel and its latest patch: 2002.12.12. Others recommend doing other things. A Google through the debian-user, debian-laptop and acpi-support email lists will be of help to you if you're not sure what you should do for your specific system.
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-<version>/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.
If you would prefer to use a Debian-ized kernel instead of a fresh one, maxx has provided a pre-patched kernel-source package with the latest patch for the 2.4.20 kernel. This would be instead of downloading a fresh (non-patched) kernel from www.kernel.org. He sent me an email with the following details:
If you are already running a kernel that is the same version of the one you are about to patch I recommend creating a fresh directory for the newly patched kernel. Remember that backups are never a bad thing. These are the files that I back up:
Since I was starting on a brand new machine, I'm pretty sure I have the full list of required packages to make this whole patch go smoothly. Here's the list all in one go:
Download a fresh kernel from www.kernel.org. You need to make sure you get a full kernel. Find the "latest stable version of the Linux kernel" and click on F for FULL. Wait patiently. A bzipped kernel is about 26M. If you're feeling particularly geeky you could also wget http://kernel.org/pub/linux/kernel/v2.4/linux-<version>.tar.bz2.
While you're waiting, grab a copy of the patch as well. For the 2.4.20 kernel use the 2.4.20 patch. It's dated 2002.12.12. You'll need to know that number later when we check to make sure the patch worked. If you are using a different kernel version make sure you take note of the date of your patch. Your numbers will differ slightly from the one I use later on.
Once you've got those two files (the kernel and the patch) unpack them and patch the kernel.
First we're going to set the stage to patch the kernel. We need to unpack the bz2 file (bzip2) and shuffle the directories around a bit. /usr/src/linux probably points to your current kernel. We need it to point to the new kernel, so we'll do that as well.
Now we're going to actually patch the kernel. I take one extra step from the instructions at ACPI4Linux. Instead of gunzipping and patching in the same line, I use two lines. This is purely a matter of preference. When you patch the kernel you want to make sure there are no error messages. (There is no "yay" line, instead look for the absence of errors.)
Now instead of using make menuconfig, I have a godsend of an option. Check this out: copy your current .config file into /usr/src/linux. Now use "make oldconfig". It will run through your old config file and see what's been updated so that you don't have to find all the new options. For everything to do with ACPI (about the first 5 questions for me, but possibly more for you if you've never configured a pre-patched kernel) say M for module. There are an extra 3 or so things after that which I said "no" to.
In point form, this is how the kernel should be configured:
Now go in to the config file with make menuconfig. I want you do check and make sure you have your APM (the old stuff) turned off. Under ", make sure that: "
exit and save the new configuration
If you have additional modules that are not part of the main source tree, you will need to add modules_image when you make your Debian packages. This is almost inevitable if you're using a laptop. I have three things are not part of the stock kernel that I install separately: my graphics card (nvidia); sound (ALSA); and my wireless card (PCMCIA).
I like to configure lilo on my own, but do whatever tickles your fancy.
At this point you should reboot your machine. When your system comes back up (assuming of course that everything went well and you still have a system), check to see what kernel you're running with uname -a. It should show you the one you just built. You also need to make sure the correct patch was installed. You can do that with dmesg | grep ACPI.*Subsystem\ revision . It should give the output: ACPI: Subsystem revision 20021212. The revision is the date the patch was released. This number will be different than mine if you are not using the 2.4.20 kernel. To look at all ACPI-related bits that were loaded/started when your system rebooted, do this: dmesg | grep ACPI . dmesg prints your boot messages and grep ACPI makes sure that only ACPI-related messages are printed.
You can also check to see what version you're using with cat /proc/acpi/info. Don't believe everything you read though. My output says that S3 is a supported state, but we already know it's not. It does give the correct version though, which is useful.
If you compiled ACPI support in as "M"odules you'll probably need to load the modules by hand. You'll need to hunt around a bit to see what modules are there. Mine are in /lib/modules/<version>. <date>/kernel/drivers/acpi/, and are as follows:
The first time I rebooted I loaded them all by hand, typing insmod <modulename>. I personally load processor first, although there are mixed feelings on whether or not the order matters.
You can check to see which modules are loaded with lsmod. My output of lsmod (with most of the extras removed) looks like this:
The last one is my graphics card, which uses proprietary drivers. This is why I have a "P" next to Tainted on the top line.
To prevent having to load the modules each time you reboot you can do one of two things: compile them directly into the kernel (bit late for that though, eh?), or add them to your /etc/modules file. If you don't already have a copy of the file just create a new one and add each module name (remember, no dot-o) on a separate line.
Don't let apmd and acpid run at the same time unless you REALLY know what you're doing. Debian will not make sure only one is running at a time. You will have to check. APM will try to put your system into S3. On the 2.4.x (and before) series kernels this will quite probably hang your machine. S3 is not supported until 2.5.x. Even the patch won't provide support for S3. I personally did an apt-get remove apmd to solve the hanging problem.
You should also be aware of another little glitch I discovered. The XFree86 server has an option for DPMS (Energy Star) features. The DPMS can states can be one of standby, suspend, off or on. Since the 2.4.x kernels cannot suspend to disk, this can cause problems. I fixed my system by doing two things:
There are a few different applications/daemons you will want to install on your system: acpid (the daemon that will control your hardware states), and acpi (the interface to monitor events and states) are the base install. The acpi Debian package is only available in testing and is unstable. If you're running stable you won't be able to install it without playing around with apt and your list.sources file. You can probably also compile from source. If you do get acpi installed you can use it to monitor your system like this: acpi -V. The output will tell you about your system. Mine looks like this:
Unfortunately, the -V "full version" doesn't work for me. Fortunately I can still look in each of the acpi files individually for information about my system. Check in the /proc/acpi directory for various things of importance. If I want to check my battery I read the following file like this: cat /proc/acpi/battery/BAT0/state. The output is as follows:
If I want information about my battery in general I check it out like this: cat /proc/acpi/battery/BAT0/info
You're smart people. You can probably figure it out from here. :)
The following URLs were incredibly useful in writing this HOWTO and generally getting ACPI up and running.
Hardware-specific Install Reports and Info
Software Development Groups
Mailing List Threads
ACPI packages and related software
Much thanks goes out to the following:
There is very little difference between The Debian Way and the generic way. In fact it's probably only 10 or so lines of difference.
The "normal" way of compiling a kernel does not use make-kpkg. Instead, it uses the following steps:
In The Debian Way, you create a deb file which contains information about where the kernel is (and makes the kernel and yada-yada). In the "normal" way, you put things where they need to be right away. You need to install your modules and then configure lilo to point to the new kernel and then run lilo. If you are not doing things The Debian Way your "install" will look like this:
You can still use all of the software mentioned in this HOWTO even if you're not using Debian. Unfortunately it will take a little more effort on your part to download and install everything. Fortunately it's really not that difficult. Most software packages include a README file when you gunzip them which will explain what you need to do to get things working on your system.
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