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diff --git a/Documentation/power/apm-acpi.rst b/Documentation/power/apm-acpi.rst new file mode 100644 index 000000000..5b90d9471 --- /dev/null +++ b/Documentation/power/apm-acpi.rst @@ -0,0 +1,36 @@ +============ +APM or ACPI? +============ + +If you have a relatively recent x86 mobile, desktop, or server system, +odds are it supports either Advanced Power Management (APM) or +Advanced Configuration and Power Interface (ACPI). ACPI is the newer +of the two technologies and puts power management in the hands of the +operating system, allowing for more intelligent power management than +is possible with BIOS controlled APM. + +The best way to determine which, if either, your system supports is to +build a kernel with both ACPI and APM enabled (as of 2.3.x ACPI is +enabled by default). If a working ACPI implementation is found, the +ACPI driver will override and disable APM, otherwise the APM driver +will be used. + +No, sorry, you cannot have both ACPI and APM enabled and running at +once. Some people with broken ACPI or broken APM implementations +would like to use both to get a full set of working features, but you +simply cannot mix and match the two. Only one power management +interface can be in control of the machine at once. Think about it.. + +User-space Daemons +------------------ +Both APM and ACPI rely on user-space daemons, apmd and acpid +respectively, to be completely functional. Obtain both of these +daemons from your Linux distribution or from the Internet (see below) +and be sure that they are started sometime in the system boot process. +Go ahead and start both. If ACPI or APM is not available on your +system the associated daemon will exit gracefully. + + ===== ======================================= + apmd http://ftp.debian.org/pool/main/a/apmd/ + acpid http://acpid.sf.net/ + ===== ======================================= |