xref: /OK3568_Linux_fs/kernel/Documentation/power/apm-acpi.rst (revision 4882a59341e53eb6f0b4789bf948001014eff981)
1*4882a593Smuzhiyun============
2*4882a593SmuzhiyunAPM or ACPI?
3*4882a593Smuzhiyun============
4*4882a593Smuzhiyun
5*4882a593SmuzhiyunIf you have a relatively recent x86 mobile, desktop, or server system,
6*4882a593Smuzhiyunodds are it supports either Advanced Power Management (APM) or
7*4882a593SmuzhiyunAdvanced Configuration and Power Interface (ACPI).  ACPI is the newer
8*4882a593Smuzhiyunof the two technologies and puts power management in the hands of the
9*4882a593Smuzhiyunoperating system, allowing for more intelligent power management than
10*4882a593Smuzhiyunis possible with BIOS controlled APM.
11*4882a593Smuzhiyun
12*4882a593SmuzhiyunThe best way to determine which, if either, your system supports is to
13*4882a593Smuzhiyunbuild a kernel with both ACPI and APM enabled (as of 2.3.x ACPI is
14*4882a593Smuzhiyunenabled by default).  If a working ACPI implementation is found, the
15*4882a593SmuzhiyunACPI driver will override and disable APM, otherwise the APM driver
16*4882a593Smuzhiyunwill be used.
17*4882a593Smuzhiyun
18*4882a593SmuzhiyunNo, sorry, you cannot have both ACPI and APM enabled and running at
19*4882a593Smuzhiyunonce.  Some people with broken ACPI or broken APM implementations
20*4882a593Smuzhiyunwould like to use both to get a full set of working features, but you
21*4882a593Smuzhiyunsimply cannot mix and match the two.  Only one power management
22*4882a593Smuzhiyuninterface can be in control of the machine at once.  Think about it..
23*4882a593Smuzhiyun
24*4882a593SmuzhiyunUser-space Daemons
25*4882a593Smuzhiyun------------------
26*4882a593SmuzhiyunBoth APM and ACPI rely on user-space daemons, apmd and acpid
27*4882a593Smuzhiyunrespectively, to be completely functional.  Obtain both of these
28*4882a593Smuzhiyundaemons from your Linux distribution or from the Internet (see below)
29*4882a593Smuzhiyunand be sure that they are started sometime in the system boot process.
30*4882a593SmuzhiyunGo ahead and start both.  If ACPI or APM is not available on your
31*4882a593Smuzhiyunsystem the associated daemon will exit gracefully.
32*4882a593Smuzhiyun
33*4882a593Smuzhiyun  =====  =======================================
34*4882a593Smuzhiyun  apmd   http://ftp.debian.org/pool/main/a/apmd/
35*4882a593Smuzhiyun  acpid  http://acpid.sf.net/
36*4882a593Smuzhiyun  =====  =======================================
37