Re: What does CONFIG_PM mean?

[Tim Bird <tim.bird@xxxxxxxxxxx>]

Bruce Yang wrote:
> Hi:
>   I am reading the source codes, and find many macros to control the
> config.
>   I want to know what CONFIG_PM mean, and also want to know how to know
> other the meaning of such configurations?
>   Thanks

Help for options is found in the kernel configuration
files (named "Kconfig" and sprinkled throughout the
kernel source tree.)  The "CONFIG_" prefix is not
used in the configuration file.

----------------
[linux-2.6.12.2]$ find . -name "Kconfig" | xargs grep "config PM"
./arch/parisc/Kconfig:config PM
./arch/mips/Kconfig:config PMC_YOSEMITE
./arch/mips/Kconfig:config PM
./arch/ia64/Kconfig:config PM
./arch/m68knommu/Kconfig:config PM
./kernel/power/Kconfig:config PM
./kernel/power/Kconfig:config PM_DEBUG
./kernel/power/Kconfig:config PM_STD_PARTITION
./drivers/macintosh/Kconfig:config PMAC_SMU
./drivers/macintosh/Kconfig:config PMAC_PBOOK
./drivers/macintosh/Kconfig:config PM
./drivers/macintosh/Kconfig:config PMAC_APM_EMU
./drivers/macintosh/Kconfig:config PMAC_BACKLIGHT
----------------

Assuming you are not using parisc, mips, ia64 or m68knommu,
you should look in kernel/power/Kconfig:

----------------
[linux-2.6.12.2]$ vi kernel/power/Kconfig  # search for "^config PM"
config PM
        bool "Power Management support"
        ---help---
          "Power Management" means that parts of your computer are shut
          off or put into a power conserving "sleep" mode if they are not
          being used.  There are two competing standards for doing this: APM
          and ACPI.  If you want to use either one, say Y here and then also
          to the requisite support below.

          Power Management is most important for battery powered laptop
          computers; if you have a laptop, check out the Linux Laptop home
          page on the WWW at <http://www.linux-on-laptops.com/> or
          Tuxmobil - Linux on Mobile Computers at <http://www.tuxmobil.org/>
          and the Battery Powered Linux mini-HOWTO, available from
          <http://www.tldp.org/docs.html#howto>.

          Note that, even if you say N here, Linux on the x86 architecture
          will issue the hlt instruction if nothing is to be done, thereby
          sending the processor to sleep and saving power.
---------------

 -- Tim

=============================
Tim Bird
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Electronics
=============================


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