config PM bool "Power Management support" depends on !IA64_HP_SIM ---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 or Tuxmobil - Linux on Mobile Computers at and the Battery Powered Linux mini-HOWTO, available from . 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. config PM_LEGACY bool "Legacy Power Management API (DEPRECATED)" depends on PM default n ---help--- Support for pm_register() and friends. This old API is obsoleted by the driver model. If unsure, say N. config PM_DEBUG bool "Power Management Debug Support" depends on PM ---help--- This option enables verbose debugging support in the Power Management code. This is helpful when debugging and reporting various PM bugs, like suspend support. config DISABLE_CONSOLE_SUSPEND bool "Keep console(s) enabled during suspend/resume (DANGEROUS)" depends on PM && PM_DEBUG default n ---help--- This option turns off the console suspend mechanism that prevents debug messages from reaching the console during the suspend/resume operations. This may be helpful when debugging device drivers' suspend/resume routines, but may itself lead to problems, for example if netconsole is used. config PM_TRACE bool "Suspend/resume event tracing" depends on PM && PM_DEBUG && X86_32 && EXPERIMENTAL default n ---help--- This enables some cheesy code to save the last PM event point in the RTC across reboots, so that you can debug a machine that just hangs during suspend (or more commonly, during resume). To use this debugging feature you should attempt to suspend the machine, then reboot it, then run dmesg -s 1000000 | grep 'hash matches' CAUTION: this option will cause your machine's real-time clock to be set to an invalid time after a resume. config SOFTWARE_SUSPEND bool "Software Suspend (Hibernation)" depends on PM && SWAP && (((X86 || PPC64_SWSUSP) && (!SMP || SUSPEND_SMP)) || ((FRV || PPC32) && !SMP)) ---help--- Enable the suspend to disk (STD) functionality, which is usually called "hibernation" in user interfaces. STD checkpoints the system and powers it off; and restores that checkpoint on reboot. You can suspend your machine with 'echo disk > /sys/power/state'. Alternatively, you can use the additional userland tools available from . In principle it does not require ACPI or APM, although for example ACPI will be used for the final steps when it is available. One of the reasons to use software suspend is that the firmware hooks for suspend states like suspend-to-RAM (STR) often don't work very well with Linux. It creates an image which is saved in your active swap. Upon the next boot, pass the 'resume=/dev/swappartition' argument to the kernel to have it detect the saved image, restore memory state from it, and continue to run as before. If you do not want the previous state to be reloaded, then use the 'noresume' kernel command line argument. Note, however, that fsck will be run on your filesystems and you will need to run mkswap against the swap partition used for the suspend. It also works with swap files to a limited extent (for details see ). Right now you may boot without resuming and resume later but in the meantime you cannot use the swap partition(s)/file(s) involved in suspending. Also in this case you must not use the filesystems that were mounted before the suspend. In particular, you MUST NOT MOUNT any journaled filesystems mounted before the suspend or they will get corrupted in a nasty way. For more information take a look at . config PM_STD_PARTITION string "Default resume partition" depends on SOFTWARE_SUSPEND default "" ---help--- The default resume partition is the partition that the suspend- to-disk implementation will look for a suspended disk image. The partition specified here will be different for almost every user. It should be a valid swap partition (at least for now) that is turned on before suspending. The partition specified can be overridden by specifying: resume=/dev/ which will set the resume partition to the device specified. Note there is currently not a way to specify which device to save the suspended image to. It will simply pick the first available swap device. config SUSPEND_SMP bool depends on HOTPLUG_CPU && (X86 || PPC64) && PM default y config APM_EMULATION tristate "Advanced Power Management Emulation" depends on PM && SYS_SUPPORTS_APM_EMULATION help APM is a BIOS specification for saving power using several different techniques. This is mostly useful for battery powered laptops with APM compliant BIOSes. If you say Y here, the system time will be reset after a RESUME operation, the /proc/apm device will provide battery status information, and user-space programs will receive notification of APM "events" (e.g. battery status change). In order to use APM, you will need supporting software. For location and more information, read and the Battery Powered Linux mini-HOWTO, available from . This driver does not spin down disk drives (see the hdparm(8) manpage ("man 8 hdparm") for that), and it doesn't turn off VESA-compliant "green" monitors. Generally, if you don't have a battery in your machine, there isn't much point in using this driver and you should say N. If you get random kernel OOPSes or reboots that don't seem to be related to anything, try disabling/enabling this option (or disabling/enabling APM in your BIOS).