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author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/power/interface.txt | |
download | linux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.bz2 |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'Documentation/power/interface.txt')
-rw-r--r-- | Documentation/power/interface.txt | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt new file mode 100644 index 000000000000..f5ebda5f4276 --- /dev/null +++ b/Documentation/power/interface.txt @@ -0,0 +1,43 @@ +Power Management Interface + + +The power management subsystem provides a unified sysfs interface to +userspace, regardless of what architecture or platform one is +running. The interface exists in /sys/power/ directory (assuming sysfs +is mounted at /sys). + +/sys/power/state controls system power state. Reading from this file +returns what states are supported, which is hard-coded to 'standby' +(Power-On Suspend), 'mem' (Suspend-to-RAM), and 'disk' +(Suspend-to-Disk). + +Writing to this file one of those strings causes the system to +transition into that state. Please see the file +Documentation/power/states.txt for a description of each of those +states. + + +/sys/power/disk controls the operating mode of the suspend-to-disk +mechanism. Suspend-to-disk can be handled in several ways. The +greatest distinction is who writes memory to disk - the firmware or +the kernel. If the firmware does it, we assume that it also handles +suspending the system. + +If the kernel does it, then we have three options for putting the system +to sleep - using the platform driver (e.g. ACPI or other PM +registers), powering off the system or rebooting the system (for +testing). The system will support either 'firmware' or 'platform', and +that is known a priori. But, the user may choose 'shutdown' or +'reboot' as alternatives. + +Reading from this file will display what the mode is currently set +to. Writing to this file will accept one of + + 'firmware' + 'platform' + 'shutdown' + 'reboot' + +It will only change to 'firmware' or 'platform' if the system supports +it. + |