path: root/Documentation/power/interface.txt
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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/power/interface.txt
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!
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+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'
+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
+/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