ACPI @ Linux kernel

"Power", the big problem and issue in any electronic devices. How to save Power consumed is a good topic for us, in Hardware part, we would hear some Power technologies in usually, such as "Power Gating", "Power Management", "DVFS"... all of the targets is to turn off the unused hardware and keep the power consumed stability without charged or discharged usually , because each charged or discharged, it would waist some power to change it's status and dynamic power would get higher in this moment, so the template thermal would get higher, that would damaged our electronic devices. but in power saving view, when to turn off the devices and how to get the more efficient without thermal, power waist.. so in software part, it define the each power status, that means the power status had it's own job, like G1, Sleeping subdivides into the four states S1 through S4: S1: All processor caches are flushed, and the CPU(s) stop executing instructions. Power to the CPU(s) and RAM is maintained; devices that do not indicate they must remain on may be powered down. ... and we can use power status table and some predictions to determine the status paths and when to change..., it can be easily to handle and turn off unused devices efficiency. Refs: SmartReflex™ Power and Performance Management Tech... DVFS emulator peak power power management 4 Linux power monitor part2 power monitor part1 Advanced Configuration and Power Interface