The power() callout gets called whenever power management needs to be
activated.
This callout is specific to the CPU and target.
The general CPU power modes are as follows:
- Active or Running
- The system is actively running applications.
Some peripherals or devices may be idle or shut down.
- Idle
- The system isn't running applications; the CPU is halted.
Code is all or partially resident in memory.
- Standby
- The system isn't running applications; the CPU is halted.
Code isn't resident in memory.
- Shutdown
- Minimal or zero-power state.
CPU, memory, and devices are all powered off.
These definitions are a guideline only; you can define multiple subsets
for each state (e.g. Idle1, Idle2, etc.).
Furthermore, not all these CPU power modes may be required or even possible for
a specific board or CPU.