Busy-Idle State Transitions

The driver must keep the framework informed of device state transitions from idle to busy or busy to idle. Where these transitions happen is entirely device specific. The transitions from idle to busy and from busy to idle depend on the nature of the device and the abstraction represented by the specific component. For example, SCSI disk target drivers typically export a single component, which represents whether the SCSI target disk drive is spun up or not. It is marked busy whenever there is an outstanding request to the drive and idle when the last queued request finishes. Some components are created and never marked busy (components created by pm-components(9) are created in an idle state). For example, the keyboard and mouse are never marked busy but have their idle time reset each time a keystroke or mouse event is processed.

The following interfaces notify the power management framework of busy-idle state transitions.