Separating Suspend and Hibernation
(Tue, 08 Apr 2008 17:39:25 +0000)
"The following three patches are intended to start the redesign of the suspend and hibernation framework for devices," began Rafael Wysocki. He noted that the first patch introduces new callbacks for suspend and hibernation, while the other two patches implement the new suspend and hibernation callbacks for the platform and PCI bus types. In describing the first patch in the series, he noted that previous callbacks were being phased out, explaining:
"The main purpose of doing this is to separate suspend (aka S2RAM and standby) callbacks from hibernation callbacks in such a way that the new callbacks won't take arguments and the semantics of each of them will be clearly specified. This has been requested for multiple times by many people, including Linus himself, and the reason is that within the current scheme if ->resume() is called, for example, it's difficult to say why it's been called (ie. is it a resume from RAM or from hibernation or a suspend/hibernation failure etc.?).
The second purpose is to make the suspend/hibernation callbacks more flexible so that device drivers can handle more than they can within the current scheme. For example, some drivers may need to prevent new children of the device from being registered before their ->suspend() callbacks are executed or they may want to carry out some operations requiring the availability of some other devices, not directly bound via the parent-child relationship, in order to prepare for the execution of ->suspend(), etc."