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PM: introduce hibernation and suspend notifiers
Make it possible to register hibernation and suspend notifiers, so that subsystems can perform hibernation-related or suspend-related operations that should not be carried out by device drivers' .suspend() and .resume() routines. [akpm@linux-foundation.org: build fixes] [akpm@linux-foundation.org: cleanups] Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Pavel Machek <pavel@ucw.cz> Cc: Nigel Cunningham <nigel@nigel.suspend2.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Suspend notifiers | ||
(C) 2007 Rafael J. Wysocki <rjw@sisk.pl>, GPL | ||
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There are some operations that device drivers may want to carry out in their | ||
.suspend() routines, but shouldn't, because they can cause the hibernation or | ||
suspend to fail. For example, a driver may want to allocate a substantial amount | ||
of memory (like 50 MB) in .suspend(), but that shouldn't be done after the | ||
swsusp's memory shrinker has run. | ||
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Also, there may be some operations, that subsystems want to carry out before a | ||
hibernation/suspend or after a restore/resume, requiring the system to be fully | ||
functional, so the drivers' .suspend() and .resume() routines are not suitable | ||
for this purpose. For example, device drivers may want to upload firmware to | ||
their devices after a restore from a hibernation image, but they cannot do it by | ||
calling request_firmware() from their .resume() routines (user land processes | ||
are frozen at this point). The solution may be to load the firmware into | ||
memory before processes are frozen and upload it from there in the .resume() | ||
routine. Of course, a hibernation notifier may be used for this purpose. | ||
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The subsystems that have such needs can register suspend notifiers that will be | ||
called upon the following events by the suspend core: | ||
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PM_HIBERNATION_PREPARE The system is going to hibernate or suspend, tasks will | ||
be frozen immediately. | ||
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PM_POST_HIBERNATION The system memory state has been restored from a | ||
hibernation image or an error occured during the | ||
hibernation. Device drivers' .resume() callbacks have | ||
been executed and tasks have been thawed. | ||
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PM_SUSPEND_PREPARE The system is preparing for a suspend. | ||
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PM_POST_SUSPEND The system has just resumed or an error occured during | ||
the suspend. Device drivers' .resume() callbacks have | ||
been executed and tasks have been thawed. | ||
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It is generally assumed that whatever the notifiers do for | ||
PM_HIBERNATION_PREPARE, should be undone for PM_POST_HIBERNATION. Analogously, | ||
operations performed for PM_SUSPEND_PREPARE should be reversed for | ||
PM_POST_SUSPEND. Additionally, all of the notifiers are called for | ||
PM_POST_HIBERNATION if one of them fails for PM_HIBERNATION_PREPARE, and | ||
all of the notifiers are called for PM_POST_SUSPEND if one of them fails for | ||
PM_SUSPEND_PREPARE. | ||
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The hibernation and suspend notifiers are called with pm_mutex held. They are | ||
defined in the usual way, but their last argument is meaningless (it is always | ||
NULL). To register and/or unregister a suspend notifier use the functions | ||
register_pm_notifier() and unregister_pm_notifier(), respectively, defined in | ||
include/linux/suspend.h . If you don't need to unregister the notifier, you can | ||
also use the pm_notifier() macro defined in include/linux/suspend.h . |
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