51 lines
2.7 KiB
Text
51 lines
2.7 KiB
Text
|
Suspend notifiers
|
||
|
|
(C) 2007 Rafael J. Wysocki <rjw@sisk.pl>, GPL
|
||
|
|
|
||
|
|
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.
|
||
|
|
|
||
|
|
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.
|
||
|
|
|
||
|
|
The subsystems that have such needs can register suspend notifiers that will be
|
||
|
|
called upon the following events by the suspend core:
|
||
|
|
|
||
|
|
PM_HIBERNATION_PREPARE The system is going to hibernate or suspend, tasks will
|
||
|
|
be frozen immediately.
|
||
|
|
|
||
|
|
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.
|
||
|
|
|
||
|
|
PM_SUSPEND_PREPARE The system is preparing for a suspend.
|
||
|
|
|
||
|
|
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.
|
||
|
|
|
||
|
|
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.
|
||
|
|
|
||
|
|
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 .
|