mirror of
https://github.com/torvalds/linux.git
synced 2024-11-14 08:02:07 +00:00
6bc08ed023
Correct the meaning of PM_HIBERNATION_PREPARE in the docs. References: http://lkml.kernel.org/r/20130512162717.GA6305@pd.tnic Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
56 lines
2.8 KiB
Plaintext
56 lines
2.8 KiB
Plaintext
Suspend notifiers
|
|
(C) 2007-2011 Rafael J. Wysocki <rjw@sisk.pl>, GPL
|
|
|
|
There are some operations that subsystems or drivers may want to carry out
|
|
before hibernation/suspend or after restore/resume, but they require the system
|
|
to be fully functional, so the drivers' and subsystems' .suspend() and .resume()
|
|
or even .prepare() and .complete() callbacks are not suitable for this purpose.
|
|
For example, device drivers may want to upload firmware to their devices after
|
|
resume/restore, but they cannot do it by calling request_firmware() from their
|
|
.resume() or .complete() routines (user land processes are frozen at these
|
|
points). The solution may be to load the firmware into memory before processes
|
|
are frozen and upload it from there in the .resume() routine.
|
|
A suspend/hibernation notifier may be used for this purpose.
|
|
|
|
The subsystems or drivers having such needs can register suspend notifiers that
|
|
will be called upon the following events by the PM core:
|
|
|
|
PM_HIBERNATION_PREPARE The system is going to hibernate, tasks will be frozen
|
|
immediately. This is different from PM_SUSPEND_PREPARE
|
|
below because here we do additional work between notifiers
|
|
and drivers freezing.
|
|
|
|
PM_POST_HIBERNATION The system memory state has been restored from a
|
|
hibernation image or an error occurred during
|
|
hibernation. Device drivers' restore callbacks have
|
|
been executed and tasks have been thawed.
|
|
|
|
PM_RESTORE_PREPARE The system is going to restore a hibernation image.
|
|
If all goes well, the restored kernel will issue a
|
|
PM_POST_HIBERNATION notification.
|
|
|
|
PM_POST_RESTORE An error occurred during restore from hibernation.
|
|
Device drivers' restore callbacks have been executed
|
|
and tasks have been thawed.
|
|
|
|
PM_SUSPEND_PREPARE The system is preparing for suspend.
|
|
|
|
PM_POST_SUSPEND The system has just resumed or an error occurred during
|
|
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 .
|