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Diffstat (limited to 'Documentation/power/notifiers.txt')
| -rw-r--r-- | Documentation/power/notifiers.txt | 51 |
1 files changed, 23 insertions, 28 deletions
diff --git a/Documentation/power/notifiers.txt b/Documentation/power/notifiers.txt index cf98070..c2a4a34 100644 --- a/Documentation/power/notifiers.txt +++ b/Documentation/power/notifiers.txt @@ -1,46 +1,41 @@ 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: + (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 or suspend, tasks will be frozen immediately. PM_POST_HIBERNATION The system memory state has been restored from a - hibernation image or an error occurred during the - hibernation. Device drivers' .resume() callbacks have + 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 + If all goes well, the restored kernel will issue a PM_POST_HIBERNATION notification. -PM_POST_RESTORE An error occurred during the hibernation restore. - Device drivers' .resume() callbacks have been executed +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 a suspend. +PM_SUSPEND_PREPARE The system is preparing for suspend. PM_POST_SUSPEND The system has just resumed or an error occurred during - the suspend. Device drivers' .resume() callbacks have - been executed and tasks have been thawed. + 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, |
