Based on kernel version 4.9. Page generated on 2016-12-21 14:36 EST.
1 Suspend notifiers 2 (C) 2007-2011 Rafael J. Wysocki <email@example.com>, GPL 3 4 There are some operations that subsystems or drivers may want to carry out 5 before hibernation/suspend or after restore/resume, but they require the system 6 to be fully functional, so the drivers' and subsystems' .suspend() and .resume() 7 or even .prepare() and .complete() callbacks are not suitable for this purpose. 8 For example, device drivers may want to upload firmware to their devices after 9 resume/restore, but they cannot do it by calling request_firmware() from their 10 .resume() or .complete() routines (user land processes are frozen at these 11 points). The solution may be to load the firmware into memory before processes 12 are frozen and upload it from there in the .resume() routine. 13 A suspend/hibernation notifier may be used for this purpose. 14 15 The subsystems or drivers having such needs can register suspend notifiers that 16 will be called upon the following events by the PM core: 17 18 PM_HIBERNATION_PREPARE The system is going to hibernate, tasks will be frozen 19 immediately. This is different from PM_SUSPEND_PREPARE 20 below because here we do additional work between notifiers 21 and drivers freezing. 22 23 PM_POST_HIBERNATION The system memory state has been restored from a 24 hibernation image or an error occurred during 25 hibernation. Device drivers' restore callbacks have 26 been executed and tasks have been thawed. 27 28 PM_RESTORE_PREPARE The system is going to restore a hibernation image. 29 If all goes well, the restored kernel will issue a 30 PM_POST_HIBERNATION notification. 31 32 PM_POST_RESTORE An error occurred during restore from hibernation. 33 Device drivers' restore callbacks have been executed 34 and tasks have been thawed. 35 36 PM_SUSPEND_PREPARE The system is preparing for suspend. 37 38 PM_POST_SUSPEND The system has just resumed or an error occurred during 39 suspend. Device drivers' resume callbacks have been 40 executed and tasks have been thawed. 41 42 It is generally assumed that whatever the notifiers do for 43 PM_HIBERNATION_PREPARE, should be undone for PM_POST_HIBERNATION. Analogously, 44 operations performed for PM_SUSPEND_PREPARE should be reversed for 45 PM_POST_SUSPEND. Additionally, all of the notifiers are called for 46 PM_POST_HIBERNATION if one of them fails for PM_HIBERNATION_PREPARE, and 47 all of the notifiers are called for PM_POST_SUSPEND if one of them fails for 48 PM_SUSPEND_PREPARE. 49 50 The hibernation and suspend notifiers are called with pm_mutex held. They are 51 defined in the usual way, but their last argument is meaningless (it is always 52 NULL). To register and/or unregister a suspend notifier use the functions 53 register_pm_notifier() and unregister_pm_notifier(), respectively, defined in 54 include/linux/suspend.h . If you don't need to unregister the notifier, you can 55 also use the pm_notifier() macro defined in include/linux/suspend.h .