Based on kernel version 2.6.26. Page generated on 2008-07-16 21:13 EST.
1 Suspend notifiers 2 (C) 2007 Rafael J. Wysocki <rjw[AT]sisk[DOT]pl>, GPL 3 4 There are some operations that device drivers may want to carry out in their 5 .suspend() routines, but shouldn't, because they can cause the hibernation or 6 suspend to fail. For example, a driver may want to allocate a substantial amount 7 of memory (like 50 MB) in .suspend(), but that shouldn't be done after the 8 swsusp's memory shrinker has run. 9 10 Also, there may be some operations, that subsystems want to carry out before a 11 hibernation/suspend or after a restore/resume, requiring the system to be fully 12 functional, so the drivers' .suspend() and .resume() routines are not suitable 13 for this purpose. For example, device drivers may want to upload firmware to 14 their devices after a restore from a hibernation image, but they cannot do it by 15 calling request_firmware() from their .resume() routines (user land processes 16 are frozen at this point). The solution may be to load the firmware into 17 memory before processes are frozen and upload it from there in the .resume() 18 routine. Of course, a hibernation notifier may be used for this purpose. 19 20 The subsystems that have such needs can register suspend notifiers that will be 21 called upon the following events by the suspend core: 22 23 PM_HIBERNATION_PREPARE The system is going to hibernate or suspend, tasks will 24 be frozen immediately. 25 26 PM_POST_HIBERNATION The system memory state has been restored from a 27 hibernation image or an error occured during the 28 hibernation. Device drivers' .resume() callbacks have 29 been executed and tasks have been thawed. 30 31 PM_RESTORE_PREPARE The system is going to restore a hibernation image. 32 If all goes well the restored kernel will issue a 33 PM_POST_HIBERNATION notification. 34 35 PM_POST_RESTORE An error occurred during the hibernation restore. 36 Device drivers' .resume() callbacks have been executed 37 and tasks have been thawed. 38 39 PM_SUSPEND_PREPARE The system is preparing for a suspend. 40 41 PM_POST_SUSPEND The system has just resumed or an error occured during 42 the suspend. Device drivers' .resume() callbacks have 43 been executed and tasks have been thawed. 44 45 It is generally assumed that whatever the notifiers do for 46 PM_HIBERNATION_PREPARE, should be undone for PM_POST_HIBERNATION. Analogously, 47 operations performed for PM_SUSPEND_PREPARE should be reversed for 48 PM_POST_SUSPEND. Additionally, all of the notifiers are called for 49 PM_POST_HIBERNATION if one of them fails for PM_HIBERNATION_PREPARE, and 50 all of the notifiers are called for PM_POST_SUSPEND if one of them fails for 51 PM_SUSPEND_PREPARE. 52 53 The hibernation and suspend notifiers are called with pm_mutex held. They are 54 defined in the usual way, but their last argument is meaningless (it is always 55 NULL). To register and/or unregister a suspend notifier use the functions 56 register_pm_notifier() and unregister_pm_notifier(), respectively, defined in 57 include/linux/suspend.h . If you don't need to unregister the notifier, you can 58 also use the pm_notifier() macro defined in include/linux/suspend.h .