1 .. SPDX-License-Identifier: GPL-2.0 2 .. include:: <isonum.txt> 3 4 ============================= 5 Suspend/Hibernation Notifiers 6 ============================= 7 8 :Copyright: |copy| 2016 Intel Corporation 9 10 :Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> 11 12 13 There are some operations that subsystems or drivers may want to carry out 14 before hibernation/suspend or after restore/resume, but they require the system 15 to be fully functional, so the drivers' and subsystems' ``->suspend()`` and 16 ``->resume()`` or even ``->prepare()`` and ``->complete()`` callbacks are not 17 suitable for this purpose. 18 19 For example, device drivers may want to upload firmware to their devices after 20 resume/restore, but they cannot do it by calling :c:func:`request_firmware()` 21 from their ``->resume()`` or ``->complete()`` callback routines (user land 22 processes are frozen at these points). The solution may be to load the firmware 23 into memory before processes are frozen and upload it from there in the 24 ``->resume()`` routine. A suspend/hibernation notifier may be used for that. 25 26 Subsystems or drivers having such needs can register suspend notifiers that 27 will be called upon the following events by the PM core: 28 29 ``PM_HIBERNATION_PREPARE`` 30 The system is going to hibernate, tasks will be frozen immediately. This 31 is different from ``PM_SUSPEND_PREPARE`` below, because in this case 32 additional work is done between the notifiers and the invocation of PM 33 callbacks for the "freeze" transition. 34 35 ``PM_POST_HIBERNATION`` 36 The system memory state has been restored from a hibernation image or an 37 error occurred during hibernation. Device restore callbacks have been 38 executed and tasks have been thawed. 39 40 ``PM_RESTORE_PREPARE`` 41 The system is going to restore a hibernation image. If all goes well, 42 the restored image kernel will issue a ``PM_POST_HIBERNATION`` 43 notification. 44 45 ``PM_POST_RESTORE`` 46 An error occurred during restore from hibernation. Device restore 47 callbacks have been executed and tasks have been thawed. 48 49 ``PM_SUSPEND_PREPARE`` 50 The system is preparing for suspend. 51 52 ``PM_POST_SUSPEND`` 53 The system has just resumed or an error occurred during suspend. Device 54 resume callbacks have been executed and tasks have been thawed. 55 56 It is generally assumed that whatever the notifiers do for 57 ``PM_HIBERNATION_PREPARE``, should be undone for ``PM_POST_HIBERNATION``. 58 Analogously, operations carried out for ``PM_SUSPEND_PREPARE`` should be 59 reversed for ``PM_POST_SUSPEND``. 60 61 Moreover, if one of the notifiers fails for the ``PM_HIBERNATION_PREPARE`` or 62 ``PM_SUSPEND_PREPARE`` event, the notifiers that have already succeeded for that 63 event will be called for ``PM_POST_HIBERNATION`` or ``PM_POST_SUSPEND``, 64 respectively. 65 66 The hibernation and suspend notifiers are called with :c:data:`pm_mutex` held. 67 They are defined in the usual way, but their last argument is meaningless (it is 68 always NULL). 69 70 To register and/or unregister a suspend notifier use 71 :c:func:`register_pm_notifier()` and :c:func:`unregister_pm_notifier()`, 72 respectively (both defined in :file:`include/linux/suspend.h`). If you don't 73 need to unregister the notifier, you can also use the :c:func:`pm_notifier()` 74 macro defined in :file:`include/linux/suspend.h`.
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.