PM / sleep / docs: Convert PM notifiers document to reST

Move the document describing PM notifiers (used during system sleep
state transitions) to Documentation/driver-api/pm/, convert it to reST
and update it to use current terminology.  Also replace the remaining
references to the old version of it in .txt documents with references
to the new one.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/driver-api/pm/devices.rst

@@ -620,7 +620,7 @@ been thawed.  Generally speaking, the PM notifiers are suitable for performing
 actions that either require user space to be available, or at least won't
 interfere with user space.
 
-For details refer to :file:`Documentation/power/notifiers.txt`.
+For details refer to :doc:`notifiers`.
 
 
 Device Low-Power (suspend) States

Documentation/driver-api/pm/index.rst

@@ -5,6 +5,7 @@ Device Power Management
 .. toctree::
 
    devices
+   notifiers
    types
 
 .. only::  subproject and html

Documentation/driver-api/pm/notifiers.rst

@@ -0,0 +1,70 @@
+=============================
+Suspend/Hibernation Notifiers
+=============================
+
+::
+
+ Copyright (c) 2016 Intel Corp., Rafael J. Wysocki <rafael.j.wysocki@intel.com>
+
+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 :c:func:`request_firmware()`
+from their ``->resume()`` or ``->complete()`` callback 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 that.
+
+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 in this case
+	additional work is done between the notifiers and the invocation of PM
+	callbacks for the "freeze" transition.
+
+``PM_POST_HIBERNATION``
+	The system memory state has been restored from a hibernation image or an
+	error occurred during hibernation.  Device 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 image kernel will issue a ``PM_POST_HIBERNATION``
+	notification.
+
+``PM_POST_RESTORE``
+	An error occurred during restore from hibernation.  Device 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
+	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 carried out for ``PM_SUSPEND_PREPARE`` should be
+reversed for ``PM_POST_SUSPEND``.
+
+Moreover, if one of the notifiers fails for the ``PM_HIBERNATION_PREPARE`` or
+``PM_SUSPEND_PREPARE`` event, the notifiers that have already succeeded for that
+event will be called for ``PM_POST_HIBERNATION`` or ``PM_POST_SUSPEND``,
+respectively.
+
+The hibernation and suspend notifiers are called with :c:data:`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
+:c:func:`register_pm_notifier()` and :c:func:`unregister_pm_notifier()`,
+respectively (both defined in :file:`include/linux/suspend.h`).  If you don't
+need to unregister the notifier, you can also use the :c:func:`pm_notifier()`
+macro defined in :file:`include/linux/suspend.h`.

Documentation/power/00-INDEX

@@ -14,8 +14,6 @@ freezing-of-tasks.txt
 	- How processes and controlled during suspend
 interface.txt
 	- Power management user interface in /sys/power
-notifiers.txt
-	- Registering suspend notifiers in device drivers
 opp.txt
 	- Operating Performance Point library
 pci.txt

Documentation/power/freezing-of-tasks.txt

@@ -197,7 +197,8 @@ tasks, since it generally exists anyway.
 
 A driver must have all firmwares it may need in RAM before suspend() is called.
 If keeping them is not practical, for example due to their size, they must be
-requested early enough using the suspend notifier API described in notifiers.txt.
+requested early enough using the suspend notifier API described in
+Documentation/driver-api/pm/notifiers.rst.
 
 VI. Are there any precautions to be taken to prevent freezing failures?
 

Documentation/power/pci.txt

@@ -713,7 +713,7 @@ In addition to that the prepare() callback may carry out some operations
 preparing the device to be suspended, although it should not allocate memory
 (if additional memory is required to suspend the device, it has to be
 preallocated earlier, for example in a suspend/hibernate notifier as described
-in Documentation/power/notifiers.txt).
+in Documentation/driver-api/pm/notifiers.rst).
 
 3.1.2. suspend()