Linux-libre 4.5-gnu

4 files changed, 7 insertions, 1481 deletions

diff --git a/Documentation/power/pci.txt b/Documentation/power/pci.txt
index b0e911e0e..44558882a 100644
--- a/Documentation/power/pci.txt
+++ b/Documentation/power/pci.txt
@@ -999,7 +999,7 @@ from its probe routine to make runtime PM work for the device.
 
 It is important to remember that the driver's runtime_suspend() callback
 may be executed right after the usage counter has been decremented, because
-user space may already have cuased the pm_runtime_allow() helper function
+user space may already have caused the pm_runtime_allow() helper function
 unblocking the runtime PM of the device to run via sysfs, so the driver must
 be prepared to cope with that.
 
diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt
index 0784bc3a2..7328cf852 100644
--- a/Documentation/power/runtime_pm.txt
+++ b/Documentation/power/runtime_pm.txt
@@ -371,6 +371,12 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
     - increment the device's usage counter, run pm_runtime_resume(dev) and
       return its result
 
+  int pm_runtime_get_if_in_use(struct device *dev);
+    - return -EINVAL if 'power.disable_depth' is nonzero; otherwise, if the
+      runtime PM status is RPM_ACTIVE and the runtime PM usage counter is
+      nonzero, increment the counter and return 1; otherwise return 0 without
+      changing the counter
+
   void pm_runtime_put_noidle(struct device *dev);
     - decrement the device's usage counter
 
diff --git a/Documentation/power/tuxonice-internals.txt b/Documentation/power/tuxonice-internals.txt
deleted file mode 100644
index 0c6a2163a..000000000
--- a/Documentation/power/tuxonice-internals.txt
+++ /dev/null
@@ -1,532 +0,0 @@
-		   TuxOnIce 4.0 Internal Documentation.
-			Updated to 23 March 2015
-
-(Please note that incremental image support mentioned in this document is work
-in progress. This document may need updating prior to the actual release of
-4.0!)
-
-1.  Introduction.
-
-    TuxOnIce 4.0 is an addition to the Linux Kernel, designed to
-    allow the user to quickly shutdown and quickly boot a computer, without
-    needing to close documents or programs. It is equivalent to the
-    hibernate facility in some laptops. This implementation, however,
-    requires no special BIOS or hardware support.
-
-    The code in these files is based upon the original implementation
-    prepared by Gabor Kuti and additional work by Pavel Machek and a
-    host of others. This code has been substantially reworked by Nigel
-    Cunningham, again with the help and testing of many others, not the
-    least of whom are Bernard Blackham and Michael Frank. At its heart,
-    however, the operation is essentially the same as Gabor's version.
-
-2.  Overview of operation.
-
-    The basic sequence of operations is as follows:
-
-	a. Quiesce all other activity.
-	b. Ensure enough memory and storage space are available, and attempt
-	   to free memory/storage if necessary.
-	c. Allocate the required memory and storage space.
-	d. Write the image.
-	e. Power down.
-
-    There are a number of complicating factors which mean that things are
-    not as simple as the above would imply, however...
-
-    o The activity of each process must be stopped at a point where it will
-    not be holding locks necessary for saving the image, or unexpectedly
-    restart operations due to something like a timeout and thereby make
-    our image inconsistent.
-
-    o It is desirous that we sync outstanding I/O to disk before calculating
-    image statistics. This reduces corruption if one should suspend but
-    then not resume, and also makes later parts of the operation safer (see
-    below).
-
-    o We need to get as close as we can to an atomic copy of the data.
-    Inconsistencies in the image will result in inconsistent memory contents at
-    resume time, and thus in instability of the system and/or file system
-    corruption. This would appear to imply a maximum image size of one half of
-    the amount of RAM, but we have a solution... (again, below).
-
-    o In 2.6 and later, we choose to play nicely with the other suspend-to-disk
-    implementations.
-
-3.  Detailed description of internals.
-
-    a. Quiescing activity.
-
-    Safely quiescing the system is achieved using three separate but related
-    aspects.
-
-    First, we use the vanilla kerne's support for freezing processes. This code
-    is based on the observation that the vast majority of processes don't need
-    to run during suspend. They can be 'frozen'. The kernel therefore
-    implements a refrigerator routine, which processes enter and in which they
-    remain until the cycle is complete. Processes enter the refrigerator via
-    try_to_freeze() invocations at appropriate places.  A process cannot be
-    frozen in any old place. It must not be holding locks that will be needed
-    for writing the image or freezing other processes. For this reason,
-    userspace processes generally enter the refrigerator via the signal
-    handling code, and kernel threads at the place in their event loops where
-    they drop locks and yield to other processes or sleep. The task of freezing
-    processes is complicated by the fact that there can be interdependencies
-    between processes. Freezing process A before process B may mean that
-    process B cannot be frozen, because it stops at waiting for process A
-    rather than in the refrigerator. This issue is seen where userspace waits
-    on freezeable kernel threads or fuse filesystem threads. To address this
-    issue, we implement the following algorithm for quiescing activity:
-
-	- Freeze filesystems (including fuse - userspace programs starting
-		new requests are immediately frozen; programs already running
-		requests complete their work before being frozen in the next
-		step)
-	- Freeze userspace
-	- Thaw filesystems (this is safe now that userspace is frozen and no
-		fuse requests are outstanding).
-	- Invoke sys_sync (noop on fuse).
-	- Freeze filesystems
-	- Freeze kernel threads
-
-    If we need to free memory, we thaw kernel threads and filesystems, but not
-    userspace. We can then free caches without worrying about deadlocks due to
-    swap files being on frozen filesystems or such like.
-
-    b. Ensure enough memory & storage are available.
-
-    We have a number of constraints to meet in order to be able to successfully
-    suspend and resume.
-
-    First, the image will be written in two parts, described below. One of
-    these parts needs to have an atomic copy made, which of course implies a
-    maximum size of one half of the amount of system memory. The other part
-    ('pageset') is not atomically copied, and can therefore be as large or
-    small as desired.
-
-    Second, we have constraints on the amount of storage available. In these
-    calculations, we may also consider any compression that will be done. The
-    cryptoapi module allows the user to configure an expected compression ratio.
-
-    Third, the user can specify an arbitrary limit on the image size, in
-    megabytes. This limit is treated as a soft limit, so that we don't fail the
-    attempt to suspend if we cannot meet this constraint.
-
-    c. Allocate the required memory and storage space.
-
-    Having done the initial freeze, we determine whether the above constraints
-    are met, and seek to allocate the metadata for the image. If the constraints
-    are not met, or we fail to allocate the required space for the metadata, we
-    seek to free the amount of memory that we calculate is needed and try again.
-    We allow up to four iterations of this loop before aborting the cycle. If
-    we do fail, it should only be because of a bug in TuxOnIce's calculations
-    or the vanilla kernel code for freeing memory.
-
-    These steps are merged together in the prepare_image function, found in
-    prepare_image.c. The functions are merged because of the cyclical nature
-    of the problem of calculating how much memory and storage is needed. Since
-    the data structures containing the information about the image must
-    themselves take memory and use storage, the amount of memory and storage
-    required changes as we prepare the image. Since the changes are not large,
-    only one or two iterations will be required to achieve a solution.
-
-    The recursive nature of the algorithm is miminised by keeping user space
-    frozen while preparing the image, and by the fact that our records of which
-    pages are to be saved and which pageset they are saved in use bitmaps (so
-    that changes in number or fragmentation of the pages to be saved don't
-    feedback via changes in the amount of memory needed for metadata). The
-    recursiveness is thus limited to any extra slab pages allocated to store the
-    extents that record storage used, and the effects of seeking to free memory.
-
-    d. Write the image.
-
-    We previously mentioned the need to create an atomic copy of the data, and
-    the half-of-memory limitation that is implied in this. This limitation is
-    circumvented by dividing the memory to be saved into two parts, called
-    pagesets.
-
-    Pageset2 contains most of the page cache - the pages on the active and
-    inactive LRU lists that aren't needed or modified while TuxOnIce is
-    running, so they can be safely written without an atomic copy. They are
-    therefore saved first and reloaded last. While saving these pages,
-    TuxOnIce carefully ensures that the work of writing the pages doesn't make
-    the image inconsistent. With the support for Kernel (Video) Mode Setting
-    going into the kernel at the time of writing, we need to check for pages
-    on the LRU that are used by KMS, and exclude them from pageset2. They are
-    atomically copied as part of pageset 1.
-
-    Once pageset2 has been saved, we prepare to do the atomic copy of remaining
-    memory. As part of the preparation, we power down drivers, thereby providing
-    them with the opportunity to have their state recorded in the image. The
-    amount of memory allocated by drivers for this is usually negligible, but if
-    DRI is in use, video drivers may require significants amounts. Ideally we
-    would be able to query drivers while preparing the image as to the amount of
-    memory they will need. Unfortunately no such mechanism exists at the time of
-    writing. For this reason, TuxOnIce allows the user to set an
-    'extra_pages_allowance', which is used to seek to ensure sufficient memory
-    is available for drivers at this point. TuxOnIce also lets the user set this
-    value to 0. In this case, a test driver suspend is done while preparing the
-    image, and the difference (plus a margin) used instead. TuxOnIce will also
-    automatically restart the hibernation process (twice at most) if it finds
-    that the extra pages allowance is not sufficient. It will then use what was
-    actually needed (plus a margin, again). Failure to hibernate should thus
-    be an extremely rare occurence.
-
-    Having suspended the drivers, we save the CPU context before making an
-    atomic copy of pageset1, resuming the drivers and saving the atomic copy.
-    After saving the two pagesets, we just need to save our metadata before
-    powering down.
-
-    As we mentioned earlier, the contents of pageset2 pages aren't needed once
-    they've been saved. We therefore use them as the destination of our atomic
-    copy. In the unlikely event that pageset1 is larger, extra pages are
-    allocated while the image is being prepared. This is normally only a real
-    possibility when the system has just been booted and the page cache is
-    small.
-
-    This is where we need to be careful about syncing, however. Pageset2 will
-    probably contain filesystem meta data. If this is overwritten with pageset1
-    and then a sync occurs, the filesystem will be corrupted - at least until
-    resume time and another sync of the restored data. Since there is a
-    possibility that the user might not resume or (may it never be!) that
-    TuxOnIce might oops, we do our utmost to avoid syncing filesystems after
-    copying pageset1.
-
-    e. Incremental images
-
-    TuxOnIce 4.0 introduces a new incremental image mode which changes things a
-    little. When incremental images are enabled, we save a 'normal' image the
-    first time we hibernate. One resume however, we do not free the image or
-    the associated storage. Instead, it is retained until the next attempt at
-    hibernating and a mechanism is enabled which is used to track which pages
-    of memory are modified between the two cycles. The modified pages can then
-    be added to the existing image, rather than unmodified pages being saved
-    again unnecessarily.
-
-    Incremental image support is available in 64 bit Linux only, due to the
-    requirement for extra page flags.
-
-    This support is accomplished in the following way:
-
-    1) Tracking of pages.
-
-    The tracking of changed pages is accomplished using the page fault
-    mechanism. When we reach a point at which we want to start tracking
-    changes, most pages are marked read-only and also flagged as being
-    read-only because of this support. Since this cannot happen for every page
-    of RAM, some are marked as untracked and always treated as modified whn
-    preparing an incremental iamge. When a process attempts to modify a page
-    that is marked read-only in this way, a page fault occurs, with TuxOnIce
-    code marking the page writable and dirty before allowing the write to
-    continue. In this way, the effect of incremental images on performance is
-    minimised - a page only causes a fault once. Small modifications to the
-    page allocator further reduce the number of faults that occur - free pages
-    are not tracked; they are made writable and marked as dirty as part of
-    being allocated.
-
-    2) Saving the incremental image / atomicity.
-
-    The page fault mechanism is also used to improve the means by which
-    atomicity of the image is acheived. When it is time to do an atomic copy,
-    the flags for pages are reset, with the result being that it is no longer
-    necessary for us to do an atomic of pageset1. Instead, we normally write
-    the uncopied pages to disk. When an attempt is made to modify a page that
-    has not yet been saved, the page-fault mechanism makes a copy of the page
-    prior to allowing the write. This copy is then written to disk. Likewise,
-    on resume, if a process attempts to write to a page that has been read
-    while the rest of the image is still being loaded, a copy of that page is
-    made prior to the write being allowed. At the end of loading the image,
-    modified pages can thus be restored to their 'atomic copy' contents prior
-    to restarting normal operation. We also mark pages that are yet to be read
-    as invalid PFNs, so that we can capture as a bug any attempt by a
-    half-restored kernel to access a page that hasn't yet been reloaded.
-
-    f. Power down.
-
-    Powering down uses standard kernel routines. TuxOnIce supports powering down
-    using the ACPI S3, S4 and S5 methods or the kernel's non-ACPI power-off.
-    Supporting suspend to ram (S3) as a power off option might sound strange,
-    but it allows the user to quickly get their system up and running again if
-    the battery doesn't run out (we just need to re-read the overwritten pages)
-    and if the battery does run out (or the user removes power), they can still
-    resume.
-
-4.  Data Structures.
-
-    TuxOnIce uses three main structures to store its metadata and configuration
-    information:
-
-    a) Pageflags bitmaps.
-
-    TuxOnIce records which pages will be in pageset1, pageset2, the destination
-    of the atomic copy and the source of the atomically restored image using
-    bitmaps. The code used is that written for swsusp, with small improvements
-    to match TuxOnIce's requirements.
-
-    The pageset1 bitmap is thus easily stored in the image header for use at
-    resume time.
-
-    As mentioned above, using bitmaps also means that the amount of memory and
-    storage required for recording the above information is constant. This
-    greatly simplifies the work of preparing the image. In earlier versions of
-    TuxOnIce, extents were used to record which pages would be stored. In that
-    case, however, eating memory could result in greater fragmentation of the
-    lists of pages, which in turn required more memory to store the extents and
-    more storage in the image header. These could in turn require further
-    freeing of memory, and another iteration. All of this complexity is removed
-    by having bitmaps.
-
-    Bitmaps also make a lot of sense because TuxOnIce only ever iterates
-    through the lists. There is therefore no cost to not being able to find the
-    nth page in order 0 time. We only need to worry about the cost of finding
-    the n+1th page, given the location of the nth page. Bitwise optimisations
-    help here.
-
-    b) Extents for block data.
-
-    TuxOnIce supports writing the image to multiple block devices. In the case
-    of swap, multiple partitions and/or files may be in use, and we happily use
-    them all (with the exception of compcache pages, which we allocate but do
-    not use). This use of multiple block devices is accomplished as follows:
-
-    Whatever the actual source of the allocated storage, the destination of the
-    image can be viewed in terms of one or more block devices, and on each
-    device, a list of sectors. To simplify matters, we only use contiguous,
-    PAGE_SIZE aligned sectors, like the swap code does.
-
-    Since sector numbers on each bdev may well not start at 0, it makes much
-    more sense to use extents here. Contiguous ranges of pages can thus be
-    represented in the extents by contiguous values.
-
-    Variations in block size are taken account of in transforming this data
-    into the parameters for bio submission.
-
-    We can thus implement a layer of abstraction wherein the core of TuxOnIce
-    doesn't have to worry about which device we're currently writing to or
-    where in the device we are. It simply requests that the next page in the
-    pageset or header be written, leaving the details to this lower layer.
-    The lower layer remembers where in the sequence of devices and blocks each
-    pageset starts. The header always starts at the beginning of the allocated
-    storage.
-
-    So extents are:
-
-    struct extent {
-      unsigned long minimum, maximum;
-      struct extent *next;
-    }
-
-    These are combined into chains of extents for a device:
-
-    struct extent_chain {
-      int size; /* size of the extent ie sum (max-min+1) */
-      int allocs, frees;
-      char *name;
-      struct extent *first, *last_touched;
-    };
-
-    For each bdev, we need to store a little more info (simplified definition):
-
-    struct toi_bdev_info {
-       struct block_device *bdev;
-
-       char uuid[17];
-       dev_t dev_t;
-       int bmap_shift;
-       int blocks_per_page;
-    };
-
-    The uuid is the main means used to identify the device in the storage
-    image. This means we can cope with the dev_t representation of a device
-    changing between saving the image and restoring it, as may happen on some
-    bioses or in the LVM case.
-
-    bmap_shift and blocks_per_page apply the effects of variations in blocks
-    per page settings for the filesystem and underlying bdev. For most
-    filesystems, these are the same, but for xfs, they can have independant
-    values.
-
-    Combining these two structures together, we have everything we need to
-    record what devices and what blocks on each device are being used to
-    store the image, and to submit i/o using bio_submit.
-
-    The last elements in the picture are a means of recording how the storage
-    is being used.
-
-    We do this first and foremost by implementing a layer of abstraction on
-    top of the devices and extent chains which allows us to view however many
-    devices there might be as one long storage tape, with a single 'head' that
-    tracks a 'current position' on the tape:
-
-    struct extent_iterate_state {
-      struct extent_chain *chains;
-      int num_chains;
-      int current_chain;
-      struct extent *current_extent;
-      unsigned long current_offset;
-    };
-
-    That is, *chains points to an array of size num_chains of extent chains.
-    For the filewriter, this is always a single chain. For the swapwriter, the
-    array is of size MAX_SWAPFILES.
-
-    current_chain, current_extent and current_offset thus point to the current
-    index in the chains array (and into a matching array of struct
-    suspend_bdev_info), the current extent in that chain (to optimise access),
-    and the current value in the offset.
-
-    The image is divided into three parts:
-    - The header
-    - Pageset 1
-    - Pageset 2
-
-    The header always starts at the first device and first block. We know its
-    size before we begin to save the image because we carefully account for
-    everything that will be stored in it.
-
-    The second pageset (LRU) is stored first. It begins on the next page after
-    the end of the header.
-
-    The first pageset is stored second. It's start location is only known once
-    pageset2 has been saved, since pageset2 may be compressed as it is written.
-    This location is thus recorded at the end of saving pageset2. It is page
-    aligned also.
-
-    Since this information is needed at resume time, and the location of extents
-    in memory will differ at resume time, this needs to be stored in a portable
-    way:
-
-    struct extent_iterate_saved_state {
-        int chain_num;
-        int extent_num;
-        unsigned long offset;
-    };
-
-    We can thus implement a layer of abstraction wherein the core of TuxOnIce
-    doesn't have to worry about which device we're currently writing to or
-    where in the device we are. It simply requests that the next page in the
-    pageset or header be written, leaving the details to this layer, and
-    invokes the routines to remember and restore the position, without having
-    to worry about the details of how the data is arranged on disk or such like.
-
-    c) Modules
-
-    One aim in designing TuxOnIce was to make it flexible. We wanted to allow
-    for the implementation of different methods of transforming a page to be
-    written to disk and different methods of getting the pages stored.
-
-    In early versions (the betas and perhaps Suspend1), compression support was
-    inlined in the image writing code, and the data structures and code for
-    managing swap were intertwined with the rest of the code. A number of people
-    had expressed interest in implementing image encryption, and alternative
-    methods of storing the image.
-
-    In order to achieve this, TuxOnIce was given a modular design.
-
-    A module is a single file which encapsulates the functionality needed
-    to transform a pageset of data (encryption or compression, for example),
-    or to write the pageset to a device. The former type of module is called
-    a 'page-transformer', the later a 'writer'.
-
-    Modules are linked together in pipeline fashion. There may be zero or more
-    page transformers in a pipeline, and there is always exactly one writer.
-    The pipeline follows this pattern:
-
-		---------------------------------
-		|          TuxOnIce Core        |
-		---------------------------------
-				|
-				|
-		---------------------------------
-		|	Page transformer 1	|
-		---------------------------------
-				|
-				|
-		---------------------------------
-		|	Page transformer 2	|
-		---------------------------------
-				|
-				|
-		---------------------------------
-		|            Writer		|
-		---------------------------------
-
-    During the writing of an image, the core code feeds pages one at a time
-    to the first module. This module performs whatever transformations it
-    implements on the incoming data, completely consuming the incoming data and
-    feeding output in a similar manner to the next module.
-
-    All routines are SMP safe, and the final result of the transformations is
-    written with an index (provided by the core) and size of the output by the
-    writer. As a result, we can have multithreaded I/O without needing to
-    worry about the sequence in which pages are written (or read).
-
-    During reading, the pipeline works in the reverse direction. The core code
-    calls the first module with the address of a buffer which should be filled.
-    (Note that the buffer size is always PAGE_SIZE at this time). This module
-    will in turn request data from the next module and so on down until the
-    writer is made to read from the stored image.
-
-    Part of definition of the structure of a module thus looks like this:
-
-        int (*rw_init) (int rw, int stream_number);
-        int (*rw_cleanup) (int rw);
-        int (*write_chunk) (struct page *buffer_page);
-        int (*read_chunk) (struct page *buffer_page, int sync);
-
-    It should be noted that the _cleanup routine may be called before the
-    full stream of data has been read or written. While writing the image,
-    the user may (depending upon settings) choose to abort suspending, and
-    if we are in the midst of writing the last portion of the image, a portion
-    of the second pageset may be reread. This may also happen if an error
-    occurs and we seek to abort the process of writing the image.
-
-    The modular design is also useful in a number of other ways. It provides
-    a means where by we can add support for:
-
-    - providing overall initialisation and cleanup routines;
-    - serialising configuration information in the image header;
-    - providing debugging information to the user;
-    - determining memory and image storage requirements;
-    - dis/enabling components at run-time;
-    - configuring the module (see below);
-
-    ...and routines for writers specific to their work:
-    - Parsing a resume= location;
-    - Determining whether an image exists;
-    - Marking a resume as having been attempted;
-    - Invalidating an image;
-
-    Since some parts of the core - the user interface and storage manager
-    support - have use for some of these functions, they are registered as
-    'miscellaneous' modules as well.
-
-    d) Sysfs data structures.
-
-    This brings us naturally to support for configuring TuxOnIce. We desired to
-    provide a way to make TuxOnIce as flexible and configurable as possible.
-    The user shouldn't have to reboot just because they want to now hibernate to
-    a file instead of a partition, for example.
-
-    To accomplish this, TuxOnIce implements a very generic means whereby the
-    core and modules can register new sysfs entries. All TuxOnIce entries use
-    a single _store and _show routine, both of which are found in
-    tuxonice_sysfs.c in the kernel/power directory. These routines handle the
-    most common operations - getting and setting the values of bits, integers,
-    longs, unsigned longs and strings in one place, and allow overrides for
-    customised get and set options as well as side-effect routines for all
-    reads and writes.
-
-    When combined with some simple macros, a new sysfs entry can then be defined
-    in just a couple of lines:
-
-        SYSFS_INT("progress_granularity", SYSFS_RW, &progress_granularity, 1,
-                        2048, 0, NULL),
-
-    This defines a sysfs entry named "progress_granularity" which is rw and
-    allows the user to access an integer stored at &progress_granularity, giving
-    it a value between 1 and 2048 inclusive.
-
-    Sysfs entries are registered under /sys/power/tuxonice, and entries for
-    modules are located in a subdirectory named after the module.
-
diff --git a/Documentation/power/tuxonice.txt b/Documentation/power/tuxonice.txt
deleted file mode 100644
index 3bf0575ef..000000000
--- a/Documentation/power/tuxonice.txt
+++ /dev/null
@@ -1,948 +0,0 @@
-	--- TuxOnIce, version 3.0 ---
-
-1.  What is it?
-2.  Why would you want it?
-3.  What do you need to use it?
-4.  Why not just use the version already in the kernel?
-5.  How do you use it?
-6.  What do all those entries in /sys/power/tuxonice do?
-7.  How do you get support?
-8.  I think I've found a bug. What should I do?
-9.  When will XXX be supported?
-10  How does it work?
-11. Who wrote TuxOnIce?
-
-1. What is it?
-
-   Imagine you're sitting at your computer, working away. For some reason, you
-   need to turn off your computer for a while - perhaps it's time to go home
-   for the day. When you come back to your computer next, you're going to want
-   to carry on where you left off. Now imagine that you could push a button and
-   have your computer store the contents of its memory to disk and power down.
-   Then, when you next start up your computer, it loads that image back into
-   memory and you can carry on from where you were, just as if you'd never
-   turned the computer off. You have far less time to start up, no reopening of
-   applications or finding what directory you put that file in yesterday.
-   That's what TuxOnIce does.
-
-   TuxOnIce has a long heritage. It began life as work by Gabor Kuti, who,
-   with some help from Pavel Machek, got an early version going in 1999. The
-   project was then taken over by Florent Chabaud while still in alpha version
-   numbers. Nigel Cunningham came on the scene when Florent was unable to
-   continue, moving the project into betas, then 1.0, 2.0 and so on up to
-   the present series. During the 2.0 series, the name was contracted to
-   Suspend2 and the website suspend2.net created. Beginning around July 2007,
-   a transition to calling the software TuxOnIce was made, to seek to help
-   make it clear that TuxOnIce is more concerned with hibernation than suspend
-   to ram.
-
-   Pavel Machek's swsusp code, which was merged around 2.5.17 retains the
-   original name, and was essentially a fork of the beta code until Rafael
-   Wysocki came on the scene in 2005 and began to improve it further.
-
-2. Why would you want it?
-
-   Why wouldn't you want it?
-
-   Being able to save the state of your system and quickly restore it improves
-   your productivity - you get a useful system in far less time than through
-   the normal boot process. You also get to be completely 'green', using zero
-   power, or as close to that as possible (the computer may still provide
-   minimal power to some devices, so they can initiate a power on, but that
-   will be the same amount of power as would be used if you told the computer
-   to shutdown.
-
-3. What do you need to use it?
-
-   a. Kernel Support.
-
-   i) The TuxOnIce patch.
-
-   TuxOnIce is part of the Linux Kernel. This version is not part of Linus's
-   2.6 tree at the moment, so you will need to download the kernel source and
-   apply the latest patch. Having done that, enable the appropriate options in
-   make [menu|x]config (under Power Management Options - look for "Enhanced
-   Hibernation"), compile and install your kernel. TuxOnIce works with SMP,
-   Highmem, preemption, fuse filesystems, x86-32, PPC and x86_64.
-
-   TuxOnIce patches are available from http://tuxonice.net.
-
-   ii) Compression support.
-
-   Compression support is implemented via the cryptoapi. You will therefore want
-   to select any Cryptoapi transforms that you want to use on your image from
-   the Cryptoapi menu while configuring your kernel. We recommend the use of the
-   LZO compression method - it is very fast and still achieves good compression.
-
-   You can also tell TuxOnIce to write its image to an encrypted and/or
-   compressed filesystem/swap partition. In that case, you don't need to do
-   anything special for TuxOnIce when it comes to kernel configuration.
-
-   iii) Configuring other options.
-
-   While you're configuring your kernel, try to configure as much as possible
-   to build as modules. We recommend this because there are a number of drivers
-   that are still in the process of implementing proper power management
-   support. In those cases, the best way to work around their current lack is
-   to build them as modules and remove the modules while hibernating. You might
-   also bug the driver authors to get their support up to speed, or even help!
-
-   b. Storage.
-
-   i) Swap.
-
-   TuxOnIce can store the hibernation image in your swap partition, a swap file or
-   a combination thereof. Whichever combination you choose, you will probably
-   want to create enough swap space to store the largest image you could have,
-   plus the space you'd normally use for swap. A good rule of thumb would be
-   to calculate the amount of swap you'd want without using TuxOnIce, and then
-   add the amount of memory you have. This swapspace can be arranged in any way
-   you'd like. It can be in one partition or file, or spread over a number. The
-   only requirement is that they be active when you start a hibernation cycle.
-
-   There is one exception to this requirement. TuxOnIce has the ability to turn
-   on one swap file or partition at the start of hibernating and turn it back off
-   at the end. If you want to ensure you have enough memory to store a image
-   when your memory is fully used, you might want to make one swap partition or
-   file for 'normal' use, and another for TuxOnIce to activate & deactivate
-   automatically. (Further details below).
-
-   ii) Normal files.
-
-   TuxOnIce includes a 'file allocator'. The file allocator can store your
-   image in a simple file. Since Linux has the concept of everything being a
-   file, this is more powerful than it initially sounds. If, for example, you
-   were to set up a network block device file, you could hibernate to a network
-   server. This has been tested and works to a point, but nbd itself isn't
-   stateless enough for our purposes.
-
-   Take extra care when setting up the file allocator. If you just type
-   commands without thinking and then try to hibernate, you could cause
-   irreversible corruption on your filesystems! Make sure you have backups.
-
-   Most people will only want to hibernate to a local file. To achieve that, do
-   something along the lines of:
-
-   echo "TuxOnIce" > /hibernation-file
-   dd if=/dev/zero bs=1M count=512 >> /hibernation-file
-
-   This will create a 512MB file called /hibernation-file. To get TuxOnIce to use
-   it:
-
-   echo /hibernation-file > /sys/power/tuxonice/file/target
-
-   Then
-
-   cat /sys/power/tuxonice/resume
-
-   Put the results of this into your bootloader's configuration (see also step
-   C, below):
-
-   ---EXAMPLE-ONLY-DON'T-COPY-AND-PASTE---
-   # cat /sys/power/tuxonice/resume
-   file:/dev/hda2:0x1e001
-
-   In this example, we would edit the append= line of our lilo.conf|menu.lst
-   so that it included:
-
-   resume=file:/dev/hda2:0x1e001
-   ---EXAMPLE-ONLY-DON'T-COPY-AND-PASTE---
-
-   For those who are thinking 'Could I make the file sparse?', the answer is
-   'No!'. At the moment, there is no way for TuxOnIce to fill in the holes in
-   a sparse file while hibernating. In the longer term (post merge!), I'd like
-   to change things so that the file could be dynamically resized and have
-   holes filled as needed. Right now, however, that's not possible and not a
-   priority.
-
-   c. Bootloader configuration.
-
-   Using TuxOnIce also requires that you add an extra parameter to
-   your lilo.conf or equivalent. Here's an example for a swap partition:
-
-   append="resume=swap:/dev/hda1"
-
-   This would tell TuxOnIce that /dev/hda1 is a swap partition you
-   have. TuxOnIce will use the swap signature of this partition as a
-   pointer to your data when you hibernate. This means that (in this example)
-   /dev/hda1 doesn't need to be _the_ swap partition where all of your data
-   is actually stored. It just needs to be a swap partition that has a
-   valid signature.
-
-   You don't need to have a swap partition for this purpose. TuxOnIce
-   can also use a swap file, but usage is a little more complex. Having made
-   your swap file, turn it on and do
-
-   cat /sys/power/tuxonice/swap/headerlocations
-
-   (this assumes you've already compiled your kernel with TuxOnIce
-   support and booted it). The results of the cat command will tell you
-   what you need to put in lilo.conf:
-
-   For swap partitions like /dev/hda1, simply use resume=/dev/hda1.
-   For swapfile `swapfile`, use resume=swap:/dev/hda2:0x242d.
-
-   If the swapfile changes for any reason (it is moved to a different
-   location, it is deleted and recreated, or the filesystem is
-   defragmented) then you will have to check
-   /sys/power/tuxonice/swap/headerlocations for a new resume_block value.
-
-   Once you've compiled and installed the kernel and adjusted your bootloader
-   configuration, you should only need to reboot for the most basic part
-   of TuxOnIce to be ready.
-
-   If you only compile in the swap allocator, or only compile in the file
-   allocator, you don't need to add the "swap:" part of the resume=
-   parameters above. resume=/dev/hda2:0x242d will work just as well. If you
-   have compiled both and your storage is on swap, you can also use this
-   format (the swap allocator is the default allocator).
-
-   When compiling your kernel, one of the options in the 'Power Management
-   Support' menu, just above the 'Enhanced Hibernation (TuxOnIce)' entry is
-   called 'Default resume partition'. This can be used to set a default value
-   for the resume= parameter.
-
-   d. The hibernate script.
-
-   Since the driver model in 2.6 kernels is still being developed, you may need
-   to do more than just configure TuxOnIce. Users of TuxOnIce usually start the
-   process via a script which prepares for the hibernation cycle, tells the
-   kernel to do its stuff and then restore things afterwards. This script might
-   involve:
-
-   - Switching to a text console and back if X doesn't like the video card
-     status on resume.
-   - Un/reloading drivers that don't play well with hibernation.
-
-   Note that you might not be able to unload some drivers if there are
-   processes using them. You might have to kill off processes that hold
-   devices open. Hint: if your X server accesses an USB mouse, doing a
-   'chvt' to a text console releases the device and you can unload the
-   module.
-
-   Check out the latest script (available on tuxonice.net).
-
-   e. The userspace user interface.
-
-   TuxOnIce has very limited support for displaying status if you only apply
-   the kernel patch - it can printk messages, but that is all. In addition,
-   some of the functions mentioned in this document (such as cancelling a cycle
-   or performing interactive debugging) are unavailable. To utilise these
-   functions, or simply get a nice display, you need the 'userui' component.
-   Userui comes in three flavours, usplash, fbsplash and text. Text should
-   work on any console. Usplash and fbsplash require the appropriate
-   (distro specific?) support.
-
-   To utilise a userui, TuxOnIce just needs to be told where to find the
-   userspace binary:
-
-   echo "/usr/local/sbin/tuxoniceui_fbsplash" > /sys/power/tuxonice/user_interface/program
-
-   The hibernate script can do this for you, and a default value for this
-   setting can be configured when compiling the kernel. This path is also
-   stored in the image header, so if you have an initrd or initramfs, you can
-   use the userui during the first part of resuming (prior to the atomic
-   restore) by putting the binary in the same path in your initrd/ramfs.
-   Alternatively, you can put it in a different location and do an echo
-   similar to the above prior to the echo > do_resume. The value saved in the
-   image header will then be ignored.
-
-4. Why not just use the version already in the kernel?
-
-   The version in the vanilla kernel has a number of drawbacks. The most
-   serious of these are:
-	- it has a maximum image size of 1/2 total memory;
-	- it doesn't allocate storage until after it has snapshotted memory.
-	  This means that you can't be sure hibernating will work until you
-	  see it start to write the image;
-	- it does not allow you to press escape to cancel a cycle;
-	- it does not allow you to press escape to cancel resuming;
-	- it does not allow you to automatically swapon a file when
-	  starting a cycle;
-	- it does not allow you to use multiple swap partitions or files;
-	- it does not allow you to use ordinary files;
-	- it just invalidates an image and continues to boot if you
-	  accidentally boot the wrong kernel after hibernating;
-	- it doesn't support any sort of nice display while hibernating;
-	- it is moving toward requiring that you have an initrd/initramfs
-	  to ever have a hope of resuming (uswsusp). While uswsusp will
-	  address some of the concerns above, it won't address all of them,
-          and will be more complicated to get set up;
-        - it doesn't have support for suspend-to-both (write a hibernation
-	  image, then suspend to ram; I think this is known as ReadySafe
-	  under M$).
-
-5. How do you use it?
-
-   A hibernation cycle can be started directly by doing:
-
-	echo > /sys/power/tuxonice/do_hibernate
-
-   In practice, though, you'll probably want to use the hibernate script
-   to unload modules, configure the kernel the way you like it and so on.
-   In that case, you'd do (as root):
-
-	hibernate
-
-   See the hibernate script's man page for more details on the options it
-   takes.
-
-   If you're using the text or splash user interface modules, one feature of
-   TuxOnIce that you might find useful is that you can press Escape at any time
-   during hibernating, and the process will be aborted.
-
-   Due to the way hibernation works, this means you'll have your system back and
-   perfectly usable almost instantly. The only exception is when it's at the
-   very end of writing the image. Then it will need to reload a small (usually
-   4-50MBs, depending upon the image characteristics) portion first.
-
-   Likewise, when resuming, you can press escape and resuming will be aborted.
-   The computer will then powerdown again according to settings at that time for
-   the powerdown method or rebooting.
-
-   You can change the settings for powering down while the image is being
-   written by pressing 'R' to toggle rebooting and 'O' to toggle between
-   suspending to ram and powering down completely).
-
-   If you run into problems with resuming, adding the "noresume" option to
-   the kernel command line will let you skip the resume step and recover your
-   system. This option shouldn't normally be needed, because TuxOnIce modifies
-   the image header prior to the atomic restore, and will thus prompt you
-   if it detects that you've tried to resume an image before (this flag is
-   removed if you press Escape to cancel a resume, so you won't be prompted
-   then).
-
-   Recent kernels (2.6.24 onwards) add support for resuming from a different
-   kernel to the one that was hibernated (thanks to Rafael for his work on
-   this - I've just embraced and enhanced the support for TuxOnIce). This
-   should further reduce the need for you to use the noresume option.
-
-6. What do all those entries in /sys/power/tuxonice do?
-
-   /sys/power/tuxonice is the directory which contains files you can use to
-   tune and configure TuxOnIce to your liking. The exact contents of
-   the directory will depend upon the version of TuxOnIce you're
-   running and the options you selected at compile time. In the following
-   descriptions, names in brackets refer to compile time options.
-   (Note that they're all dependant upon you having selected CONFIG_TUXONICE
-   in the first place!).
-
-   Since the values of these settings can open potential security risks, the
-   writeable ones are accessible only to the root user. You may want to
-   configure sudo to allow you to invoke your hibernate script as an ordinary
-   user.
-
-   - alloc/failure_test
-
-   This debugging option provides a way of testing TuxOnIce's handling of
-   memory allocation failures. Each allocation type that TuxOnIce makes has
-   been given a unique number (see the source code). Echo the appropriate
-   number into this entry, and when TuxOnIce attempts to do that allocation,
-   it will pretend there was a failure and act accordingly.
-
-   - alloc/find_max_mem_allocated
-
-   This debugging option will cause TuxOnIce to find the maximum amount of
-   memory it used during a cycle, and report that information in debugging
-   information at the end of the cycle.
-
-   - alt_resume_param
-
-   Instead of powering down after writing a hibernation image, TuxOnIce
-   supports resuming from a different image. This entry lets you set the
-   location of the signature for that image (the resume= value you'd use
-   for it). Using an alternate image and keep_image mode, you can do things
-   like using an alternate image to power down an uninterruptible power
-   supply.
-
-   - block_io/target_outstanding_io
-
-   This value controls the amount of memory that the block I/O code says it
-   needs when the core code is calculating how much memory is needed for
-   hibernating and for resuming. It doesn't directly control the amount of
-   I/O that is submitted at any one time - that depends on the amount of
-   available memory (we may have more available than we asked for), the
-   throughput that is being achieved and the ability of the CPU to keep up
-   with disk throughput (particularly where we're compressing pages).
-
-   - checksum/enabled
-
-   Use cryptoapi hashing routines to verify that Pageset2 pages don't change
-   while we're saving the first part of the image, and to get any pages that
-   do change resaved in the atomic copy. This should normally not be needed,
-   but if you're seeing issues, please enable this. If your issues stop you
-   being able to resume, enable this option, hibernate and cancel the cycle
-   after the atomic copy is done. If the debugging info shows a non-zero
-   number of pages resaved, please report this to Nigel.
-
-   - compression/algorithm
-
-   Set the cryptoapi algorithm used for compressing the image.
-
-   - compression/expected_compression
-
-   These values allow you to set an expected compression ratio, which TuxOnice
-   will use in calculating whether it meets constraints on the image size. If
-   this expected compression ratio is not attained, the hibernation cycle will
-   abort, so it is wise to allow some spare. You can see what compression
-   ratio is achieved in the logs after hibernating.
-
-   - debug_info:
-
-   This file returns information about your configuration that may be helpful
-   in diagnosing problems with hibernating.
-
-   - did_suspend_to_both:
-
-   This file can be used when you hibernate with powerdown method 3 (ie suspend
-   to ram after writing the image). There can be two outcomes in this case. We
-   can resume from the suspend-to-ram before the battery runs out, or we can run
-   out of juice and and up resuming like normal. This entry lets you find out,
-   post resume, which way we went. If the value is 1, we resumed from suspend
-   to ram. This can be useful when actions need to be run post suspend-to-ram
-   that don't need to be run if we did the normal resume from power off.
-
-   - do_hibernate:
-
-   When anything is written to this file, the kernel side of TuxOnIce will
-   begin to attempt to write an image to disk and power down. You'll normally
-   want to run the hibernate script instead, to get modules unloaded first.
-
-   - do_resume:
-
-   When anything is written to this file TuxOnIce will attempt to read and
-   restore an image. If there is no image, it will return almost immediately.
-   If an image exists, the echo > will never return. Instead, the original
-   kernel context will be restored and the original echo > do_hibernate will
-   return.
-
-   - */enabled
-
-   These option can be used to temporarily disable various parts of TuxOnIce.
-
-   - extra_pages_allowance
-
-   When TuxOnIce does its atomic copy, it calls the driver model suspend
-   and resume methods. If you have DRI enabled with a driver such as fglrx,
-   this can result in the driver allocating a substantial amount of memory
-   for storing its state. Extra_pages_allowance tells TuxOnIce how much
-   extra memory it should ensure is available for those allocations. If
-   your attempts at hibernating end with a message in dmesg indicating that
-   insufficient extra pages were allowed, you need to increase this value.
-
-   - file/target:
-
-   Read this value to get the current setting. Write to it to point TuxOnice
-   at a new storage location for the file allocator. See section 3.b.ii above
-   for details of how to set up the file allocator.
-
-   - freezer_test
-
-   This entry can be used to get TuxOnIce to just test the freezer and prepare
-   an image without actually doing a hibernation cycle. It is useful for
-   diagnosing freezing and image preparation issues.
-
-   - full_pageset2
-
-   TuxOnIce divides the pages that are stored in an image into two sets. The
-   difference between the two sets is that pages in pageset 1 are atomically
-   copied, and pages in pageset 2 are written to disk without being copied
-   first. A page CAN be written to disk without being copied first if and only
-   if its contents will not be modified or used at any time after userspace
-   processes are frozen. A page MUST be in pageset 1 if its contents are
-   modified or used at any time after userspace processes have been frozen.
-
-   Normally (ie if this option is enabled), TuxOnIce will put all pages on the
-   per-zone LRUs in pageset2, then remove those pages used by any userspace
-   user interface helper and TuxOnIce storage manager that are running,
-   together with pages used by the GEM memory manager introduced around 2.6.28
-   kernels.
-
-   If this option is disabled, a much more conservative approach will be taken.
-   The only pages in pageset2 will be those belonging to userspace processes,
-   with the exclusion of those belonging to the TuxOnIce userspace helpers
-   mentioned above. This will result in a much smaller pageset2, and will
-   therefore result in smaller images than are possible with this option
-   enabled.
-
-   - ignore_rootfs
-
-   TuxOnIce records which device is mounted as the root filesystem when
-   writing the hibernation image. It will normally check at resume time that
-   this device isn't already mounted - that would be a cause of filesystem
-   corruption. In some particular cases (RAM based root filesystems), you
-   might want to disable this check. This option allows you to do that.
-
-   - image_exists:
-
-   Can be used in a script to determine whether a valid image exists at the
-   location currently pointed to by resume=. Returns up to three lines.
-   The first is whether an image exists (-1 for unsure, otherwise 0 or 1).
-   If an image eixsts, additional lines will return the machine and version.
-   Echoing anything to this entry removes any current image.
-
-   - image_size_limit:
-
-   The maximum size of hibernation image written to disk, measured in megabytes
-   (1024*1024).
-
-   - last_result:
-
-   The result of the last hibernation cycle, as defined in
-   include/linux/suspend-debug.h with the values SUSPEND_ABORTED to
-   SUSPEND_KEPT_IMAGE. This is a bitmask.
-
-   - late_cpu_hotplug:
-
-   This sysfs entry controls whether cpu hotplugging is done - as normal - just
-   before (unplug) and after (replug) the atomic copy/restore (so that all
-   CPUs/cores are available for multithreaded I/O). The alternative is to
-   unplug all secondary CPUs/cores at the start of hibernating/resuming, and
-   replug them at the end of resuming. No multithreaded I/O will be possible in
-   this configuration, but the odd machine has been reported to require it.
-
-   - lid_file:
-
-   This determines which ACPI button file we look in to determine whether the
-   lid is open or closed after resuming from suspend to disk or power off.
-   If the entry is set to "lid/LID", we'll open /proc/acpi/button/lid/LID/state
-   and check its contents at the appropriate moment. See post_wake_state below
-   for more details on how this entry is used.
-
-   - log_everything (CONFIG_PM_DEBUG):
-
-   Setting this option results in all messages printed being logged. Normally,
-   only a subset are logged, so as to not slow the process and not clutter the
-   logs. Useful for debugging. It can be toggled during a cycle by pressing
-   'L'.
-
-   - no_load_direct:
-
-   This is a debugging option. If, when loading the atomically copied pages of
-   an image, TuxOnIce finds that the destination address for a page is free,
-   it will normally allocate the image, load the data directly into that
-   address and skip it in the atomic restore. If this option is disabled, the
-   page will be loaded somewhere else and atomically restored like other pages.
-
-   - no_flusher_thread:
-
-   When doing multithreaded I/O (see below), the first online CPU can be used
-   to _just_ submit compressed pages when writing the image, rather than
-   compressing and submitting data. This option is normally disabled, but has
-   been included because Nigel would like to see whether it will be more useful
-   as the number of cores/cpus in computers increases.
-
-   - no_multithreaded_io:
-
-   TuxOnIce will normally create one thread per cpu/core on your computer,
-   each of which will then perform I/O. This will generally result in
-   throughput that's the maximum the storage medium can handle. There
-   shouldn't be any reason to disable multithreaded I/O now, but this option
-   has been retained for debugging purposes.
-
-   - no_pageset2
-
-   See the entry for full_pageset2 above for an explanation of pagesets.
-   Enabling this option causes TuxOnIce to do an atomic copy of all pages,
-   thereby limiting the maximum image size to 1/2 of memory, as swsusp does.
-
-   - no_pageset2_if_unneeded
-
-   See the entry for full_pageset2 above for an explanation of pagesets.
-   Enabling this option causes TuxOnIce to act like no_pageset2 was enabled
-   if and only it isn't needed anyway. This option may still make TuxOnIce
-   less reliable because pageset2 pages are normally used to store the
-   atomic copy - drivers that want to do allocations of larger amounts of
-   memory in one shot will be more likely to find that those amounts aren't
-   available if this option is enabled.
-
-   - pause_between_steps (CONFIG_PM_DEBUG):
-
-   This option is used during debugging, to make TuxOnIce pause between
-   each step of the process. It is ignored when the nice display is on.
-
-   - post_wake_state:
-
-   TuxOnIce provides support for automatically waking after a user-selected
-   delay, and using a different powerdown method if the lid is still closed.
-   (Yes, we're assuming a laptop).  This entry lets you choose what state
-   should be entered next. The values are those described under
-   powerdown_method, below. It can be used to suspend to RAM after hibernating,
-   then powerdown properly (say) 20 minutes. It can also be used to power down
-   properly, then wake at (say) 6.30am and suspend to RAM until you're ready
-   to use the machine.
-
-   - powerdown_method:
-
-   Used to select a method by which TuxOnIce should powerdown after writing the
-   image. Currently:
-
-   0: Don't use ACPI to power off.
-   3: Attempt to enter Suspend-to-ram.
-   4: Attempt to enter ACPI S4 mode.
-   5: Attempt to power down via ACPI S5 mode.
-
-   Note that these options are highly dependant upon your hardware & software:
-
-   3: When succesful, your machine suspends to ram instead of powering off.
-      The advantage of using this mode is that it doesn't matter whether your
-      battery has enough charge to make it through to your next resume. If it
-      lasts, you will simply resume from suspend to ram (and the image on disk
-      will be discarded). If the battery runs out, you will resume from disk
-      instead. The disadvantage is that it takes longer than a normal
-      suspend-to-ram to enter the state, since the suspend-to-disk image needs
-      to be written first.
-   4/5: When successful, your machine will be off and comsume (almost) no power.
-      But it might still react to some external events like opening the lid or
-      trafic on  a network or usb device. For the bios, resume is then the same
-      as warm boot, similar to a situation where you used the command `reboot'
-      to reboot your machine. If your machine has problems on warm boot or if
-      you want to protect your machine with the bios password, this is probably
-      not the right choice. Mode 4 may be necessary on some machines where ACPI
-      wake up methods need to be run to properly reinitialise hardware after a
-      hibernation cycle.
-   0: Switch the machine completely off. The only possible wakeup is the power
-      button. For the bios, resume is then the same as a cold boot, in
-      particular you would  have to provide your bios boot password if your
-      machine uses that feature for booting.
-
-   - progressbar_granularity_limit:
-
-   This option can be used to limit the granularity of the progress bar
-   displayed with a bootsplash screen. The value is the maximum number of
-   steps. That is, 10 will make the progress bar jump in 10% increments.
-
-   - reboot:
-
-   This option causes TuxOnIce to reboot rather than powering down
-   at the end of saving an image. It can be toggled during a cycle by pressing
-   'R'.
-
-   - resume:
-
-   This sysfs entry can be used to read and set the location in which TuxOnIce
-   will look for the signature of an image - the value set using resume= at
-   boot time or CONFIG_PM_STD_PARTITION ("Default resume partition"). By
-   writing to this file as well as modifying your bootloader's configuration
-   file (eg menu.lst), you can set or reset the location of your image or the
-   method of storing the image without rebooting.
-
-   - replace_swsusp (CONFIG_TOI_REPLACE_SWSUSP):
-
-   This option makes
-
-     echo disk > /sys/power/state
-
-   activate TuxOnIce instead of swsusp. Regardless of whether this option is
-   enabled, any invocation of swsusp's resume time trigger will cause TuxOnIce
-   to check for an image too. This is due to the fact that at resume time, we
-   can't know whether this option was enabled until we see if an image is there
-   for us to resume from. (And when an image exists, we don't care whether we
-   did replace swsusp anyway - we just want to resume).
-
-   - resume_commandline:
-
-   This entry can be read after resuming to see the commandline that was used
-   when resuming began. You might use this to set up two bootloader entries
-   that are the same apart from the fact that one includes a extra append=
-   argument "at_work=1". You could then grep resume_commandline in your
-   post-resume scripts and configure networking (for example) differently
-   depending upon whether you're at home or work. resume_commandline can be
-   set to arbitrary text if you wish to remove sensitive contents.
-
-   - swap/swapfilename:
-
-   This entry is used to specify the swapfile or partition that
-   TuxOnIce will attempt to swapon/swapoff automatically. Thus, if
-   I normally use /dev/hda1 for swap, and want to use /dev/hda2 for specifically
-   for my hibernation image, I would
-
-   echo /dev/hda2 > /sys/power/tuxonice/swap/swapfile
-
-   /dev/hda2 would then be automatically swapon'd and swapoff'd. Note that the
-   swapon and swapoff occur while other processes are frozen (including kswapd)
-   so this swap file will not be used up when attempting to free memory. The
-   parition/file is also given the highest priority, so other swapfiles/partitions
-   will only be used to save the image when this one is filled.
-
-   The value of this file is used by headerlocations along with any currently
-   activated swapfiles/partitions.
-
-   - swap/headerlocations:
-
-   This option tells you the resume= options to use for swap devices you
-   currently have activated. It is particularly useful when you only want to
-   use a swap file to store your image. See above for further details.
-
-   - test_bio
-
-   This is a debugging option. When enabled, TuxOnIce will not hibernate.
-   Instead, when asked to write an image, it will skip the atomic copy,
-   just doing the writing of the image and then returning control to the
-   user at the point where it would have powered off. This is useful for
-   testing throughput in different configurations.
-
-   - test_filter_speed
-
-   This is a debugging option. When enabled, TuxOnIce will not hibernate.
-   Instead, when asked to write an image, it will not write anything or do
-   an atomic copy, but will only run any enabled compression algorithm on the
-   data that would have been written (the source pages of the atomic copy in
-   the case of pageset 1). This is useful for comparing the performance of
-   compression algorithms and for determining the extent to which an upgrade
-   to your storage method would improve hibernation speed.
-
-   - user_interface/debug_sections (CONFIG_PM_DEBUG):
-
-   This value, together with the console log level, controls what debugging
-   information is displayed. The console log level determines the level of
-   detail, and this value determines what detail is displayed. This value is
-   a bit vector, and the meaning of the bits can be found in the kernel tree
-   in include/linux/tuxonice.h. It can be overridden using the kernel's
-   command line option suspend_dbg.
-
-   - user_interface/default_console_level (CONFIG_PM_DEBUG):
-
-   This determines the value of the console log level at the start of a
-   hibernation cycle. If debugging is compiled in, the console log level can be
-   changed during a cycle by pressing the digit keys. Meanings are:
-
-   0: Nice display.
-   1: Nice display plus numerical progress.
-   2: Errors only.
-   3: Low level debugging info.
-   4: Medium level debugging info.
-   5: High level debugging info.
-   6: Verbose debugging info.
-
-   - user_interface/enable_escape:
-
-   Setting this to "1" will enable you abort a hibernation cycle or resuming by
-   pressing escape, "0" (default) disables this feature. Note that enabling
-   this option means that you cannot initiate a hibernation cycle and then walk
-   away from your computer, expecting it to be secure. With feature disabled,
-   you can validly have this expectation once TuxOnice begins to write the
-   image to disk. (Prior to this point, it is possible that TuxOnice might
-   about because of failure to freeze all processes or because constraints
-   on its ability to save the image are not met).
-
-   - user_interface/program
-
-   This entry is used to tell TuxOnice what userspace program to use for
-   providing a user interface while hibernating. The program uses a netlink
-   socket to pass messages back and forward to the kernel, allowing all of the
-   functions formerly implemented in the kernel user interface components.
-
-   - version:
-
-   The version of TuxOnIce you have compiled into the currently running kernel.
-
-   - wake_alarm_dir:
-
-   As mentioned above (post_wake_state), TuxOnIce supports automatically waking
-   after some delay. This entry allows you to select which wake alarm to use.
-   It should contain the value "rtc0" if you're wanting to use
-   /sys/class/rtc/rtc0.
-
-   - wake_delay:
-
-   This value determines the delay from the end of writing the image until the
-   wake alarm is triggered. You can set an absolute time by writing the desired
-   time into /sys/class/rtc/<wake_alarm_dir>/wakealarm and leaving these values
-   empty.
-
-   Note that for the wakeup to actually occur, you may need to modify entries
-   in /proc/acpi/wakeup. This is done by echoing the name of the button in the
-   first column (eg PBTN) into the file.
-
-7. How do you get support?
-
-   Glad you asked. TuxOnIce is being actively maintained and supported
-   by Nigel (the guy doing most of the kernel coding at the moment), Bernard
-   (who maintains the hibernate script and userspace user interface components)
-   and its users.
-
-   Resources availble include HowTos, FAQs and a Wiki, all available via
-   tuxonice.net.  You can find the mailing lists there.
-
-8. I think I've found a bug. What should I do?
-
-   By far and a way, the most common problems people have with TuxOnIce
-   related to drivers not having adequate power management support. In this
-   case, it is not a bug with TuxOnIce, but we can still help you. As we
-   mentioned above, such issues can usually be worked around by building the
-   functionality as modules and unloading them while hibernating. Please visit
-   the Wiki for up-to-date lists of known issues and work arounds.
-
-   If this information doesn't help, try running:
-
-   hibernate --bug-report
-
-   ..and sending the output to the users mailing list.
-
-   Good information on how to provide us with useful information from an
-   oops is found in the file REPORTING-BUGS, in the top level directory
-   of the kernel tree. If you get an oops, please especially note the
-   information about running what is printed on the screen through ksymoops.
-   The raw information is useless.
-
-9. When will XXX be supported?
-
-   If there's a feature missing from TuxOnIce that you'd like, feel free to
-   ask. We try to be obliging, within reason.
-
-   Patches are welcome. Please send to the list.
-
-10. How does it work?
-
-   TuxOnIce does its work in a number of steps.
-
-   a. Freezing system activity.
-
-   The first main stage in hibernating is to stop all other activity. This is
-   achieved in stages. Processes are considered in fours groups, which we will
-   describe in reverse order for clarity's sake: Threads with the PF_NOFREEZE
-   flag, kernel threads without this flag, userspace processes with the
-   PF_SYNCTHREAD flag and all other processes. The first set (PF_NOFREEZE) are
-   untouched by the refrigerator code. They are allowed to run during hibernating
-   and resuming, and are used to support user interaction, storage access or the
-   like. Other kernel threads (those unneeded while hibernating) are frozen last.
-   This leaves us with userspace processes that need to be frozen. When a
-   process enters one of the *_sync system calls, we set a PF_SYNCTHREAD flag on
-   that process for the duration of that call. Processes that have this flag are
-   frozen after processes without it, so that we can seek to ensure that dirty
-   data is synced to disk as quickly as possible in a situation where other
-   processes may be submitting writes at the same time. Freezing the processes
-   that are submitting data stops new I/O from being submitted. Syncthreads can
-   then cleanly finish their work. So the order is:
-
-   - Userspace processes without PF_SYNCTHREAD or PF_NOFREEZE;
-   - Userspace processes with PF_SYNCTHREAD (they won't have NOFREEZE);
-   - Kernel processes without PF_NOFREEZE.
-
-   b. Eating memory.
-
-   For a successful hibernation cycle, you need to have enough disk space to store the
-   image and enough memory for the various limitations of TuxOnIce's
-   algorithm. You can also specify a maximum image size. In order to attain
-   to those constraints, TuxOnIce may 'eat' memory. If, after freezing
-   processes, the constraints aren't met, TuxOnIce will thaw all the
-   other processes and begin to eat memory until its calculations indicate
-   the constraints are met. It will then freeze processes again and recheck
-   its calculations.
-
-   c. Allocation of storage.
-
-   Next, TuxOnIce allocates the storage that will be used to save
-   the image.
-
-   The core of TuxOnIce knows nothing about how or where pages are stored. We
-   therefore request the active allocator (remember you might have compiled in
-   more than one!) to allocate enough storage for our expect image size. If
-   this request cannot be fulfilled, we eat more memory and try again. If it
-   is fulfiled, we seek to allocate additional storage, just in case our
-   expected compression ratio (if any) isn't achieved. This time, however, we
-   just continue if we can't allocate enough storage.
-
-   If these calls to our allocator change the characteristics of the image
-   such that we haven't allocated enough memory, we also loop. (The allocator
-   may well need to allocate space for its storage information).
-
-   d. Write the first part of the image.
-
-   TuxOnIce stores the image in two sets of pages called 'pagesets'.
-   Pageset 2 contains pages on the active and inactive lists; essentially
-   the page cache. Pageset 1 contains all other pages, including the kernel.
-   We use two pagesets for one important reason: We need to make an atomic copy
-   of the kernel to ensure consistency of the image. Without a second pageset,
-   that would limit us to an image that was at most half the amount of memory
-   available. Using two pagesets allows us to store a full image. Since pageset
-   2 pages won't be needed in saving pageset 1, we first save pageset 2 pages.
-   We can then make our atomic copy of the remaining pages using both pageset 2
-   pages and any other pages that are free. While saving both pagesets, we are
-   careful not to corrupt the image. Among other things, we use lowlevel block
-   I/O routines that don't change the pagecache contents.
-
-   The next step, then, is writing pageset 2.
-
-   e. Suspending drivers and storing processor context.
-
-   Having written pageset2, TuxOnIce calls the power management functions to
-   notify drivers of the hibernation, and saves the processor state in preparation
-   for the atomic copy of memory we are about to make.
-
-   f. Atomic copy.
-
-   At this stage, everything else but the TuxOnIce code is halted. Processes
-   are frozen or idling, drivers are quiesced and have stored (ideally and where
-   necessary) their configuration in memory we are about to atomically copy.
-   In our lowlevel architecture specific code, we have saved the CPU state.
-   We can therefore now do our atomic copy before resuming drivers etc.
-
-   g. Save the atomic copy (pageset 1).
-
-   TuxOnice can then write the atomic copy of the remaining pages. Since we
-   have copied the pages into other locations, we can continue to use the
-   normal block I/O routines without fear of corruption our image.
-
-   f. Save the image header.
-
-   Nearly there! We save our settings and other parameters needed for
-   reloading pageset 1 in an 'image header'. We also tell our allocator to
-   serialise its data at this stage, so that it can reread the image at resume
-   time.
-
-   g. Set the image header.
-
-   Finally, we edit the header at our resume= location. The signature is
-   changed by the allocator to reflect the fact that an image exists, and to
-   point to the start of that data if necessary (swap allocator).
-
-   h. Power down.
-
-   Or reboot if we're debugging and the appropriate option is selected.
-
-   Whew!
-
-   Reloading the image.
-   --------------------
-
-   Reloading the image is essentially the reverse of all the above. We load
-   our copy of pageset 1, being careful to choose locations that aren't going
-   to be overwritten as we copy it back (We start very early in the boot
-   process, so there are no other processes to quiesce here). We then copy
-   pageset 1 back to its original location in memory and restore the process
-   context. We are now running with the original kernel. Next, we reload the
-   pageset 2 pages, free the memory and swap used by TuxOnIce, restore
-   the pageset header and restart processes. Sounds easy in comparison to
-   hibernating, doesn't it!
-
-   There is of course more to TuxOnIce than this, but this explanation
-   should be a good start. If there's interest, I'll write further
-   documentation on range pages and the low level I/O.
-
-11. Who wrote TuxOnIce?
-
-   (Answer based on the writings of Florent Chabaud, credits in files and
-   Nigel's limited knowledge; apologies to anyone missed out!)
-
-   The main developers of TuxOnIce have been...
-
-   Gabor Kuti
-   Pavel Machek
-   Florent Chabaud
-   Bernard Blackham
-   Nigel Cunningham
-
-   Significant portions of swsusp, the code in the vanilla kernel which
-   TuxOnIce enhances, have been worked on by Rafael Wysocki. Thanks should
-   also be expressed to him.
-
-   The above mentioned developers have been aided in their efforts by a host
-   of hundreds, if not thousands of testers and people who have submitted bug
-   fixes & suggestions. Of special note are the efforts of Michael Frank, who
-   had his computers repetitively hibernate and resume for literally tens of
-   thousands of cycles and developed scripts to stress the system and test
-   TuxOnIce far beyond the point most of us (Nigel included!) would consider
-   testing. His efforts have contributed as much to TuxOnIce as any of the
-   names above.