Now, to use the userland interface for software suspend you need special
utilities that will read/write the system memory snapshot from/to the
kernel. Such utilities are available, for example, from
-<http://www.sisk.pl/kernel/utilities/suspend>. You may want to have
-a look at them if you are going to develop your own suspend/resume
-utilities.
+<http://suspend.sourceforge.net>. You may want to have a look at them if you
+are going to develop your own suspend/resume utilities.
The interface consists of a character device providing the open(),
release(), read(), and write() operations as well as several ioctl()
-commands defined in kernel/power/power.h. The major and minor
+commands defined in include/linux/suspend_ioctls.h . The major and minor
numbers of the device are, respectively, 10 and 231, and they can
be read from /sys/class/misc/snapshot/dev.
The device can be open either for reading or for writing. If open for
reading, it is considered to be in the suspend mode. Otherwise it is
-assumed to be in the resume mode. The device cannot be open for reading
-and writing. It is also impossible to have the device open more than once
-at a time.
+assumed to be in the resume mode. The device cannot be open for simultaneous
+reading and writing. It is also impossible to have the device open more than
+once at a time.
The ioctl() commands recognized by the device are:
SNAPSHOT_FREEZE - freeze user space processes (the current process is
- not frozen); this is required for SNAPSHOT_ATOMIC_SNAPSHOT
+ not frozen); this is required for SNAPSHOT_CREATE_IMAGE
and SNAPSHOT_ATOMIC_RESTORE to succeed
SNAPSHOT_UNFREEZE - thaw user space processes frozen by SNAPSHOT_FREEZE
-SNAPSHOT_ATOMIC_SNAPSHOT - create a snapshot of the system memory; the
+SNAPSHOT_CREATE_IMAGE - create a snapshot of the system memory; the
last argument of ioctl() should be a pointer to an int variable,
the value of which will indicate whether the call returned after
creating the snapshot (1) or after restoring the system memory state
from it (0) (after resume the system finds itself finishing the
- SNAPSHOT_ATOMIC_SNAPSHOT ioctl() again); after the snapshot
+ SNAPSHOT_CREATE_IMAGE ioctl() again); after the snapshot
has been created the read() operation can be used to transfer
it out of the kernel
SNAPSHOT_FREE - free memory allocated for the snapshot image
-SNAPSHOT_SET_IMAGE_SIZE - set the preferred maximum size of the image
+SNAPSHOT_PREF_IMAGE_SIZE - set the preferred maximum size of the image
(the kernel will do its best to ensure the image size will not exceed
this number, but if it turns out to be impossible, the kernel will
create the smallest image possible)
-SNAPSHOT_AVAIL_SWAP - return the amount of available swap in bytes (the last
- argument should be a pointer to an unsigned int variable that will
+SNAPSHOT_GET_IMAGE_SIZE - return the actual size of the hibernation image
+
+SNAPSHOT_AVAIL_SWAP_SIZE - return the amount of available swap in bytes (the
+ last argument should be a pointer to an unsigned int variable that will
contain the result if the call is successful).
-SNAPSHOT_GET_SWAP_PAGE - allocate a swap page from the resume partition
+SNAPSHOT_ALLOC_SWAP_PAGE - allocate a swap page from the resume partition
(the last argument should be a pointer to a loff_t variable that
will contain the swap page offset if the call is successful)
-SNAPSHOT_FREE_SWAP_PAGES - free all swap pages allocated with
- SNAPSHOT_GET_SWAP_PAGE
-
-SNAPSHOT_SET_SWAP_FILE - set the resume partition (the last ioctl() argument
- should specify the device's major and minor numbers in the old
- two-byte format, as returned by the stat() function in the .st_rdev
- member of the stat structure); it is recommended to always use this
- call, because the code to set the resume partition could be removed from
- future kernels
+SNAPSHOT_FREE_SWAP_PAGES - free all swap pages allocated by
+ SNAPSHOT_ALLOC_SWAP_PAGE
+
+SNAPSHOT_SET_SWAP_AREA - set the resume partition and the offset (in <PAGE_SIZE>
+ units) from the beginning of the partition at which the swap header is
+ located (the last ioctl() argument should point to a struct
+ resume_swap_area, as defined in kernel/power/suspend_ioctls.h,
+ containing the resume device specification and the offset); for swap
+ partitions the offset is always 0, but it is different from zero for
+ swap files (see Documentation/swsusp-and-swap-files.txt for details).
+
+SNAPSHOT_PLATFORM_SUPPORT - enable/disable the hibernation platform support,
+ depending on the argument value (enable, if the argument is nonzero)
+
+SNAPSHOT_POWER_OFF - make the kernel transition the system to the hibernation
+ state (eg. ACPI S4) using the platform (eg. ACPI) driver
+
+SNAPSHOT_S2RAM - suspend to RAM; using this call causes the kernel to
+ immediately enter the suspend-to-RAM state, so this call must always
+ be preceded by the SNAPSHOT_FREEZE call and it is also necessary
+ to use the SNAPSHOT_UNFREEZE call after the system wakes up. This call
+ is needed to implement the suspend-to-both mechanism in which the
+ suspend image is first created, as though the system had been suspended
+ to disk, and then the system is suspended to RAM (this makes it possible
+ to resume the system from RAM if there's enough battery power or restore
+ its state on the basis of the saved suspend image otherwise)
The device's read() operation can be used to transfer the snapshot image from
the kernel. It has the following limitations:
into the kernel. It has the same limitations as the read() operation.
The release() operation frees all memory allocated for the snapshot image
-and all swap pages allocated with SNAPSHOT_GET_SWAP_PAGE (if any).
+and all swap pages allocated with SNAPSHOT_ALLOC_SWAP_PAGE (if any).
Thus it is not necessary to use either SNAPSHOT_FREE or
SNAPSHOT_FREE_SWAP_PAGES before closing the device (in fact it will also
unfreeze user space processes frozen by SNAPSHOT_UNFREEZE if they are
still frozen when the device is being closed).
Currently it is assumed that the userland utilities reading/writing the
-snapshot image from/to the kernel will use a swap partition, called the resume
-partition, as storage space. However, this is not really required, as they
-can use, for example, a special (blank) suspend partition or a file on a partition
-that is unmounted before SNAPSHOT_ATOMIC_SNAPSHOT and mounted afterwards.
-
-These utilities SHOULD NOT make any assumptions regarding the ordering of
-data within the snapshot image, except for the image header that MAY be
-assumed to start with an swsusp_info structure, as specified in
-kernel/power/power.h. This structure MAY be used by the userland utilities
-to obtain some information about the snapshot image, such as the size
-of the snapshot image, including the metadata and the header itself,
-contained in the .size member of swsusp_info.
+snapshot image from/to the kernel will use a swap parition, called the resume
+partition, or a swap file as storage space (if a swap file is used, the resume
+partition is the partition that holds this file). However, this is not really
+required, as they can use, for example, a special (blank) suspend partition or
+a file on a partition that is unmounted before SNAPSHOT_CREATE_IMAGE and
+mounted afterwards.
+
+These utilities MUST NOT make any assumptions regarding the ordering of
+data within the snapshot image. The contents of the image are entirely owned
+by the kernel and its structure may be changed in future kernel releases.
The snapshot image MUST be written to the kernel unaltered (ie. all of the image
data, metadata and header MUST be written in _exactly_ the same amount, form
The suspending and resuming utilities MUST lock themselves in memory,
preferrably using mlockall(), before calling SNAPSHOT_FREEZE.
-The suspending utility MUST check the value stored by SNAPSHOT_ATOMIC_SNAPSHOT
+The suspending utility MUST check the value stored by SNAPSHOT_CREATE_IMAGE
in the memory location pointed to by the last argument of ioctl() and proceed
in accordance with it:
1. If the value is 1 (ie. the system memory snapshot has just been
image has been saved.
(b) The suspending utility SHOULD NOT attempt to perform any
file system operations (including reads) on the file systems
- that were mounted before SNAPSHOT_ATOMIC_SNAPSHOT has been
+ that were mounted before SNAPSHOT_CREATE_IMAGE has been
called. However, it MAY mount a file system that was not
mounted at that time and perform some operations on it (eg.
use it for saving the image).
git.openpandora.org / pandora-kernel.git / blobdiff