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()
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_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
+ member of the stat structure)
+
+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/power.h, containing the
+ resume device specification, as for the SNAPSHOT_SET_SWAP_FILE ioctl(),
+ and the offset); for swap partitions the offset is always 0, but it is
+ different to zero for swap files (please see
+ Documentation/swsusp-and-swap-files.txt for details).
+ The SNAPSHOT_SET_SWAP_AREA ioctl() is considered as a replacement for
+ SNAPSHOT_SET_SWAP_FILE which is regarded as obsolete. It is
+ recommended to always use this call, because the code to set the resume
+ partition may be removed from future kernels
+
+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)
+
+SNAPSHOT_PMOPS - enable the usage of the pmops->prepare, pmops->enter and
+ pmops->finish methods (the in-kernel swsusp knows these as the "platform
+ method") which are needed on many machines to (among others) speed up
+ the resume by letting the BIOS skip some steps or to let the system
+ recognise the correct state of the hardware after the resume (in
+ particular on many machines this ensures that unplugged AC
+ adapters get correctly detected and that kacpid does not run wild after
+ the resume). The last ioctl() argument can take one of the three
+ values, defined in kernel/power/power.h:
+ PMOPS_PREPARE - make the kernel carry out the
+ pm_ops->prepare(PM_SUSPEND_DISK) operation
+ PMOPS_ENTER - make the kernel power off the system by calling
+ pm_ops->enter(PM_SUSPEND_DISK)
+ PMOPS_FINISH - make the kernel carry out the
+ pm_ops->finish(PM_SUSPEND_DISK) operation
The device's read() operation can be used to transfer the snapshot image from
the kernel. It has the following limitations:
Currently it is assumed that the userland utilities reading/writing the
snapshot image from/to the kernel will use a swap parition, 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.
+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_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
git.samba.org / sfrench / cifs-2.6.git / blobdiff