diff options
Diffstat (limited to 'Documentation/power/userland-swsusp.txt')
| -rw-r--r-- | Documentation/power/userland-swsusp.txt | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/Documentation/power/userland-swsusp.txt b/Documentation/power/userland-swsusp.txt index 7b99636564c..0e870825c1b 100644 --- a/Documentation/power/userland-swsusp.txt +++ b/Documentation/power/userland-swsusp.txt @@ -24,6 +24,10 @@ 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. +Even opening the device has side effects. Data structures are +allocated, and PM_HIBERNATION_PREPARE / PM_RESTORE_PREPARE chains are +called. + The ioctl() commands recognized by the device are: SNAPSHOT_FREEZE - freeze user space processes (the current process is @@ -73,7 +77,8 @@ SNAPSHOT_SET_SWAP_AREA - set the resume partition and the offset (in <PAGE_SIZE> 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). + swap files (see Documentation/power/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) @@ -94,7 +99,7 @@ SNAPSHOT_S2RAM - suspend to RAM; using this call causes the kernel to The device's read() operation can be used to transfer the snapshot image from the kernel. It has the following limitations: - you cannot read() more than one virtual memory page at a time -- read()s accross page boundaries are impossible (ie. if ypu read() 1/2 of +- read()s across page boundaries are impossible (ie. if ypu read() 1/2 of a page in the previous call, you will only be able to read() _at_ _most_ 1/2 of the page in the next call) @@ -109,7 +114,7 @@ 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 parition, called the resume +snapshot image from/to the kernel will use a swap partition, 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 @@ -133,7 +138,7 @@ mechanism and the userland utilities using the interface SHOULD use additional means, such as checksums, to ensure the integrity of the snapshot image. The suspending and resuming utilities MUST lock themselves in memory, -preferrably using mlockall(), before calling SNAPSHOT_FREEZE. +preferably using mlockall(), before calling SNAPSHOT_FREEZE. 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 @@ -143,7 +148,7 @@ in accordance with it: (a) The suspending utility MUST NOT close the snapshot device _unless_ the whole suspend procedure is to be cancelled, in which case, if the snapshot image has already been saved, the - suspending utility SHOULD destroy it, preferrably by zapping + suspending utility SHOULD destroy it, preferably by zapping its header. If the suspend is not to be cancelled, the system MUST be powered off or rebooted after the snapshot image has been saved. |