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PM: Update documentation regarding sysdevs 

The part of Documentation/power/devices.txt regarding sysdevs is not
valid any more after commit 2e711c04db
(PM: Remove sysdev suspend, resume and shutdown operations), so
remove it.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
This commit is contained in:
Rafael J. Wysocki 2011-06-18 19:53:57 +02:00
parent 129b656a0d
commit 78420884e6
1 changed files with 0 additions and 26 deletions
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26
Documentation/power/devices.txt
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@ -549,32 +549,6 @@ callbacks. The other platforms need not implement it or take it into account
in any way.
System Devices
--------------
System devices (sysdevs) follow a slightly different API, which can be found in
include/linux/sysdev.h
drivers/base/sys.c
System devices will be suspended with interrupts disabled, and after all other
devices have been suspended. On resume, they will be resumed before any other
devices, and also with interrupts disabled. These things occur in special
"sysdev_driver" phases, which affect only system devices.
Thus, after the suspend_noirq (or freeze_noirq or poweroff_noirq) phase, when
the non-boot CPUs are all offline and IRQs are disabled on the remaining online
CPU, then a sysdev_driver.suspend phase is carried out, and the system enters a
sleep state (or a system image is created). During resume (or after the image
has been created or loaded) a sysdev_driver.resume phase is carried out, IRQs
are enabled on the only online CPU, the non-boot CPUs are enabled, and the
resume_noirq (or thaw_noirq or restore_noirq) phase begins.
Code to actually enter and exit the system-wide low power state sometimes
involves hardware details that are only known to the boot firmware, and
may leave a CPU running software (from SRAM or flash memory) that monitors
the system and manages its wakeup sequence.
Device Low Power (suspend) States
---------------------------------
Device low-power states aren't standard. One device might only handle