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PM: Add comment describing relationships between PM callbacks to pm.h

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The UNIVERSAL_DEV_PM_OPS() macro is slightly misleading, because it
may suggest that it's a good idea to point runtime PM callback
pointers to the same routines as system suspend/resume callbacks
.suspend() and .resume(), which is not the case.  For this reason,
add a comment to include/linux/pm.h, next to the definition of
UNIVERSAL_DEV_PM_OPS(), describing how device PM callbacks are
related to each other.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
This commit is contained in:
Rafael J. Wysocki 2012-02-13 16:29:47 +01:00
parent bc25cf5089
commit c48825251c
1 changed files with 9 additions and 0 deletions
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9
include/linux/pm.h
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@ -320,6 +320,15 @@ const struct dev_pm_ops name = { \
/*
* Use this for defining a set of PM operations to be used in all situations
* (sustem suspend, hibernation or runtime PM).
* NOTE: In general, system suspend callbacks, .suspend() and .resume(), should
* be different from the corresponding runtime PM callbacks, .runtime_suspend(),
* and .runtime_resume(), because .runtime_suspend() always works on an already
* quiescent device, while .suspend() should assume that the device may be doing
* something when it is called (it should ensure that the device will be
* quiescent after it has returned). Therefore it's better to point the "late"
* suspend and "early" resume callback pointers, .suspend_late() and
* .resume_early(), to the same routines as .runtime_suspend() and
* .runtime_resume(), respectively (and analogously for hibernation).
*/
#define UNIVERSAL_DEV_PM_OPS(name, suspend_fn, resume_fn, idle_fn) \
const struct dev_pm_ops name = { \