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PM: runtime: Clarify documentation when callbacks are unassigned

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Recent changes to the PM core allows ->runtime_suspend|resume callbacks to
be unassigned.

In the earlier behaviour the PM core would return -ENOSYS, when trying to
runtime resume a device, for example. Let's update the documentation to
clarify this.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Ulf Hansson 2021-06-09 12:06:10 +02:00 committed by Rafael J. Wysocki
parent 63d00be693
commit 4ec4f05908
1 changed files with 9 additions and 0 deletions
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9
Documentation/power/runtime_pm.rst
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@ -831,6 +831,15 @@ or driver about runtime power changes. Instead, the driver for the device's
parent must take responsibility for telling the device's driver when the
parent's power state changes.
Note that, in some cases it may not be desirable for subsystems/drivers to call
pm_runtime_no_callbacks() for their devices. This could be because a subset of
the runtime PM callbacks needs to be implemented, a platform dependent PM
domain could get attached to the device or that the device is power managed
through a supplier device link. For these reasons and to avoid boilerplate code
in subsystems/drivers, the PM core allows runtime PM callbacks to be
unassigned. More precisely, if a callback pointer is NULL, the PM core will act
as though there was a callback and it returned 0.
9. Autosuspend, or automatically-delayed suspends
=================================================