From 4ec4f059088b48585c337328e05fa930c64d1ba8 Mon Sep 17 00:00:00 2001 From: Ulf Hansson Date: Wed, 9 Jun 2021 12:06:10 +0200 Subject: PM: runtime: Clarify documentation when callbacks are unassigned 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 Acked-by: Alan Stern Signed-off-by: Rafael J. Wysocki --- Documentation/power/runtime_pm.rst | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'Documentation/power') diff --git a/Documentation/power/runtime_pm.rst b/Documentation/power/runtime_pm.rst index b48cac5f9048..d6bf84f061f4 100644 --- a/Documentation/power/runtime_pm.rst +++ b/Documentation/power/runtime_pm.rst @@ -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 ================================================= -- cgit v1.2.3