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authorUlf Hansson <ulf.hansson@linaro.org>2021-06-09 13:06:10 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2021-06-11 20:04:07 +0300
commit4ec4f059088b48585c337328e05fa930c64d1ba8 (patch)
tree63e4cc76e0df069ac1eed5c085e80f89158913b6 /Documentation/power
parent63d00be69348fda431ae59aba6af268a5cf5058e (diff)
downloadlinux-4ec4f059088b48585c337328e05fa930c64d1ba8.tar.xz
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 <ulf.hansson@linaro.org> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/power')
-rw-r--r--Documentation/power/runtime_pm.rst9
1 files changed, 9 insertions, 0 deletions
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
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