path: root/Documentation/power
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authorAlan Stern <stern@rowland.harvard.edu>2013-06-03 21:49:59 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-06-03 21:49:59 +0200
commit43d51af489126305dbacc1b8ebd1ce4797d277ea (patch)
tree9e100cee2754cab3e367ba39636fcac775e06c3b /Documentation/power
parent45f0a85c8258741d11bda25c0a5669c06267204a (diff)
PM / Runtime: Update .runtime_idle() callback documentation
Runtime PM documentation needs to be updated after the previous change of the rpm_idle() behavior, so modify it as appropriate. [rjw: Subject and changelog] Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/power')
1 files changed, 10 insertions, 5 deletions
diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt
index 6c470c71ba27..71d8fe4e75d3 100644
--- a/Documentation/power/runtime_pm.txt
+++ b/Documentation/power/runtime_pm.txt
@@ -144,8 +144,12 @@ The action performed by the idle callback is totally dependent on the subsystem
(or driver) in question, but the expected and recommended action is to check
if the device can be suspended (i.e. if all of the conditions necessary for
suspending the device are satisfied) and to queue up a suspend request for the
-device in that case. The value returned by this callback is ignored by the PM
+device in that case. If there is no idle callback, or if the callback returns
+0, then the PM core will attempt to carry out a runtime suspend of the device;
+in essence, it will call pm_runtime_suspend() directly. To prevent this (for
+example, if the callback routine has started a delayed suspend), the routine
+should return a non-zero value. Negative error return codes are ignored by the
+PM core.
The helper functions provided by the PM core, described in Section 4, guarantee
that the following constraints are met with respect to runtime PM callbacks for
@@ -301,9 +305,10 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
removing the device from device hierarchy
int pm_runtime_idle(struct device *dev);
- - execute the subsystem-level idle callback for the device; returns 0 on
- success or error code on failure, where -EINPROGRESS means that
- ->runtime_idle() is already being executed
+ - execute the subsystem-level idle callback for the device; returns an
+ error code on failure, where -EINPROGRESS means that ->runtime_idle() is
+ already being executed; if there is no callback or the callback returns 0
+ then run pm_runtime_suspend(dev) and return its result
int pm_runtime_suspend(struct device *dev);
- execute the subsystem-level suspend callback for the device; returns 0 on

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