Merge branch 'slab/for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/penber...

[deliverable/linux.git] / Documentation / power / runtime_pm.txt

diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt
index 6c9f5d9aa115d04ee86c5297f5e3051bee31c0b9..71d8fe4e75d3e5301e25037a28d91600d633dba7 100644 (file)
--- 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
-core.
+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
@@ -660,11 +665,6 @@ Subsystems may wish to conserve code space by using the set of generic power
 management callbacks provided by the PM core, defined in
 driver/base/power/generic_ops.c:
 
-  int pm_generic_runtime_idle(struct device *dev);
-    - invoke the ->runtime_idle() callback provided by the driver of this
-      device, if defined, and call pm_runtime_suspend() for this device if the
-      return value is 0 or the callback is not defined
-
   int pm_generic_runtime_suspend(struct device *dev);
     - invoke the ->runtime_suspend() callback provided by the driver of this
       device and return its result, or return -EINVAL if not defined