PM: Add facility for advanced testing of async suspend/resume
Add configuration switch CONFIG_PM_ADVANCED_DEBUG for compiling in
extra PM debugging/testing code allowing one to access some
PM-related attributes of devices from the user space via sysfs.
If CONFIG_PM_ADVANCED_DEBUG is set, add sysfs attribute power/async
for every device allowing the user space to access the device's
power.async_suspend flag and modify it, if desired.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
diff --git a/Documentation/ABI/testing/sysfs-devices-power b/Documentation/ABI/testing/sysfs-devices-power
index 431bfd7..6123c52 100644
--- a/Documentation/ABI/testing/sysfs-devices-power
+++ b/Documentation/ABI/testing/sysfs-devices-power
@@ -51,3 +51,29 @@
drivers. Changing this attribute to "on" prevents the driver
from power managing the device at run time. Doing that while
the device is suspended causes it to be woken up.
+
+What: /sys/devices/.../power/async
+Date: January 2009
+Contact: Rafael J. Wysocki <rjw@sisk.pl>
+Description:
+ The /sys/devices/.../async attribute allows the user space to
+ enable or diasble the device's suspend and resume callbacks to
+ be executed asynchronously (ie. in separate threads, in parallel
+ with the main suspend/resume thread) during system-wide power
+ transitions (eg. suspend to RAM, hibernation).
+
+ All devices have one of the following two values for the
+ power/async file:
+
+ + "enabled\n" to permit the asynchronous suspend/resume;
+ + "disabled\n" to forbid it;
+
+ The value of this attribute may be changed by writing either
+ "enabled", or "disabled" to it.
+
+ It generally is unsafe to permit the asynchronous suspend/resume
+ of a device unless it is certain that all of the PM dependencies
+ of the device are known to the PM core. However, for some
+ devices this attribute is set to "enabled" by bus type code or
+ device drivers and in that cases it should be safe to leave the
+ default value.