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+What:           /sys/bus/usb/devices/.../power/level
+Date:           March 2007
+KernelVersion:  2.6.21
+Contact:        Alan Stern <stern@rowland.harvard.edu>
+Description:
+                Each USB device directory will contain a file named
+                power/level.  This file holds a power-level setting for
+                the device, either "on" or "auto".
+
+                "on" means that the device is not allowed to autosuspend,
+                although normal suspends for system sleep will still
+                be honored.  "auto" means the device will autosuspend
+                and autoresume in the usual manner, according to the
+                capabilities of its driver.
+
+                During normal use, devices should be left in the "auto"
+                level.  The "on" level is meant for administrative uses.
+                If you want to suspend a device immediately but leave it
+                free to wake up in response to I/O requests, you should
+                write "0" to power/autosuspend.
+
+                Device not capable of proper suspend and resume should be
+                left in the "on" level.  Although the USB spec requires
+                devices to support suspend/resume, many of them do not.
+                In fact so many don't that by default, the USB core
+                initializes all non-hub devices in the "on" level.  Some
+                drivers may change this setting when they are bound.
+
+                This file is deprecated and will be removed after 2010.
+                Use the power/control file instead; it does exactly the
+                same thing.