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Based on kernel version 3.19. Page generated on 2015-02-13 21:15 EST.

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