1a9030986SAlan SternWhat:		/sys/bus/usb/devices/.../power/level
2a9030986SAlan SternDate:		March 2007
3a9030986SAlan SternKernelVersion:	2.6.21
4a9030986SAlan SternContact:	Alan Stern <stern@rowland.harvard.edu>
5a9030986SAlan SternDescription:
6a9030986SAlan Stern		Each USB device directory will contain a file named
7a9030986SAlan Stern		power/level.  This file holds a power-level setting for
8a9030986SAlan Stern		the device, either "on" or "auto".
9a9030986SAlan Stern
10a9030986SAlan Stern		"on" means that the device is not allowed to autosuspend,
11a9030986SAlan Stern		although normal suspends for system sleep will still
12a9030986SAlan Stern		be honored.  "auto" means the device will autosuspend
13a9030986SAlan Stern		and autoresume in the usual manner, according to the
14a9030986SAlan Stern		capabilities of its driver.
15a9030986SAlan Stern
16a9030986SAlan Stern		During normal use, devices should be left in the "auto"
17a9030986SAlan Stern		level.  The "on" level is meant for administrative uses.
18a9030986SAlan Stern		If you want to suspend a device immediately but leave it
19a9030986SAlan Stern		free to wake up in response to I/O requests, you should
20a9030986SAlan Stern		write "0" to power/autosuspend.
21a9030986SAlan Stern
22a9030986SAlan Stern		Device not capable of proper suspend and resume should be
23a9030986SAlan Stern		left in the "on" level.  Although the USB spec requires
24a9030986SAlan Stern		devices to support suspend/resume, many of them do not.
25a9030986SAlan Stern		In fact so many don't that by default, the USB core
26a9030986SAlan Stern		initializes all non-hub devices in the "on" level.  Some
27a9030986SAlan Stern		drivers may change this setting when they are bound.
28a9030986SAlan Stern
29a9030986SAlan Stern		This file is deprecated and will be removed after 2010.
30a9030986SAlan Stern		Use the power/control file instead; it does exactly the
31a9030986SAlan Stern		same thing.
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