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". 9 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. 15 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. 21 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. 28 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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