1*a9030986SAlan SternWhat: /sys/bus/usb/devices/.../power/level 2*a9030986SAlan SternDate: March 2007 3*a9030986SAlan SternKernelVersion: 2.6.21 4*a9030986SAlan SternContact: Alan Stern <stern@rowland.harvard.edu> 5*a9030986SAlan SternDescription: 6*a9030986SAlan Stern Each USB device directory will contain a file named 7*a9030986SAlan Stern power/level. This file holds a power-level setting for 8*a9030986SAlan Stern the device, either "on" or "auto". 9*a9030986SAlan Stern 10*a9030986SAlan Stern "on" means that the device is not allowed to autosuspend, 11*a9030986SAlan Stern although normal suspends for system sleep will still 12*a9030986SAlan Stern be honored. "auto" means the device will autosuspend 13*a9030986SAlan Stern and autoresume in the usual manner, according to the 14*a9030986SAlan Stern capabilities of its driver. 15*a9030986SAlan Stern 16*a9030986SAlan Stern During normal use, devices should be left in the "auto" 17*a9030986SAlan Stern level. The "on" level is meant for administrative uses. 18*a9030986SAlan Stern If you want to suspend a device immediately but leave it 19*a9030986SAlan Stern free to wake up in response to I/O requests, you should 20*a9030986SAlan Stern write "0" to power/autosuspend. 21*a9030986SAlan Stern 22*a9030986SAlan Stern Device not capable of proper suspend and resume should be 23*a9030986SAlan Stern left in the "on" level. Although the USB spec requires 24*a9030986SAlan Stern devices to support suspend/resume, many of them do not. 25*a9030986SAlan Stern In fact so many don't that by default, the USB core 26*a9030986SAlan Stern initializes all non-hub devices in the "on" level. Some 27*a9030986SAlan Stern drivers may change this setting when they are bound. 28*a9030986SAlan Stern 29*a9030986SAlan Stern This file is deprecated and will be removed after 2010. 30*a9030986SAlan Stern Use the power/control file instead; it does exactly the 31*a9030986SAlan Stern same thing. 32