162306a36Sopenharmony_ciWhat: /sys/bus/usb/devices/.../power/level 262306a36Sopenharmony_ciDate: March 2007 362306a36Sopenharmony_ciKernelVersion: 2.6.21 462306a36Sopenharmony_ciContact: Alan Stern <stern@rowland.harvard.edu> 562306a36Sopenharmony_ciDescription: 662306a36Sopenharmony_ci Each USB device directory will contain a file named 762306a36Sopenharmony_ci power/level. This file holds a power-level setting for 862306a36Sopenharmony_ci the device, either "on" or "auto". 962306a36Sopenharmony_ci 1062306a36Sopenharmony_ci "on" means that the device is not allowed to autosuspend, 1162306a36Sopenharmony_ci although normal suspends for system sleep will still 1262306a36Sopenharmony_ci be honored. "auto" means the device will autosuspend 1362306a36Sopenharmony_ci and autoresume in the usual manner, according to the 1462306a36Sopenharmony_ci capabilities of its driver. 1562306a36Sopenharmony_ci 1662306a36Sopenharmony_ci During normal use, devices should be left in the "auto" 1762306a36Sopenharmony_ci level. The "on" level is meant for administrative uses. 1862306a36Sopenharmony_ci If you want to suspend a device immediately but leave it 1962306a36Sopenharmony_ci free to wake up in response to I/O requests, you should 2062306a36Sopenharmony_ci write "0" to power/autosuspend. 2162306a36Sopenharmony_ci 2262306a36Sopenharmony_ci Device not capable of proper suspend and resume should be 2362306a36Sopenharmony_ci left in the "on" level. Although the USB spec requires 2462306a36Sopenharmony_ci devices to support suspend/resume, many of them do not. 2562306a36Sopenharmony_ci In fact so many don't that by default, the USB core 2662306a36Sopenharmony_ci initializes all non-hub devices in the "on" level. Some 2762306a36Sopenharmony_ci drivers may change this setting when they are bound. 2862306a36Sopenharmony_ci 2962306a36Sopenharmony_ci This file is deprecated and will be removed after 2010. 3062306a36Sopenharmony_ci Use the power/control file instead; it does exactly the 3162306a36Sopenharmony_ci same thing. 32