1eaafbc3aSAlan SternWhat: /sys/bus/usb/devices/.../power/autosuspend 2eaafbc3aSAlan SternDate: March 2007 3eaafbc3aSAlan SternKernelVersion: 2.6.21 4eaafbc3aSAlan SternContact: Alan Stern <stern@rowland.harvard.edu> 5eaafbc3aSAlan SternDescription: 6eaafbc3aSAlan Stern Each USB device directory will contain a file named 7eaafbc3aSAlan Stern power/autosuspend. This file holds the time (in seconds) 8eaafbc3aSAlan Stern the device must be idle before it will be autosuspended. 9eaafbc3aSAlan Stern 0 means the device will be autosuspended as soon as 10eaafbc3aSAlan Stern possible. Negative values will prevent the device from 11eaafbc3aSAlan Stern being autosuspended at all, and writing a negative value 12eaafbc3aSAlan Stern will resume the device if it is already suspended. 13eaafbc3aSAlan Stern 14eaafbc3aSAlan Stern The autosuspend delay for newly-created devices is set to 15eaafbc3aSAlan Stern the value of the usbcore.autosuspend module parameter. 16*2add5229SAlan Stern 17*2add5229SAlan SternWhat: /sys/bus/usb/devices/.../power/level 18*2add5229SAlan SternDate: March 2007 19*2add5229SAlan SternKernelVersion: 2.6.21 20*2add5229SAlan SternContact: Alan Stern <stern@rowland.harvard.edu> 21*2add5229SAlan SternDescription: 22*2add5229SAlan Stern Each USB device directory will contain a file named 23*2add5229SAlan Stern power/level. This file holds a power-level setting for 24*2add5229SAlan Stern the device, one of "on", "auto", or "suspend". 25*2add5229SAlan Stern 26*2add5229SAlan Stern "on" means that the device is not allowed to autosuspend, 27*2add5229SAlan Stern although normal suspends for system sleep will still 28*2add5229SAlan Stern be honored. "auto" means the device will autosuspend 29*2add5229SAlan Stern and autoresume in the usual manner, according to the 30*2add5229SAlan Stern capabilities of its driver. "suspend" means the device 31*2add5229SAlan Stern is forced into a suspended state and it will not autoresume 32*2add5229SAlan Stern in response to I/O requests. However remote-wakeup requests 33*2add5229SAlan Stern from the device may still be enabled (the remote-wakeup 34*2add5229SAlan Stern setting is controlled separately by the power/wakeup 35*2add5229SAlan Stern attribute). 36*2add5229SAlan Stern 37*2add5229SAlan Stern During normal use, devices should be left in the "auto" 38*2add5229SAlan Stern level. The other levels are meant for administrative uses. 39*2add5229SAlan Stern If you want to suspend a device immediately but leave it 40*2add5229SAlan Stern free to wake up in response to I/O requests, you should 41*2add5229SAlan Stern write "0" to power/autosuspend. 42