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. 162add5229SAlan Stern 172add5229SAlan SternWhat: /sys/bus/usb/devices/.../power/level 182add5229SAlan SternDate: March 2007 192add5229SAlan SternKernelVersion: 2.6.21 202add5229SAlan SternContact: Alan Stern <stern@rowland.harvard.edu> 212add5229SAlan SternDescription: 222add5229SAlan Stern Each USB device directory will contain a file named 232add5229SAlan Stern power/level. This file holds a power-level setting for 242add5229SAlan Stern the device, one of "on", "auto", or "suspend". 252add5229SAlan Stern 262add5229SAlan Stern "on" means that the device is not allowed to autosuspend, 272add5229SAlan Stern although normal suspends for system sleep will still 282add5229SAlan Stern be honored. "auto" means the device will autosuspend 292add5229SAlan Stern and autoresume in the usual manner, according to the 302add5229SAlan Stern capabilities of its driver. "suspend" means the device 312add5229SAlan Stern is forced into a suspended state and it will not autoresume 322add5229SAlan Stern in response to I/O requests. However remote-wakeup requests 332add5229SAlan Stern from the device may still be enabled (the remote-wakeup 342add5229SAlan Stern setting is controlled separately by the power/wakeup 352add5229SAlan Stern attribute). 362add5229SAlan Stern 372add5229SAlan Stern During normal use, devices should be left in the "auto" 382add5229SAlan Stern level. The other levels are meant for administrative uses. 392add5229SAlan Stern If you want to suspend a device immediately but leave it 402add5229SAlan Stern free to wake up in response to I/O requests, you should 412add5229SAlan Stern write "0" to power/autosuspend. 42*b41a60ecSAlan Stern 43*b41a60ecSAlan SternWhat: /sys/bus/usb/devices/.../power/persist 44*b41a60ecSAlan SternDate: May 2007 45*b41a60ecSAlan SternKernelVersion: 2.6.23 46*b41a60ecSAlan SternContact: Alan Stern <stern@rowland.harvard.edu> 47*b41a60ecSAlan SternDescription: 48*b41a60ecSAlan Stern If CONFIG_USB_PERSIST is set, then each USB device directory 49*b41a60ecSAlan Stern will contain a file named power/persist. The file holds a 50*b41a60ecSAlan Stern boolean value (0 or 1) indicating whether or not the 51*b41a60ecSAlan Stern "USB-Persist" facility is enabled for the device. Since the 52*b41a60ecSAlan Stern facility is inherently dangerous, it is disabled by default 53*b41a60ecSAlan Stern for all devices except hubs. For more information, see 54*b41a60ecSAlan Stern Documentation/usb/persist.txt. 55