What: /sys/bus/usb/devices/.../power/autosuspend Date: March 2007 KernelVersion: 2.6.21 Contact: Alan Stern Description: Each USB device directory will contain a file named power/autosuspend. This file holds the time (in seconds) the device must be idle before it will be autosuspended. 0 means the device will be autosuspended as soon as possible. Negative values will prevent the device from being autosuspended at all, and writing a negative value will resume the device if it is already suspended. The autosuspend delay for newly-created devices is set to the value of the usbcore.autosuspend module parameter. What: /sys/bus/usb/devices/.../power/level Date: March 2007 KernelVersion: 2.6.21 Contact: Alan Stern Description: Each USB device directory will contain a file named power/level. This file holds a power-level setting for the device, one of "on", "auto", or "suspend". "on" means that the device is not allowed to autosuspend, although normal suspends for system sleep will still be honored. "auto" means the device will autosuspend and autoresume in the usual manner, according to the capabilities of its driver. "suspend" means the device is forced into a suspended state and it will not autoresume in response to I/O requests. However remote-wakeup requests from the device may still be enabled (the remote-wakeup setting is controlled separately by the power/wakeup attribute). During normal use, devices should be left in the "auto" level. The other levels are meant for administrative uses. If you want to suspend a device immediately but leave it free to wake up in response to I/O requests, you should write "0" to power/autosuspend. What: /sys/bus/usb/devices/.../power/persist Date: May 2007 KernelVersion: 2.6.23 Contact: Alan Stern Description: If CONFIG_USB_PERSIST is set, then each USB device directory will contain a file named power/persist. The file holds a boolean value (0 or 1) indicating whether or not the "USB-Persist" facility is enabled for the device. Since the facility is inherently dangerous, it is disabled by default for all devices except hubs. For more information, see Documentation/usb/persist.txt. What: /sys/bus/usb/device/.../power/connected_duration Date: January 2008 KernelVersion: 2.6.25 Contact: Sarah Sharp Description: If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file is present. When read, it returns the total time (in msec) that the USB device has been connected to the machine. This file is read-only. Users: PowerTOP http://www.lesswatts.org/projects/powertop/ What: /sys/bus/usb/device/.../power/active_duration Date: January 2008 KernelVersion: 2.6.25 Contact: Sarah Sharp Description: If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file is present. When read, it returns the total time (in msec) that the USB device has been active, i.e. not in a suspended state. This file is read-only. Tools can use this file and the connected_duration file to compute the percentage of time that a device has been active. For example, echo $((100 * `cat active_duration` / `cat connected_duration`)) will give an integer percentage. Note that this does not account for counter wrap. Users: PowerTOP http://www.lesswatts.org/projects/powertop/ What: /sys/bus/usb/device/-...:-/supports_autosuspend Date: January 2008 KernelVersion: 2.6.27 Contact: Sarah Sharp Description: When read, this file returns 1 if the interface driver for this interface supports autosuspend. It also returns 1 if no driver has claimed this interface, as an unclaimed interface will not stop the device from being autosuspended if all other interface drivers are idle. The file returns 0 if autosuspend support has not been added to the driver. Users: USB PM tool git://git.moblin.org/users/sarah/usb-pm-tool/