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Possible License(s): CC-BY-SA-3.0, GPL-2.0, LGPL-2.0, AGPL-1.0
  1What:		/sys/bus/usb/devices/.../power/autosuspend
  2Date:		March 2007
  3KernelVersion:	2.6.21
  4Contact:	Alan Stern <>
  6		Each USB device directory will contain a file named
  7		power/autosuspend.  This file holds the time (in seconds)
  8		the device must be idle before it will be autosuspended.
  9		0 means the device will be autosuspended as soon as
 10		possible.  Negative values will prevent the device from
 11		being autosuspended at all, and writing a negative value
 12		will resume the device if it is already suspended.
 14		The autosuspend delay for newly-created devices is set to
 15		the value of the usbcore.autosuspend module parameter.
 17What:		/sys/bus/usb/devices/.../power/level
 18Date:		March 2007
 19KernelVersion:	2.6.21
 20Contact:	Alan Stern <>
 22		Each USB device directory will contain a file named
 23		power/level.  This file holds a power-level setting for
 24		the device, either "on" or "auto".
 26		"on" means that the device is not allowed to autosuspend,
 27		although normal suspends for system sleep will still
 28		be honored.  "auto" means the device will autosuspend
 29		and autoresume in the usual manner, according to the
 30		capabilities of its driver.
 32		During normal use, devices should be left in the "auto"
 33		level.  The "on" level is meant for administrative uses.
 34		If you want to suspend a device immediately but leave it
 35		free to wake up in response to I/O requests, you should
 36		write "0" to power/autosuspend.
 38		Device not capable of proper suspend and resume should be
 39		left in the "on" level.  Although the USB spec requires
 40		devices to support suspend/resume, many of them do not.
 41		In fact so many don't that by default, the USB core
 42		initializes all non-hub devices in the "on" level.  Some
 43		drivers may change this setting when they are bound.
 45What:		/sys/bus/usb/devices/.../power/persist
 46Date:		May 2007
 47KernelVersion:	2.6.23
 48Contact:	Alan Stern <>
 50		If CONFIG_USB_PERSIST is set, then each USB device directory
 51		will contain a file named power/persist.  The file holds a
 52		boolean value (0 or 1) indicating whether or not the
 53		"USB-Persist" facility is enabled for the device.  Since the
 54		facility is inherently dangerous, it is disabled by default
 55		for all devices except hubs.  For more information, see
 56		Documentation/usb/persist.txt.
 58What:		/sys/bus/usb/device/.../power/connected_duration
 59Date:		January 2008
 60KernelVersion:	2.6.25
 61Contact:	Sarah Sharp <>
 63		If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file
 64		is present.  When read, it returns the total time (in msec)
 65		that the USB device has been connected to the machine.  This
 66		file is read-only.
 68		PowerTOP <>
 71What:		/sys/bus/usb/device/.../power/active_duration
 72Date:		January 2008
 73KernelVersion:	2.6.25
 74Contact:	Sarah Sharp <>
 76		If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file
 77		is present.  When read, it returns the total time (in msec)
 78		that the USB device has been active, i.e. not in a suspended
 79		state.  This file is read-only.
 81		Tools can use this file and the connected_duration file to
 82		compute the percentage of time that a device has been active.
 83		For example,
 84		echo $((100 * `cat active_duration` / `cat connected_duration`))
 85		will give an integer percentage.  Note that this does not
 86		account for counter wrap.
 88		PowerTOP <>
 91What:		/sys/bus/usb/device/<busnum>-<devnum>...:<config num>-<interface num>/supports_autosuspend
 92Date:		January 2008
 93KernelVersion:	2.6.27
 94Contact:	Sarah Sharp <>
 96		When read, this file returns 1 if the interface driver
 97		for this interface supports autosuspend.  It also
 98		returns 1 if no driver has claimed this interface, as an
 99		unclaimed interface will not stop the device from being
100		autosuspended if all other interface drivers are idle.
101		The file returns 0 if autosuspend support has not been
102		added to the driver.
104		USB PM tool
105		git://
107What:		/sys/bus/usb/device/.../authorized
108Date:		July 2008
109KernelVersion:	2.6.26
110Contact:	David Vrabel <>
112		Authorized devices are available for use by device
113		drivers, non-authorized one are not.  By default, wired
114		USB devices are authorized.
116		Certified Wireless USB devices are not authorized
117		initially and should be (by writing 1) after the
118		device has been authenticated.
120What:		/sys/bus/usb/device/.../wusb_cdid
121Date:		July 2008
122KernelVersion:	2.6.27
123Contact:	David Vrabel <>
125		For Certified Wireless USB devices only.
127		A devices's CDID, as 16 space-separated hex octets.
129What:		/sys/bus/usb/device/.../wusb_ck
130Date:		July 2008
131KernelVersion:	2.6.27
132Contact:	David Vrabel <>
134		For Certified Wireless USB devices only.
136		Write the device's connection key (CK) to start the
137		authentication of the device.  The CK is 16
138		space-separated hex octets.
140What:		/sys/bus/usb/device/.../wusb_disconnect
141Date:		July 2008
142KernelVersion:	2.6.27
143Contact:	David Vrabel <>
145		For Certified Wireless USB devices only.
147		Write a 1 to force the device to disconnect
148		(equivalent to unplugging a wired USB device).
150What:		/sys/bus/usb/drivers/.../remove_id
151Date:		November 2009
152Contact:	CHENG Renquan <>
154		Writing a device ID to this file will remove an ID
155		that was dynamically added via the new_id sysfs entry.
156		The format for the device ID is:
157		idVendor idProduct.	After successfully
158		removing an ID, the driver will no longer support the
159		device.  This is useful to ensure auto probing won't
160		match the driver to the device.  For example:
161		# echo "046d c315" > /sys/bus/usb/drivers/foo/remove_id
163What:		/sys/bus/usb/device/.../avoid_reset_quirk
164Date:		December 2009
165Contact:	Oliver Neukum <>
167		Writing 1 to this file tells the kernel that this
168		device will morph into another mode when it is reset.
169		Drivers will not use reset for error handling for
170		such devices.
172		usb_modeswitch