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Possible License(s): 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/persist
 18Date:		May 2007
 19KernelVersion:	2.6.23
 20Contact:	Alan Stern <>
 22		If CONFIG_USB_PERSIST is set, then each USB device directory
 23		will contain a file named power/persist.  The file holds a
 24		boolean value (0 or 1) indicating whether or not the
 25		"USB-Persist" facility is enabled for the device.  Since the
 26		facility is inherently dangerous, it is disabled by default
 27		for all devices except hubs.  For more information, see
 28		Documentation/usb/persist.txt.
 30What:		/sys/bus/usb/device/.../power/connected_duration
 31Date:		January 2008
 32KernelVersion:	2.6.25
 33Contact:	Sarah Sharp <>
 35		If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file
 36		is present.  When read, it returns the total time (in msec)
 37		that the USB device has been connected to the machine.  This
 38		file is read-only.
 40		PowerTOP <>
 43What:		/sys/bus/usb/device/.../power/active_duration
 44Date:		January 2008
 45KernelVersion:	2.6.25
 46Contact:	Sarah Sharp <>
 48		If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file
 49		is present.  When read, it returns the total time (in msec)
 50		that the USB device has been active, i.e. not in a suspended
 51		state.  This file is read-only.
 53		Tools can use this file and the connected_duration file to
 54		compute the percentage of time that a device has been active.
 55		For example,
 56		echo $((100 * `cat active_duration` / `cat connected_duration`))
 57		will give an integer percentage.  Note that this does not
 58		account for counter wrap.
 60		PowerTOP <>
 63What:		/sys/bus/usb/device/<busnum>-<devnum>...:<config num>-<interface num>/supports_autosuspend
 64Date:		January 2008
 65KernelVersion:	2.6.27
 66Contact:	Sarah Sharp <>
 68		When read, this file returns 1 if the interface driver
 69		for this interface supports autosuspend.  It also
 70		returns 1 if no driver has claimed this interface, as an
 71		unclaimed interface will not stop the device from being
 72		autosuspended if all other interface drivers are idle.
 73		The file returns 0 if autosuspend support has not been
 74		added to the driver.
 76		USB PM tool
 77		git://
 79What:		/sys/bus/usb/device/.../authorized
 80Date:		July 2008
 81KernelVersion:	2.6.26
 82Contact:	David Vrabel <>
 84		Authorized devices are available for use by device
 85		drivers, non-authorized one are not.  By default, wired
 86		USB devices are authorized.
 88		Certified Wireless USB devices are not authorized
 89		initially and should be (by writing 1) after the
 90		device has been authenticated.
 92What:		/sys/bus/usb/device/.../wusb_cdid
 93Date:		July 2008
 94KernelVersion:	2.6.27
 95Contact:	David Vrabel <>
 97		For Certified Wireless USB devices only.
 99		A devices's CDID, as 16 space-separated hex octets.
101What:		/sys/bus/usb/device/.../wusb_ck
102Date:		July 2008
103KernelVersion:	2.6.27
104Contact:	David Vrabel <>
106		For Certified Wireless USB devices only.
108		Write the device's connection key (CK) to start the
109		authentication of the device.  The CK is 16
110		space-separated hex octets.
112What:		/sys/bus/usb/device/.../wusb_disconnect
113Date:		July 2008
114KernelVersion:	2.6.27
115Contact:	David Vrabel <>
117		For Certified Wireless USB devices only.
119		Write a 1 to force the device to disconnect
120		(equivalent to unplugging a wired USB device).
122What:		/sys/bus/usb/drivers/.../remove_id
123Date:		November 2009
124Contact:	CHENG Renquan <>
126		Writing a device ID to this file will remove an ID
127		that was dynamically added via the new_id sysfs entry.
128		The format for the device ID is:
129		idVendor idProduct.	After successfully
130		removing an ID, the driver will no longer support the
131		device.  This is useful to ensure auto probing won't
132		match the driver to the device.  For example:
133		# echo "046d c315" > /sys/bus/usb/drivers/foo/remove_id
135What:		/sys/bus/usb/device/.../avoid_reset_quirk
136Date:		December 2009
137Contact:	Oliver Neukum <>
139		Writing 1 to this file tells the kernel that this
140		device will morph into another mode when it is reset.
141		Drivers will not use reset for error handling for
142		such devices.
144		usb_modeswitch