What:		/sys/bus/usb/devices/.../power/autosuspend
Date:		March 2007
KernelVersion:	2.6.21
Contact:	Alan Stern <stern@rowland.harvard.edu>
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/persist
Date:		May 2007
KernelVersion:	2.6.23
Contact:	Alan Stern <stern@rowland.harvard.edu>
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 <sarah.a.sharp@intel.com>
Description:
		If CONFIG_PM_RUNTIME is 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 <power@bughost.org>
		http://www.lesswatts.org/projects/powertop/

What:		/sys/bus/usb/device/.../power/active_duration
Date:		January 2008
KernelVersion:	2.6.25
Contact:	Sarah Sharp <sarah.a.sharp@intel.com>
Description:
		If CONFIG_PM_RUNTIME is 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 <power@bughost.org>
		http://www.lesswatts.org/projects/powertop/

What:		/sys/bus/usb/device/<busnum>-<devnum>...:<config num>-<interface num>/supports_autosuspend
Date:		January 2008
KernelVersion:	2.6.27
Contact:	Sarah Sharp <sarah.a.sharp@intel.com>
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/

What:		/sys/bus/usb/device/.../authorized
Date:		July 2008
KernelVersion:	2.6.26
Contact:	David Vrabel <david.vrabel@csr.com>
Description:
		Authorized devices are available for use by device
		drivers, non-authorized one are not.  By default, wired
		USB devices are authorized.

		Certified Wireless USB devices are not authorized
		initially and should be (by writing 1) after the
		device has been authenticated.

What:		/sys/bus/usb/device/.../wusb_cdid
Date:		July 2008
KernelVersion:	2.6.27
Contact:	David Vrabel <david.vrabel@csr.com>
Description:
		For Certified Wireless USB devices only.

		A devices's CDID, as 16 space-separated hex octets.

What:		/sys/bus/usb/device/.../wusb_ck
Date:		July 2008
KernelVersion:	2.6.27
Contact:	David Vrabel <david.vrabel@csr.com>
Description:
		For Certified Wireless USB devices only.

		Write the device's connection key (CK) to start the
		authentication of the device.  The CK is 16
		space-separated hex octets.

What:		/sys/bus/usb/device/.../wusb_disconnect
Date:		July 2008
KernelVersion:	2.6.27
Contact:	David Vrabel <david.vrabel@csr.com>
Description:
		For Certified Wireless USB devices only.

		Write a 1 to force the device to disconnect
		(equivalent to unplugging a wired USB device).

What:		/sys/bus/usb/drivers/.../new_id
Date:		October 2011
Contact:	linux-usb@vger.kernel.org
Description:
		Writing a device ID to this file will attempt to
		dynamically add a new device ID to a USB device driver.
		This may allow the driver to support more hardware than
		was included in the driver's static device ID support
		table at compile time. The format for the device ID is:
		idVendor idProduct bInterfaceClass.
		The vendor ID and device ID fields are required, the
		interface class is optional.
		Upon successfully adding an ID, the driver will probe
		for the device and attempt to bind to it.  For example:
		# echo "8086 10f5" > /sys/bus/usb/drivers/foo/new_id

		Reading from this file will list all dynamically added
		device IDs in the same format, with one entry per
		line. For example:
		# cat /sys/bus/usb/drivers/foo/new_id
		8086 10f5
		dead beef 06
		f00d cafe

		The list will be truncated at PAGE_SIZE bytes due to
		sysfs restrictions.

What:		/sys/bus/usb-serial/drivers/.../new_id
Date:		October 2011
Contact:	linux-usb@vger.kernel.org
Description:
		For serial USB drivers, this attribute appears under the
		extra bus folder "usb-serial" in sysfs; apart from that
		difference, all descriptions from the entry
		"/sys/bus/usb/drivers/.../new_id" apply.

What:		/sys/bus/usb/drivers/.../remove_id
Date:		November 2009
Contact:	CHENG Renquan <rqcheng@smu.edu.sg>
Description:
		Writing a device ID to this file will remove an ID
		that was dynamically added via the new_id sysfs entry.
		The format for the device ID is:
		idVendor idProduct.	After successfully
		removing an ID, the driver will no longer support the
		device.  This is useful to ensure auto probing won't
		match the driver to the device.  For example:
		# echo "046d c315" > /sys/bus/usb/drivers/foo/remove_id

		Reading from this file will list the dynamically added
		device IDs, exactly like reading from the entry
		"/sys/bus/usb/drivers/.../new_id"

What:		/sys/bus/usb/device/.../avoid_reset_quirk
Date:		December 2009
Contact:	Oliver Neukum <oliver@neukum.org>
Description:
		Writing 1 to this file tells the kernel that this
		device will morph into another mode when it is reset.
		Drivers will not use reset for error handling for
		such devices.
Users:
		usb_modeswitch

What:		/sys/bus/usb/devices/.../power/usb2_hardware_lpm
Date:		September 2011
Contact:	Andiry Xu <andiry.xu@amd.com>
Description:
		If CONFIG_PM_RUNTIME is set and a USB 2.0 lpm-capable device
		is plugged in to a xHCI host which support link PM, it will
		perform a LPM test; if the test is passed and host supports
		USB2 hardware LPM (xHCI 1.0 feature), USB2 hardware LPM will
		be enabled for the device and the USB device directory will
		contain a file named power/usb2_hardware_lpm.  The file holds
		a string value (enable or disable) indicating whether or not
		USB2 hardware LPM is enabled for the device. Developer can
		write y/Y/1 or n/N/0 to the file to enable/disable the
		feature.

What:		/sys/bus/usb/devices/.../removable
Date:		February 2012
Contact:	Matthew Garrett <mjg@redhat.com>
Description:
		Some information about whether a given USB device is
		physically fixed to the platform can be inferred from a
		combination of hub descriptor bits and platform-specific data
		such as ACPI. This file will read either "removable" or
		"fixed" if the information is available, and "unknown"
		otherwise.

What:		/sys/bus/usb/devices/.../ltm_capable
Date:		July 2012
Contact:	Sarah Sharp <sarah.a.sharp@linux.intel.com>
Description:
		USB 3.0 devices may optionally support Latency Tolerance
		Messaging (LTM).  They indicate their support by setting a bit
		in the bmAttributes field of their SuperSpeed BOS descriptors.
		If that bit is set for the device, ltm_capable will read "yes".
		If the device doesn't support LTM, the file will read "no".
		The file will be present for all speeds of USB devices, and will
		always read "no" for USB 1.1 and USB 2.0 devices.

What:		/sys/bus/usb/devices/.../(hub interface)/portX
Date:		August 2012
Contact:	Lan Tianyu <tianyu.lan@intel.com>
Description:
		The /sys/bus/usb/devices/.../(hub interface)/portX
		is usb port device's sysfs directory.

What:		/sys/bus/usb/devices/.../(hub interface)/portX/connect_type
Date:		January 2013
Contact:	Lan Tianyu <tianyu.lan@intel.com>
Description:
		Some platforms provide usb port connect types through ACPI.
		This attribute is to expose these information to user space.
		The file will read "hotplug", "wired" and "not used" if the
		information is available, and "unknown" otherwise.

What:		/sys/bus/usb/devices/.../power/usb2_lpm_l1_timeout
Date:		May 2013
Contact:	Mathias Nyman <mathias.nyman@linux.intel.com>
Description:
		USB 2.0 devices may support hardware link power management (LPM)
		L1 sleep state. The usb2_lpm_l1_timeout attribute allows
		tuning the timeout for L1 inactivity timer (LPM timer), e.g.
		needed inactivity time before host requests the device to go to L1 sleep.
		Useful for power management tuning.
		Supported values are 0 - 65535 microseconds.

What:		/sys/bus/usb/devices/.../power/usb2_lpm_besl
Date:		May 2013
Contact:	Mathias Nyman <mathias.nyman@linux.intel.com>
Description:
		USB 2.0 devices that support hardware link power management (LPM)
		L1 sleep state now use a best effort service latency value (BESL) to
		indicate the best effort to resumption of service to the device after the
		initiation of the resume event.
		If the device does not have a preferred besl value then the host can select
		one instead. This usb2_lpm_besl attribute allows to tune the host selected besl
		value in order to tune power saving and service latency.

		Supported values are 0 - 15.
		More information on how besl values map to microseconds can be found in
		USB 2.0 ECN Errata for Link Power Management, section 4.10)
