What:		/sys/bus/usb/devices/.../power/persist
Date:		May 2007
KernelVersion:	2.6.23
Contact:	Alan Stern <stern@rowland.harvard.edu>
Description:
		USB device directories can 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.  For
		hubs this facility is always enabled and their device
		directories will not contain this file.

		For more information, see Documentation/driver-api/usb/persist.rst.

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/device/.../power/connected_duration
Date:		January 2008
KernelVersion:	2.6.25
Contact:	Sarah Sharp <sarah.a.sharp@intel.com>
Description:
		If CONFIG_PM 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 <powertop@lists.01.org>
		https://01.org/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 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 <powertop@lists.01.org>
		https://01.org/powertop/

What:		/sys/bus/usb/devices/<busnum>-<port[.port]>...:<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/.../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/.../devnum
KernelVersion:	since at least 2.6.18
Description:
		Device address on the USB bus.
Users:
		libusb

What:		/sys/bus/usb/devices/.../bConfigurationValue
KernelVersion:	since at least 2.6.18
Description:
		bConfigurationValue of the *active* configuration for the
		device. Writing 0 or -1 to bConfigurationValue will reset the
		active configuration (unconfigure the device). Writing
		another value will change the active configuration.

		Note that some devices, in violation of the USB spec, have a
		configuration with a value equal to 0. Writing 0 to
		bConfigurationValue for these devices will install that
		configuration, rather then unconfigure the device.

		Writing -1 will always unconfigure the device.
Users:
		libusb

What:		/sys/bus/usb/devices/.../busnum
KernelVersion:	2.6.22
Description:
		Bus-number of the USB-bus the device is connected to.
Users:
		libusb

What:		/sys/bus/usb/devices/.../descriptors
KernelVersion:	2.6.26
Description:
		Binary file containing cached descriptors of the device. The
		binary data consists of the device descriptor followed by the
		descriptors for each configuration of the device.
		Note that the wTotalLength of the config descriptors can not
		be trusted, as the device may have a smaller config descriptor
		than it advertises. The bLength field of each (sub) descriptor
		can be trusted, and can be used to seek forward one (sub)
		descriptor at a time until the next config descriptor is found.
		All descriptors read from this file are in bus-endian format
Users:
		libusb

What:		/sys/bus/usb/devices/.../speed
KernelVersion:	since at least 2.6.18
Description:
		Speed the device is connected with to the usb-host in
		Mbit / second. IE one of 1.5 / 12 / 480 / 5000.
Users:
		libusb
