1What:		/sys/bus/usb/devices/.../power/persist
2Date:		May 2007
3KernelVersion:	2.6.23
4Contact:	Alan Stern <stern@rowland.harvard.edu>
5Description:
6		USB device directories can contain a file named power/persist.
7		The file holds a boolean value (0 or 1) indicating whether or
8		not the "USB-Persist" facility is enabled for the device.  For
9		hubs this facility is always enabled and their device
10		directories will not contain this file.
11
12		For more information, see Documentation/usb/persist.txt.
13
14What:		/sys/bus/usb/devices/.../power/autosuspend
15Date:		March 2007
16KernelVersion:	2.6.21
17Contact:	Alan Stern <stern@rowland.harvard.edu>
18Description:
19		Each USB device directory will contain a file named
20		power/autosuspend.  This file holds the time (in seconds)
21		the device must be idle before it will be autosuspended.
22		0 means the device will be autosuspended as soon as
23		possible.  Negative values will prevent the device from
24		being autosuspended at all, and writing a negative value
25		will resume the device if it is already suspended.
26
27		The autosuspend delay for newly-created devices is set to
28		the value of the usbcore.autosuspend module parameter.
29
30What:		/sys/bus/usb/device/.../power/connected_duration
31Date:		January 2008
32KernelVersion:	2.6.25
33Contact:	Sarah Sharp <sarah.a.sharp@intel.com>
34Description:
35		If CONFIG_PM is enabled, then this file is present.  When read,
36		it returns the total time (in msec) that the USB device has been
37		connected to the machine.  This file is read-only.
38Users:
39		PowerTOP <powertop@lists.01.org>
40		https://01.org/powertop/
41
42What:		/sys/bus/usb/device/.../power/active_duration
43Date:		January 2008
44KernelVersion:	2.6.25
45Contact:	Sarah Sharp <sarah.a.sharp@intel.com>
46Description:
47		If CONFIG_PM is enabled, then this file is present.  When read,
48		it returns the total time (in msec) that the USB device has been
49		active, i.e. not in a suspended state.  This file is read-only.
50
51		Tools can use this file and the connected_duration file to
52		compute the percentage of time that a device has been active.
53		For example,
54		echo $((100 * `cat active_duration` / `cat connected_duration`))
55		will give an integer percentage.  Note that this does not
56		account for counter wrap.
57Users:
58		PowerTOP <powertop@lists.01.org>
59		https://01.org/powertop/
60
61What:		/sys/bus/usb/devices/<busnum>-<port[.port]>...:<config num>-<interface num>/supports_autosuspend
62Date:		January 2008
63KernelVersion:	2.6.27
64Contact:	Sarah Sharp <sarah.a.sharp@intel.com>
65Description:
66		When read, this file returns 1 if the interface driver
67		for this interface supports autosuspend.  It also
68		returns 1 if no driver has claimed this interface, as an
69		unclaimed interface will not stop the device from being
70		autosuspended if all other interface drivers are idle.
71		The file returns 0 if autosuspend support has not been
72		added to the driver.
73Users:
74		USB PM tool
75		git://git.moblin.org/users/sarah/usb-pm-tool/
76
77What:		/sys/bus/usb/device/.../avoid_reset_quirk
78Date:		December 2009
79Contact:	Oliver Neukum <oliver@neukum.org>
80Description:
81		Writing 1 to this file tells the kernel that this
82		device will morph into another mode when it is reset.
83		Drivers will not use reset for error handling for
84		such devices.
85Users:
86		usb_modeswitch
87
88What:		/sys/bus/usb/devices/.../devnum
89KernelVersion:	since at least 2.6.18
90Description:
91		Device address on the USB bus.
92Users:
93		libusb
94
95What:		/sys/bus/usb/devices/.../bConfigurationValue
96KernelVersion:	since at least 2.6.18
97Description:
98		bConfigurationValue of the *active* configuration for the
99		device. Writing 0 or -1 to bConfigurationValue will reset the
100		active configuration (unconfigure the device). Writing
101		another value will change the active configuration.
102
103		Note that some devices, in violation of the USB spec, have a
104		configuration with a value equal to 0. Writing 0 to
105		bConfigurationValue for these devices will install that
106		configuration, rather then unconfigure the device.
107
108		Writing -1 will always unconfigure the device.
109Users:
110		libusb
111
112What:		/sys/bus/usb/devices/.../busnum
113KernelVersion:	2.6.22
114Description:
115		Bus-number of the USB-bus the device is connected to.
116Users:
117		libusb
118
119What:		/sys/bus/usb/devices/.../descriptors
120KernelVersion:	2.6.26
121Description:
122		Binary file containing cached descriptors of the device. The
123		binary data consists of the device descriptor followed by the
124		descriptors for each configuration of the device.
125		Note that the wTotalLength of the config descriptors can not
126		be trusted, as the device may have a smaller config descriptor
127		than it advertises. The bLength field of each (sub) descriptor
128		can be trusted, and can be used to seek forward one (sub)
129		descriptor at a time until the next config descriptor is found.
130		All descriptors read from this file are in bus-endian format
131Users:
132		libusb
133
134What:		/sys/bus/usb/devices/.../speed
135KernelVersion:	since at least 2.6.18
136Description:
137		Speed the device is connected with to the usb-host in
138		Mbit / second. IE one of 1.5 / 12 / 480 / 5000.
139Users:
140		libusb
141