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/driver-api/usb/persist.rst.
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
55		  echo $((100 * `cat active_duration` / `cat connected_duration`))
56
57		will give an integer percentage.  Note that this does not
58		account for counter wrap.
59Users:
60		PowerTOP <powertop@lists.01.org>
61		https://01.org/powertop/
62
63What:		/sys/bus/usb/devices/<busnum>-<port[.port]>...:<config num>-<interface num>/supports_autosuspend
64Date:		January 2008
65KernelVersion:	2.6.27
66Contact:	Sarah Sharp <sarah.a.sharp@intel.com>
67Description:
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.
75Users:
76		USB PM tool
77		git://git.moblin.org/users/sarah/usb-pm-tool/
78
79What:		/sys/bus/usb/device/.../avoid_reset_quirk
80Date:		December 2009
81Contact:	Oliver Neukum <oliver@neukum.org>
82Description:
83		Writing 1 to this file tells the kernel that this
84		device will morph into another mode when it is reset.
85		Drivers will not use reset for error handling for
86		such devices.
87Users:
88		usb_modeswitch
89
90What:		/sys/bus/usb/devices/.../devnum
91KernelVersion:	since at least 2.6.18
92Description:
93		Device address on the USB bus.
94Users:
95		libusb
96
97What:		/sys/bus/usb/devices/.../bConfigurationValue
98KernelVersion:	since at least 2.6.18
99Description:
100		bConfigurationValue of the *active* configuration for the
101		device. Writing 0 or -1 to bConfigurationValue will reset the
102		active configuration (unconfigure the device). Writing
103		another value will change the active configuration.
104
105		Note that some devices, in violation of the USB spec, have a
106		configuration with a value equal to 0. Writing 0 to
107		bConfigurationValue for these devices will install that
108		configuration, rather then unconfigure the device.
109
110		Writing -1 will always unconfigure the device.
111Users:
112		libusb
113
114What:		/sys/bus/usb/devices/.../busnum
115KernelVersion:	2.6.22
116Description:
117		Bus-number of the USB-bus the device is connected to.
118Users:
119		libusb
120
121What:		/sys/bus/usb/devices/.../descriptors
122KernelVersion:	2.6.26
123Description:
124		Binary file containing cached descriptors of the device. The
125		binary data consists of the device descriptor followed by the
126		descriptors for each configuration of the device.
127		Note that the wTotalLength of the config descriptors can not
128		be trusted, as the device may have a smaller config descriptor
129		than it advertises. The bLength field of each (sub) descriptor
130		can be trusted, and can be used to seek forward one (sub)
131		descriptor at a time until the next config descriptor is found.
132		All descriptors read from this file are in bus-endian format
133Users:
134		libusb
135
136What:		/sys/bus/usb/devices/.../speed
137KernelVersion:	since at least 2.6.18
138Description:
139		Speed the device is connected with to the usb-host in
140		Mbit / second. IE one of 1.5 / 12 / 480 / 5000.
141Users:
142		libusb
143