1 What: /sys/bus/usb/devices/.../power/persist
4 Contact: Alan Stern <stern@rowland.harvard.edu>
6 If CONFIG_USB_PERSIST is set, then each USB device directory
7 will contain a file named power/persist. The file holds a
8 boolean value (0 or 1) indicating whether or not the
9 "USB-Persist" facility is enabled for the device. Since the
10 facility is inherently dangerous, it is disabled by default
11 for all devices except hubs. For more information, see
12 Documentation/usb/persist.txt.
14 What: /sys/bus/usb/devices/.../power/autosuspend
17 Contact: Alan Stern <stern@rowland.harvard.edu>
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.
27 The autosuspend delay for newly-created devices is set to
28 the value of the usbcore.autosuspend module parameter.
30 What: /sys/bus/usb/device/.../power/connected_duration
33 Contact: Sarah Sharp <sarah.a.sharp@intel.com>
35 If CONFIG_PM_RUNTIME is 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
40 PowerTOP <power@bughost.org>
41 http://www.lesswatts.org/projects/powertop/
43 What: /sys/bus/usb/device/.../power/active_duration
46 Contact: Sarah Sharp <sarah.a.sharp@intel.com>
48 If CONFIG_PM_RUNTIME is 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.
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 <power@bughost.org>
61 http://www.lesswatts.org/projects/powertop/
63 What: /sys/bus/usb/devices/<busnum>-<port[.port]>...:<config num>-<interface num>/supports_autosuspend
66 Contact: Sarah Sharp <sarah.a.sharp@intel.com>
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
77 git://git.moblin.org/users/sarah/usb-pm-tool/
79 What: /sys/bus/usb/device/.../avoid_reset_quirk
81 Contact: Oliver Neukum <oliver@neukum.org>
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
90 What: /sys/bus/usb/devices/.../devnum
91 KernelVersion: since at least 2.6.18
93 Device address on the USB bus.
95 What: /sys/bus/usb/devices/.../bConfigurationValue
96 KernelVersion: since at least 2.6.18
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.
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.
108 Writing -1 will always unconfigure the device.
110 What: /sys/bus/usb/devices/.../busnum
111 KernelVersion: 2.6.22
113 Bus-number of the USB-bus the device is connected to.
115 What: /sys/bus/usb/devices/.../descriptors
116 KernelVersion: 2.6.26
118 Binary file containing cached descriptors of the device. The
119 binary data consists of the device descriptor followed by the
120 descriptors for each configuration of the device.
121 Note that the wTotalLength of the config descriptors can not
122 be trusted, as the device may have a smaller config descriptor
123 than it advertises. The bLength field of each (sub) descriptor
124 can be trusted, and can be used to seek forward one (sub)
125 descriptor at a time until the next config descriptor is found.
126 All descriptors read from this file are in bus-endian format
128 What: /sys/bus/usb/devices/.../speed
129 KernelVersion: since at least 2.6.18
131 Speed the device is connected with to the usb-host in
132 Mbit / second. IE one of 1.5 / 12 / 480 / 5000.