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1What: /sys/bus/usb/devices/.../power/persist2Date: May 20073KernelVersion: 2.6.234Contact: 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 or8 not the "USB-Persist" facility is enabled for the device. For9 hubs this facility is always enabled and their device10 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/autosuspend15Date: March 200716KernelVersion: 2.6.2117Contact: Alan Stern <stern@rowland.harvard.edu>18Description:19 Each USB device directory will contain a file named20 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 as23 possible. Negative values will prevent the device from24 being autosuspended at all, and writing a negative value25 will resume the device if it is already suspended.26 27 The autosuspend delay for newly-created devices is set to28 the value of the usbcore.autosuspend module parameter.29 30What: /sys/bus/usb/device/.../power/connected_duration31Date: January 200832KernelVersion: 2.6.2533Contact: 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 been37 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_duration43Date: January 200844KernelVersion: 2.6.2545Contact: 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 been49 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 to52 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 not58 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_autosuspend64Date: January 200865KernelVersion: 2.6.2766Contact: Sarah Sharp <sarah.a.sharp@intel.com>67Description:68 When read, this file returns 1 if the interface driver69 for this interface supports autosuspend. It also70 returns 1 if no driver has claimed this interface, as an71 unclaimed interface will not stop the device from being72 autosuspended if all other interface drivers are idle.73 The file returns 0 if autosuspend support has not been74 added to the driver.75Users:76 USB PM tool77 git://git.moblin.org/users/sarah/usb-pm-tool/78 79What: /sys/bus/usb/device/.../avoid_reset_quirk80Date: December 200981Contact: Oliver Neukum <oliver@neukum.org>82Description:83 Writing 1 to this file tells the kernel that this84 device will morph into another mode when it is reset.85 Drivers will not use reset for error handling for86 such devices.87Users:88 usb_modeswitch89 90What: /sys/bus/usb/devices/.../devnum91KernelVersion: since at least 2.6.1892Description:93 Device address on the USB bus.94Users:95 libusb96 97What: /sys/bus/usb/devices/.../bConfigurationValue98KernelVersion: since at least 2.6.1899Description:100 bConfigurationValue of the *active* configuration for the101 device. Writing 0 or -1 to bConfigurationValue will reset the102 active configuration (unconfigure the device). Writing103 another value will change the active configuration.104 105 Note that some devices, in violation of the USB spec, have a106 configuration with a value equal to 0. Writing 0 to107 bConfigurationValue for these devices will install that108 configuration, rather then unconfigure the device.109 110 Writing -1 will always unconfigure the device.111Users:112 libusb113 114What: /sys/bus/usb/devices/.../busnum115KernelVersion: 2.6.22116Description:117 Bus-number of the USB-bus the device is connected to.118Users:119 libusb120 121What: /sys/bus/usb/devices/.../descriptors122KernelVersion: 2.6.26123Description:124 Binary file containing cached descriptors of the device. The125 binary data consists of the device descriptor followed by the126 descriptors for each configuration of the device.127 Note that the wTotalLength of the config descriptors can not128 be trusted, as the device may have a smaller config descriptor129 than it advertises. The bLength field of each (sub) descriptor130 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 format133Users:134 libusb135 136What: /sys/bus/usb/devices/.../speed137KernelVersion: since at least 2.6.18138Description:139 Speed the device is connected with to the usb-host in140 Mbit / second. IE one of 1.5 / 12 / 480 / 5000.141Users:142 libusb143