1What: /sys/bus/usb/devices/.../power/autosuspend 2Date: March 2007 3KernelVersion: 2.6.21 4Contact: Alan Stern <stern@rowland.harvard.edu> 5Description: 6 Each USB device directory will contain a file named 7 power/autosuspend. This file holds the time (in seconds) 8 the device must be idle before it will be autosuspended. 9 0 means the device will be autosuspended as soon as 10 possible. Negative values will prevent the device from 11 being autosuspended at all, and writing a negative value 12 will resume the device if it is already suspended. 13 14 The autosuspend delay for newly-created devices is set to 15 the value of the usbcore.autosuspend module parameter. 16 17What: /sys/bus/usb/devices/.../power/level 18Date: March 2007 19KernelVersion: 2.6.21 20Contact: Alan Stern <stern@rowland.harvard.edu> 21Description: 22 Each USB device directory will contain a file named 23 power/level. This file holds a power-level setting for 24 the device, either "on" or "auto". 25 26 "on" means that the device is not allowed to autosuspend, 27 although normal suspends for system sleep will still 28 be honored. "auto" means the device will autosuspend 29 and autoresume in the usual manner, according to the 30 capabilities of its driver. 31 32 During normal use, devices should be left in the "auto" 33 level. The "on" level is meant for administrative uses. 34 If you want to suspend a device immediately but leave it 35 free to wake up in response to I/O requests, you should 36 write "0" to power/autosuspend. 37 38 Device not capable of proper suspend and resume should be 39 left in the "on" level. Although the USB spec requires 40 devices to support suspend/resume, many of them do not. 41 In fact so many don't that by default, the USB core 42 initializes all non-hub devices in the "on" level. Some 43 drivers may change this setting when they are bound. 44 45What: /sys/bus/usb/devices/.../power/persist 46Date: May 2007 47KernelVersion: 2.6.23 48Contact: Alan Stern <stern@rowland.harvard.edu> 49Description: 50 If CONFIG_USB_PERSIST is set, then each USB device directory 51 will contain a file named power/persist. The file holds a 52 boolean value (0 or 1) indicating whether or not the 53 "USB-Persist" facility is enabled for the device. Since the 54 facility is inherently dangerous, it is disabled by default 55 for all devices except hubs. For more information, see 56 Documentation/usb/persist.txt. 57 58What: /sys/bus/usb/device/.../power/connected_duration 59Date: January 2008 60KernelVersion: 2.6.25 61Contact: Sarah Sharp <sarah.a.sharp@intel.com> 62Description: 63 If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file 64 is present. When read, it returns the total time (in msec) 65 that the USB device has been connected to the machine. This 66 file is read-only. 67Users: 68 PowerTOP <power@bughost.org> 69 http://www.lesswatts.org/projects/powertop/ 70 71What: /sys/bus/usb/device/.../power/active_duration 72Date: January 2008 73KernelVersion: 2.6.25 74Contact: Sarah Sharp <sarah.a.sharp@intel.com> 75Description: 76 If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file 77 is present. When read, it returns the total time (in msec) 78 that the USB device has been active, i.e. not in a suspended 79 state. This file is read-only. 80 81 Tools can use this file and the connected_duration file to 82 compute the percentage of time that a device has been active. 83 For example, 84 echo $((100 * `cat active_duration` / `cat connected_duration`)) 85 will give an integer percentage. Note that this does not 86 account for counter wrap. 87Users: 88 PowerTOP <power@bughost.org> 89 http://www.lesswatts.org/projects/powertop/ 90 91What: /sys/bus/usb/device/<busnum>-<devnum>...:<config num>-<interface num>/supports_autosuspend 92Date: January 2008 93KernelVersion: 2.6.27 94Contact: Sarah Sharp <sarah.a.sharp@intel.com> 95Description: 96 When read, this file returns 1 if the interface driver 97 for this interface supports autosuspend. It also 98 returns 1 if no driver has claimed this interface, as an 99 unclaimed interface will not stop the device from being 100 autosuspended if all other interface drivers are idle. 101 The file returns 0 if autosuspend support has not been 102 added to the driver. 103Users: 104 USB PM tool 105 git://git.moblin.org/users/sarah/usb-pm-tool/ 106 107What: /sys/bus/usb/device/.../authorized 108Date: July 2008 109KernelVersion: 2.6.26 110Contact: David Vrabel <david.vrabel@csr.com> 111Description: 112 Authorized devices are available for use by device 113 drivers, non-authorized one are not. By default, wired 114 USB devices are authorized. 115 116 Certified Wireless USB devices are not authorized 117 initially and should be (by writing 1) after the 118 device has been authenticated. 119 120What: /sys/bus/usb/device/.../wusb_cdid 121Date: July 2008 122KernelVersion: 2.6.27 123Contact: David Vrabel <david.vrabel@csr.com> 124Description: 125 For Certified Wireless USB devices only. 126 127 A devices's CDID, as 16 space-separated hex octets. 128 129What: /sys/bus/usb/device/.../wusb_ck 130Date: July 2008 131KernelVersion: 2.6.27 132Contact: David Vrabel <david.vrabel@csr.com> 133Description: 134 For Certified Wireless USB devices only. 135 136 Write the device's connection key (CK) to start the 137 authentication of the device. The CK is 16 138 space-separated hex octets. 139 140What: /sys/bus/usb/device/.../wusb_disconnect 141Date: July 2008 142KernelVersion: 2.6.27 143Contact: David Vrabel <david.vrabel@csr.com> 144Description: 145 For Certified Wireless USB devices only. 146 147 Write a 1 to force the device to disconnect 148 (equivalent to unplugging a wired USB device). 149 150What: /sys/bus/usb/drivers/.../remove_id 151Date: November 2009 152Contact: CHENG Renquan <rqcheng@smu.edu.sg> 153Description: 154 Writing a device ID to this file will remove an ID 155 that was dynamically added via the new_id sysfs entry. 156 The format for the device ID is: 157 idVendor idProduct. After successfully 158 removing an ID, the driver will no longer support the 159 device. This is useful to ensure auto probing won't 160 match the driver to the device. For example: 161 # echo "046d c315" > /sys/bus/usb/drivers/foo/remove_id 162 163What: /sys/bus/usb/device/.../avoid_reset_quirk 164Date: December 2009 165Contact: Oliver Neukum <oliver@neukum.org> 166Description: 167 Writing 1 to this file tells the kernel that this 168 device will morph into another mode when it is reset. 169 Drivers will not use reset for error handling for 170 such devices. 171Users: 172 usb_modeswitch 173