Documentation/ABI/testing/sysfs-bus-usb

   1 What:           /sys/bus/usb/devices/.../power/autosuspend
   2 Date:           March 2007
   3 KernelVersion:  2.6.21
   4 Contact:        Alan Stern <stern@rowland.harvard.edu>
   5 Description:
   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
  17 What:           /sys/bus/usb/devices/.../power/level
  18 Date:           March 2007
  19 KernelVersion:  2.6.21
  20 Contact:        Alan Stern <stern@rowland.harvard.edu>
  21 Description:
  22                 Each USB device directory will contain a file named
  23                 power/level.  This file holds a power-level setting for
  24                 the device, one of "on", "auto", or "suspend".
  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.  "suspend" means the device
  31                 is forced into a suspended state and it will not autoresume
  32                 in response to I/O requests.  However remote-wakeup requests
  33                 from the device may still be enabled (the remote-wakeup
  34                 setting is controlled separately by the power/wakeup
  35                 attribute).
  36
  37                 During normal use, devices should be left in the "auto"
  38                 level.  The other levels are meant for administrative uses.
  39                 If you want to suspend a device immediately but leave it
  40                 free to wake up in response to I/O requests, you should
  41                 write "0" to power/autosuspend.
  42
  43 What:           /sys/bus/usb/devices/.../power/persist
  44 Date:           May 2007
  45 KernelVersion:  2.6.23
  46 Contact:        Alan Stern <stern@rowland.harvard.edu>
  47 Description:
  48                 If CONFIG_USB_PERSIST is set, then each USB device directory
  49                 will contain a file named power/persist.  The file holds a
  50                 boolean value (0 or 1) indicating whether or not the
  51                 "USB-Persist" facility is enabled for the device.  Since the
  52                 facility is inherently dangerous, it is disabled by default
  53                 for all devices except hubs.  For more information, see
  54                 Documentation/usb/persist.txt.
  55
  56 What:           /sys/bus/usb/device/.../power/connected_duration
  57 Date:           January 2008
  58 KernelVersion:  2.6.25
  59 Contact:        Sarah Sharp <sarah.a.sharp@intel.com>
  60 Description:
  61                 If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file
  62                 is present.  When read, it returns the total time (in msec)
  63                 that the USB device has been connected to the machine.  This
  64                 file is read-only.
  65 Users:
  66                 PowerTOP <power@bughost.org>
  67                 http://www.lesswatts.org/projects/powertop/
  68
  69 What:           /sys/bus/usb/device/.../power/active_duration
  70 Date:           January 2008
  71 KernelVersion:  2.6.25
  72 Contact:        Sarah Sharp <sarah.a.sharp@intel.com>
  73 Description:
  74                 If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file
  75                 is present.  When read, it returns the total time (in msec)
  76                 that the USB device has been active, i.e. not in a suspended
  77                 state.  This file is read-only.
  78
  79                 Tools can use this file and the connected_duration file to
  80                 compute the percentage of time that a device has been active.
  81                 For example,
  82                 echo $((100 * `cat active_duration` / `cat connected_duration`))
  83                 will give an integer percentage.  Note that this does not
  84                 account for counter wrap.
  85 Users:
  86                 PowerTOP <power@bughost.org>
  87                 http://www.lesswatts.org/projects/powertop/
  88
  89 What:           /sys/bus/usb/device/<busnum>-<devnum>...:<config num>-<interface num>/supports_autosuspend
  90 Date:           January 2008
  91 KernelVersion:  2.6.27
  92 Contact:        Sarah Sharp <sarah.a.sharp@intel.com>
  93 Description:
  94                 When read, this file returns 1 if the interface driver
  95                 for this interface supports autosuspend.  It also
  96                 returns 1 if no driver has claimed this interface, as an
  97                 unclaimed interface will not stop the device from being
  98                 autosuspended if all other interface drivers are idle.
  99                 The file returns 0 if autosuspend support has not been
 100                 added to the driver.
 101 Users:
 102                 USB PM tool
 103                 git://git.moblin.org/users/sarah/usb-pm-tool/
 104
 105 What:           /sys/bus/usb/device/.../authorized
 106 Date:           July 2008
 107 KernelVersion:  2.6.26
 108 Contact:        David Vrabel <david.vrabel@csr.com>
 109 Description:
 110                 Authorized devices are available for use by device
 111                 drivers, non-authorized one are not.  By default, wired
 112                 USB devices are authorized.
 113
 114                 Certified Wireless USB devices are not authorized
 115                 initially and should be (by writing 1) after the
 116                 device has been authenticated.
 117
 118 What:           /sys/bus/usb/device/.../wusb_cdid
 119 Date:           July 2008
 120 KernelVersion:  2.6.27
 121 Contact:        David Vrabel <david.vrabel@csr.com>
 122 Description:
 123                 For Certified Wireless USB devices only.
 124
 125                 A devices's CDID, as 16 space-separated hex octets.
 126
 127 What:           /sys/bus/usb/device/.../wusb_ck
 128 Date:           July 2008
 129 KernelVersion:  2.6.27
 130 Contact:        David Vrabel <david.vrabel@csr.com>
 131 Description:
 132                 For Certified Wireless USB devices only.
 133
 134                 Write the device's connection key (CK) to start the
 135                 authentication of the device.  The CK is 16
 136                 space-separated hex octets.
 137
 138 What:           /sys/bus/usb/device/.../wusb_disconnect
 139 Date:           July 2008
 140 KernelVersion:  2.6.27
 141 Contact:        David Vrabel <david.vrabel@csr.com>
 142 Description:
 143                 For Certified Wireless USB devices only.
 144
 145                 Write a 1 to force the device to disconnect
 146                 (equivalent to unplugging a wired USB device).