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- What: /sys/bus/usb/devices/.../power/persist
- Date: May 2007
- KernelVersion: 2.6.23
- Contact: Alan Stern <stern@rowland.harvard.edu>
- Description:
- USB device directories can contain a file named power/persist.
- The file holds a boolean value (0 or 1) indicating whether or
- not the "USB-Persist" facility is enabled for the device. For
- hubs this facility is always enabled and their device
- directories will not contain this file.
- For more information, see Documentation/usb/persist.txt.
- What: /sys/bus/usb/devices/.../power/autosuspend
- Date: March 2007
- KernelVersion: 2.6.21
- Contact: Alan Stern <stern@rowland.harvard.edu>
- Description:
- Each USB device directory will contain a file named
- power/autosuspend. This file holds the time (in seconds)
- the device must be idle before it will be autosuspended.
- 0 means the device will be autosuspended as soon as
- possible. Negative values will prevent the device from
- being autosuspended at all, and writing a negative value
- will resume the device if it is already suspended.
- The autosuspend delay for newly-created devices is set to
- the value of the usbcore.autosuspend module parameter.
- What: /sys/bus/usb/device/.../power/connected_duration
- Date: January 2008
- KernelVersion: 2.6.25
- Contact: Sarah Sharp <sarah.a.sharp@intel.com>
- Description:
- If CONFIG_PM_RUNTIME is enabled then this file
- is present. When read, it returns the total time (in msec)
- that the USB device has been connected to the machine. This
- file is read-only.
- Users:
- PowerTOP <powertop@lists.01.org>
- https://01.org/powertop/
- What: /sys/bus/usb/device/.../power/active_duration
- Date: January 2008
- KernelVersion: 2.6.25
- Contact: Sarah Sharp <sarah.a.sharp@intel.com>
- Description:
- If CONFIG_PM_RUNTIME is enabled then this file
- is present. When read, it returns the total time (in msec)
- that the USB device has been active, i.e. not in a suspended
- state. This file is read-only.
- Tools can use this file and the connected_duration file to
- compute the percentage of time that a device has been active.
- For example,
- echo $((100 * `cat active_duration` / `cat connected_duration`))
- will give an integer percentage. Note that this does not
- account for counter wrap.
- Users:
- PowerTOP <powertop@lists.01.org>
- https://01.org/powertop/
- What: /sys/bus/usb/devices/<busnum>-<port[.port]>...:<config num>-<interface num>/supports_autosuspend
- Date: January 2008
- KernelVersion: 2.6.27
- Contact: Sarah Sharp <sarah.a.sharp@intel.com>
- Description:
- When read, this file returns 1 if the interface driver
- for this interface supports autosuspend. It also
- returns 1 if no driver has claimed this interface, as an
- unclaimed interface will not stop the device from being
- autosuspended if all other interface drivers are idle.
- The file returns 0 if autosuspend support has not been
- added to the driver.
- Users:
- USB PM tool
- git://git.moblin.org/users/sarah/usb-pm-tool/
- What: /sys/bus/usb/device/.../avoid_reset_quirk
- Date: December 2009
- Contact: Oliver Neukum <oliver@neukum.org>
- Description:
- Writing 1 to this file tells the kernel that this
- device will morph into another mode when it is reset.
- Drivers will not use reset for error handling for
- such devices.
- Users:
- usb_modeswitch
- What: /sys/bus/usb/devices/.../devnum
- KernelVersion: since at least 2.6.18
- Description:
- Device address on the USB bus.
- Users:
- libusb
- What: /sys/bus/usb/devices/.../bConfigurationValue
- KernelVersion: since at least 2.6.18
- Description:
- bConfigurationValue of the *active* configuration for the
- device. Writing 0 or -1 to bConfigurationValue will reset the
- active configuration (unconfigure the device). Writing
- another value will change the active configuration.
- Note that some devices, in violation of the USB spec, have a
- configuration with a value equal to 0. Writing 0 to
- bConfigurationValue for these devices will install that
- configuration, rather then unconfigure the device.
- Writing -1 will always unconfigure the device.
- Users:
- libusb
- What: /sys/bus/usb/devices/.../busnum
- KernelVersion: 2.6.22
- Description:
- Bus-number of the USB-bus the device is connected to.
- Users:
- libusb
- What: /sys/bus/usb/devices/.../descriptors
- KernelVersion: 2.6.26
- Description:
- Binary file containing cached descriptors of the device. The
- binary data consists of the device descriptor followed by the
- descriptors for each configuration of the device.
- Note that the wTotalLength of the config descriptors can not
- be trusted, as the device may have a smaller config descriptor
- than it advertises. The bLength field of each (sub) descriptor
- can be trusted, and can be used to seek forward one (sub)
- descriptor at a time until the next config descriptor is found.
- All descriptors read from this file are in bus-endian format
- Users:
- libusb
- What: /sys/bus/usb/devices/.../speed
- KernelVersion: since at least 2.6.18
- Description:
- Speed the device is connected with to the usb-host in
- Mbit / second. IE one of 1.5 / 12 / 480 / 5000.
- Users:
- libusb
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