torvalds/linux

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/driver-api/usb/persist.rst.

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 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 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