Documentation/ABI/stable/sysfs-bus-usb

Source file repositories/reference/linux-study-clean/Documentation/ABI/stable/sysfs-bus-usb

File Facts

System
Linux kernel
Corpus path
Documentation/ABI/stable/sysfs-bus-usb
Extension
[no extension]
Size
5067 bytes
Lines
143
Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: Documentation
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

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

Annotation

Implementation Notes