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Commit 979e524a authored by Sarah Sharp's avatar Sarah Sharp Committed by Greg Kroah-Hartman
Browse files

USB: Add documentation for USB suspend statistics. 



This documents two newly created files:
/sys/bus/usb/device/.../power/connected_duration
/sys/bus/usb/device/.../power/active_duration

Documentation was placed in Documentation/ABI/testing, since that's where the
documentation is for the other USB sysfs power files.

Signed-off-by: default avatarSarah Sharp <sarah.a.sharp@intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 15123006

Documentation/ABI/testing/sysfs-bus-usb

+33 −0
Original line number Diff line number Diff line
@@ -52,3 +52,36 @@ Description: 
		facility is inherently dangerous, it is disabled by default

		for all devices except hubs.  For more information, see

		Documentation/usb/persist.txt.



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 and CONFIG_USB_SUSPEND are 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 <power@bughost.org>

		http://www.lesswatts.org/projects/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 and CONFIG_USB_SUSPEND are 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 <power@bughost.org>

		http://www.lesswatts.org/projects/powertop/