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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: Sarah Sharp <sarah.a.sharp@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Sarah Sharp 2008-01-17 10:24:38 -08:00 committed by Greg Kroah-Hartman
parent 1512300689
commit 979e524a9c
1 changed files with 33 additions and 0 deletions
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33
Documentation/ABI/testing/sysfs-bus-usb
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@ -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/