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authorSarah Sharp <sarah.a.sharp@intel.com>2008-01-17 13:24:38 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2008-02-01 17:35:00 -0500
commit979e524a9c563376af096d2d8629b9969fc06659 (patch)
tree3401e794419fd257a2ed045b085e79f15b9d590e /Documentation
parent1512300689426cb98bfd7e567ee9fdfaaf61b7c7 (diff)
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>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/ABI/testing/sysfs-bus-usb33
1 files changed, 33 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb
index 9734577d1711..11a3c1682cec 100644
--- a/Documentation/ABI/testing/sysfs-bus-usb
+++ b/Documentation/ABI/testing/sysfs-bus-usb
@@ -52,3 +52,36 @@ Description:
52 facility is inherently dangerous, it is disabled by default 52 facility is inherently dangerous, it is disabled by default
53 for all devices except hubs. For more information, see 53 for all devices except hubs. For more information, see
54 Documentation/usb/persist.txt. 54 Documentation/usb/persist.txt.
55
56What: /sys/bus/usb/device/.../power/connected_duration
57Date: January 2008
58KernelVersion: 2.6.25
59Contact: Sarah Sharp <sarah.a.sharp@intel.com>
60Description:
61 If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file
62 is present. When read, it returns the total time (in msec)
63 that the USB device has been connected to the machine. This
64 file is read-only.
65Users:
66 PowerTOP <power@bughost.org>
67 http://www.lesswatts.org/projects/powertop/
68
69What: /sys/bus/usb/device/.../power/active_duration
70Date: January 2008
71KernelVersion: 2.6.25
72Contact: Sarah Sharp <sarah.a.sharp@intel.com>
73Description:
74 If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file
75 is present. When read, it returns the total time (in msec)
76 that the USB device has been active, i.e. not in a suspended
77 state. This file is read-only.
78
79 Tools can use this file and the connected_duration file to
80 compute the percentage of time that a device has been active.
81 For example,
82 echo $((100 * `cat active_duration` / `cat connected_duration`))
83 will give an integer percentage. Note that this does not
84 account for counter wrap.
85Users:
86 PowerTOP <power@bughost.org>
87 http://www.lesswatts.org/projects/powertop/