About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / hwmon / acpi_power_meter




Custom Search

Based on kernel version 3.15.4. Page generated on 2014-07-07 09:03 EST.

1	Kernel driver power_meter
2	=========================
3	
4	This driver talks to ACPI 4.0 power meters.
5	
6	Supported systems:
7	  * Any recent system with ACPI 4.0.
8	    Prefix: 'power_meter'
9	    Datasheet: http://acpi.info/, section 10.4.
10	
11	Author: Darrick J. Wong
12	
13	Description
14	-----------
15	
16	This driver implements sensor reading support for the power meters exposed in
17	the ACPI 4.0 spec (Chapter 10.4).  These devices have a simple set of
18	features--a power meter that returns average power use over a configurable
19	interval, an optional capping mechanism, and a couple of trip points.  The
20	sysfs interface conforms with the specification outlined in the "Power" section
21	of Documentation/hwmon/sysfs-interface.
22	
23	Special Features
24	----------------
25	
26	The power[1-*]_is_battery knob indicates if the power supply is a battery.
27	Both power[1-*]_average_{min,max} must be set before the trip points will work.
28	When both of them are set, an ACPI event will be broadcast on the ACPI netlink
29	socket and a poll notification will be sent to the appropriate
30	power[1-*]_average sysfs file.
31	
32	The power[1-*]_{model_number, serial_number, oem_info} fields display arbitrary
33	strings that ACPI provides with the meter.  The measures/ directory contains
34	symlinks to the devices that this meter measures.
35	
36	Some computers have the ability to enforce a power cap in hardware.  If this is
37	the case, the power[1-*]_cap and related sysfs files will appear.  When the
38	average power consumption exceeds the cap, an ACPI event will be broadcast on
39	the netlink event socket and a poll notification will be sent to the
40	appropriate power[1-*]_alarm file to indicate that capping has begun, and the
41	hardware has taken action to reduce power consumption.  Most likely this will
42	result in reduced performance.
43	
44	There are a few other ACPI notifications that can be sent by the firmware.  In
45	all cases the ACPI event will be broadcast on the ACPI netlink event socket as
46	well as sent as a poll notification to a sysfs file.  The events are as
47	follows:
48	
49	power[1-*]_cap will be notified if the firmware changes the power cap.
50	power[1-*]_interval will be notified if the firmware changes the averaging
51	interval.
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.