mirror of
https://github.com/torvalds/linux.git
synced 2024-11-18 01:51:53 +00:00
52 lines
2.1 KiB
Plaintext
52 lines
2.1 KiB
Plaintext
|
Kernel driver power_meter
|
||
|
|
=========================
|
||
|
|
|
||
|
|
This driver talks to ACPI 4.0 power meters.
|
||
|
|
|
||
|
|
Supported systems:
|
||
|
|
* Any recent system with ACPI 4.0.
|
||
|
|
Prefix: 'power_meter'
|
||
|
|
Datasheet: http://acpi.info/, section 10.4.
|
||
|
|
|
||
|
|
Author: Darrick J. Wong
|
||
|
|
|
||
|
|
Description
|
||
|
|
-----------
|
||
|
|
|
||
|
|
This driver implements sensor reading support for the power meters exposed in
|
||
|
|
the ACPI 4.0 spec (Chapter 10.4). These devices have a simple set of
|
||
|
|
features--a power meter that returns average power use over a configurable
|
||
|
|
interval, an optional capping mechanism, and a couple of trip points. The
|
||
|
|
sysfs interface conforms with the specification outlined in the "Power" section
|
||
|
|
of Documentation/hwmon/sysfs-interface.
|
||
|
|
|
||
|
|
Special Features
|
||
|
|
----------------
|
||
|
|
|
||
|
|
The power[1-*]_is_battery knob indicates if the power supply is a battery.
|
||
|
|
Both power[1-*]_average_{min,max} must be set before the trip points will work.
|
||
|
|
When both of them are set, an ACPI event will be broadcast on the ACPI netlink
|
||
|
|
socket and a poll notification will be sent to the appropriate
|
||
|
|
power[1-*]_average sysfs file.
|
||
|
|
|
||
|
|
The power[1-*]_{model_number, serial_number, oem_info} fields display arbitrary
|
||
|
|
strings that ACPI provides with the meter. The measures/ directory contains
|
||
|
|
symlinks to the devices that this meter measures.
|
||
|
|
|
||
|
|
Some computers have the ability to enforce a power cap in hardware. If this is
|
||
|
|
the case, the power[1-*]_cap and related sysfs files will appear. When the
|
||
|
|
average power consumption exceeds the cap, an ACPI event will be broadcast on
|
||
|
|
the netlink event socket and a poll notification will be sent to the
|
||
|
|
appropriate power[1-*]_alarm file to indicate that capping has begun, and the
|
||
|
|
hardware has taken action to reduce power consumption. Most likely this will
|
||
|
|
result in reduced performance.
|
||
|
|
|
||
|
|
There are a few other ACPI notifications that can be sent by the firmware. In
|
||
|
|
all cases the ACPI event will be broadcast on the ACPI netlink event socket as
|
||
|
|
well as sent as a poll notification to a sysfs file. The events are as
|
||
|
|
follows:
|
||
|
|
|
||
|
|
power[1-*]_cap will be notified if the firmware changes the power cap.
|
||
|
|
power[1-*]_interval will be notified if the firmware changes the averaging
|
||
|
|
interval.
|