Documentation/hwmon/acpi_power_meter.rst
This driver talks to ACPI 4.0 power meters.
Supported systems:
Any recent system with ACPI 4.0.
Prefix: 'power_meter'
Datasheet: https://uefi.org/specifications, section 10.4.
Author: Darrick J. Wong
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.rst.
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.
For information on enabling the power cap feature, refer to the description
of the "force_on_cap" option in the "Module Parameters" chapter.
To use the power cap feature properly, you need to set appropriate value
(in microWatts) to the power[1-*]_cap sysfs files.
The value must be within the range between the minimum value at power[1-]_cap_min
and the maximum value at power[1-]_cap_max (both in microWatts).
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.
force_cap_on: bool Forcefully enable the power capping feature to specify the upper limit of the system's power consumption.
By default, the driver's power capping feature is only
enabled on IBM products.
Therefore, on other systems that support power capping,
you will need to use the option to enable it.
Note: power capping is potentially unsafe feature.
Please check the platform specifications to make sure
that capping is supported before using this option.