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- 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: https://uefi.org/specifications, 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.rst.
- 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.
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