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1Kernel driver power_meter2=========================3 4This driver talks to ACPI 4.0 power meters.5 6Supported systems:7 8 * Any recent system with ACPI 4.0.9 10 Prefix: 'power_meter'11 12 Datasheet: https://uefi.org/specifications, section 10.4.13 14Author: Darrick J. Wong15 16Description17-----------18 19This driver implements sensor reading support for the power meters exposed in20the ACPI 4.0 spec (Chapter 10.4). These devices have a simple set of21features--a power meter that returns average power use over a configurable22interval, an optional capping mechanism, and a couple of trip points. The23sysfs interface conforms with the specification outlined in the "Power" section24of Documentation/hwmon/sysfs-interface.rst.25 26Special Features27----------------28 29The `power[1-*]_is_battery` knob indicates if the power supply is a battery.30Both `power[1-*]_average_{min,max}` must be set before the trip points will work.31When both of them are set, an ACPI event will be broadcast on the ACPI netlink32socket and a poll notification will be sent to the appropriate33`power[1-*]_average` sysfs file.34 35The `power[1-*]_{model_number, serial_number, oem_info}` fields display36arbitrary strings that ACPI provides with the meter. The measures/ directory37contains symlinks to the devices that this meter measures.38 39Some computers have the ability to enforce a power cap in hardware. If this is40the case, the `power[1-*]_cap` and related sysfs files will appear. When the41average power consumption exceeds the cap, an ACPI event will be broadcast on42the netlink event socket and a poll notification will be sent to the43appropriate `power[1-*]_alarm` file to indicate that capping has begun, and the44hardware has taken action to reduce power consumption. Most likely this will45result in reduced performance.46 47There are a few other ACPI notifications that can be sent by the firmware. In48all cases the ACPI event will be broadcast on the ACPI netlink event socket as49well as sent as a poll notification to a sysfs file. The events are as50follows:51 52`power[1-*]_cap` will be notified if the firmware changes the power cap.53`power[1-*]_interval` will be notified if the firmware changes the averaging54interval.55