File-copy from v4.4.100
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Please refer to that tree for all history prior to this point.
Change-Id: I8a9ee2aea93cd29c52c847d0ce33091a73ae6afe
diff --git a/Documentation/hwmon/acpi_power_meter b/Documentation/hwmon/acpi_power_meter
new file mode 100644
index 0000000..c80399a
--- /dev/null
+++ b/Documentation/hwmon/acpi_power_meter
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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: 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.