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