Darrick J. Wong | de584af | 2009-09-18 12:41:09 -0700 | [diff] [blame] | 1 | Kernel driver power_meter |
| 2 | ========================= |
| 3 | |
| 4 | This driver talks to ACPI 4.0 power meters. |
| 5 | |
| 6 | Supported systems: |
Mauro Carvalho Chehab | b04f2f7 | 2019-04-17 06:46:28 -0300 | [diff] [blame] | 7 | |
Darrick J. Wong | de584af | 2009-09-18 12:41:09 -0700 | [diff] [blame] | 8 | * Any recent system with ACPI 4.0. |
Mauro Carvalho Chehab | b04f2f7 | 2019-04-17 06:46:28 -0300 | [diff] [blame] | 9 | |
Darrick J. Wong | de584af | 2009-09-18 12:41:09 -0700 | [diff] [blame] | 10 | Prefix: 'power_meter' |
Mauro Carvalho Chehab | b04f2f7 | 2019-04-17 06:46:28 -0300 | [diff] [blame] | 11 | |
Darrick J. Wong | de584af | 2009-09-18 12:41:09 -0700 | [diff] [blame] | 12 | Datasheet: http://acpi.info/, section 10.4. |
| 13 | |
| 14 | Author: Darrick J. Wong |
| 15 | |
| 16 | Description |
| 17 | ----------- |
| 18 | |
| 19 | This driver implements sensor reading support for the power meters exposed in |
| 20 | the ACPI 4.0 spec (Chapter 10.4). These devices have a simple set of |
| 21 | features--a power meter that returns average power use over a configurable |
| 22 | interval, an optional capping mechanism, and a couple of trip points. The |
| 23 | sysfs interface conforms with the specification outlined in the "Power" section |
Mauro Carvalho Chehab | 7ebd8b66 | 2019-04-17 06:46:29 -0300 | [diff] [blame] | 24 | of Documentation/hwmon/sysfs-interface.rst. |
Darrick J. Wong | de584af | 2009-09-18 12:41:09 -0700 | [diff] [blame] | 25 | |
| 26 | Special Features |
| 27 | ---------------- |
| 28 | |
Mauro Carvalho Chehab | b04f2f7 | 2019-04-17 06:46:28 -0300 | [diff] [blame] | 29 | The `power[1-*]_is_battery` knob indicates if the power supply is a battery. |
| 30 | Both `power[1-*]_average_{min,max}` must be set before the trip points will work. |
Darrick J. Wong | de584af | 2009-09-18 12:41:09 -0700 | [diff] [blame] | 31 | When both of them are set, an ACPI event will be broadcast on the ACPI netlink |
| 32 | socket and a poll notification will be sent to the appropriate |
Mauro Carvalho Chehab | b04f2f7 | 2019-04-17 06:46:28 -0300 | [diff] [blame] | 33 | `power[1-*]_average` sysfs file. |
Darrick J. Wong | de584af | 2009-09-18 12:41:09 -0700 | [diff] [blame] | 34 | |
Mauro Carvalho Chehab | b04f2f7 | 2019-04-17 06:46:28 -0300 | [diff] [blame] | 35 | The `power[1-*]_{model_number, serial_number, oem_info}` fields display |
| 36 | arbitrary strings that ACPI provides with the meter. The measures/ directory |
| 37 | contains symlinks to the devices that this meter measures. |
Darrick J. Wong | de584af | 2009-09-18 12:41:09 -0700 | [diff] [blame] | 38 | |
| 39 | Some computers have the ability to enforce a power cap in hardware. If this is |
Mauro Carvalho Chehab | b04f2f7 | 2019-04-17 06:46:28 -0300 | [diff] [blame] | 40 | the case, the `power[1-*]_cap` and related sysfs files will appear. When the |
Darrick J. Wong | de584af | 2009-09-18 12:41:09 -0700 | [diff] [blame] | 41 | average power consumption exceeds the cap, an ACPI event will be broadcast on |
| 42 | the netlink event socket and a poll notification will be sent to the |
Mauro Carvalho Chehab | b04f2f7 | 2019-04-17 06:46:28 -0300 | [diff] [blame] | 43 | appropriate `power[1-*]_alarm` file to indicate that capping has begun, and the |
Darrick J. Wong | de584af | 2009-09-18 12:41:09 -0700 | [diff] [blame] | 44 | hardware has taken action to reduce power consumption. Most likely this will |
| 45 | result in reduced performance. |
| 46 | |
| 47 | There are a few other ACPI notifications that can be sent by the firmware. In |
| 48 | all cases the ACPI event will be broadcast on the ACPI netlink event socket as |
| 49 | well as sent as a poll notification to a sysfs file. The events are as |
| 50 | follows: |
| 51 | |
Mauro Carvalho Chehab | b04f2f7 | 2019-04-17 06:46:28 -0300 | [diff] [blame] | 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 averaging |
Darrick J. Wong | de584af | 2009-09-18 12:41:09 -0700 | [diff] [blame] | 54 | interval. |