docs/control/events.md

# events.json

This file defines the events that dictate how fan control operates.  Each event
can contain groups, triggers, and actions.

Actions are where fan targets are calculated and set, among other things.
Triggers specify when an action should run. Groups specify which D-Bus objects
the triggers and actions should operate on.

Some actions have modifiers, which help calculate a value.

- [Groups](#groups)
- [Triggers](#triggers)
- [Actions](#actions)
- [Modifiers](#modifiers)

## Example

```
[
   {
     "name": "fan(s) missing",
     "groups": [
       {
         "name": "fan inventory",
         "interface": "xyz.openbmc_project.Inventory.Item",
         "property": { "name": "Present" }
       }
     ],
     "triggers": [
       {
         "class": "init",
         "method": "get_properties"
       },
       {
         "class": "signal",
         "signal": "properties_changed"
       }
     ],
     "actions": [
       {
         "name": "count_state_before_target",
         "count": 1,
         "state": false,
         "target": 15000
       }
     ]
   }
]
```

The above event is an example of a method to set the fan target to 15000 when
one or more fans is missing. The basic behavior with this config is:

The trigger `init.get_properties` will, on fan control startup, read the
Present property on the `xyz.openbmc_project.Inventory.Item` interface from
every D-Bus object in the 'fan inventory' group, update those values in the
object cache, and then call the `count_state_before_target` action.

The trigger `signal.properties_changed` will watch for changes on the Present
property on each D-Bus object in the group, update the new value in the object
cache, and call the `count_state_before_target` action when the value changes.

The `count_state_before_target` action will look at the object cache value of
the Present property on each member of the group and set the fan target hold to
15000 when one or more of them is false.  Otherwise, it will clear its fan
target hold.

## Groups

```
"groups": [
    {
        "name": "<name>",
        "interface": "<interface>",
        "property": { "name": "<name>" }
    }
    ...
]
```

### name
The name of a group that must be also be defined in
[groups.json](groups.md).

### interface
The actions and triggers defined with this group will look at this D-Bus
interface on the members of this group.

### property: name
The actions and triggers defined with this group will look at this D-Bus
property on the members of this group.

## Triggers

There are several classes of triggers, and the JSON configuration is different
for each.

### init
Init triggers run when fan control events are enabled on fan control startup.
After invoking the configured method, any actions configured for this trigger
will run.

```
{
    "class": "init",
    "method": "<method>"
}
```

#### methods

1. `get_properties` - Read the property configured for the group from every
   member of the group, and store it in fan control's object cache.

2. `name_has_owner` - Populates the service owned state from D-Bus for each
   group member in fan control's D-Bus service cache map.

### signal
Signal triggers subscribe to certain D-Bus signals for each member of its
configured group.  After handling the signal, any configured actions are run.

```
{
    "class": "signal",
    "signal": "<signal>"
}
```

#### signal types
1. `properties_changed` - Subscribes to the PropertiesChanged signal for the
   D-Bus interface and property specified in the group definition for each
   group member.  When the signal occurs, the new property value will be added
   to or updated in the object cache.

2. `interfaces_added` - Subscribes to the InterfacesAdded signal for the D-Bus
   interface specified in the group definition for each group member.  When the
   signal occurs, the interface and its properties will be added to the object
   cache.

3. `interfaces_removed` - Subscribes to the InterfacesRemoved signal for the
   D-Bus interface specified in the group definition for each group member.
   When the signal occurs, the interface and properties will be removed from
   the object cache.

4. `name_owner_changed` - Subscribes to the NameOwnerChanged signal for the
   services that host the D-bus interface specified in the group definition for
   each group member.  When the signal occurs, the service owned state will be
   updated in the service cache map.

5. `member` - Subscribes to the signal listed on each group member.  No caches
   are updated when the signal occurs.

### timer
Timer triggers run actions after the configured type of timer expires.

```
{
    "class": "timer",
    "type": "<type>",
    "interval": "<interval>",
    "preload_groups": "<true/false>"
}
```

#### type
1. `oneshot` - Starts a timer that runs once.

2. `repeating` - Starts a repeating timer.

#### interval
The timer length in microseconds

#### preload_groups
Optional, if set to true, will update the D-Bus properties from the configured
groups in the object cache after the timer expires but before any actions run.

### parameter
Parameter triggers run actions after a parameter changes.

```
{
    "class": "parameter",
    "parameter": "<parameter>"
}
```
#### parameter
The parameter value to watch.

### poweron
PowerOn triggers run when the power turns on.  Functionally, they behave like
an init trigger.

```
{
    "class": "poweron",
    "method": "<method>"
}
```

#### method
The methods are the same as with the init trigger.

### poweroff

PowerOff triggers run when the power turns off.  Functionally, they behave like
an init trigger.

```
{
    "class": "poweroff",
    "method": "<method>"
}
```

#### method
The methods are the same as with the init trigger.

## Actions
Actions can either operate on the groups listed with the event, or on the
groups listed within the action's JSON config.

Most actions set fan targets or floors.  This can be done by requesting a
target value explicitly, or by requesting an increase or decrease delta.
Targets and floors can also be set with a hold, meaning another action can't
set a floor/target below the one that is held.

Some actions set or read a key/value pair called a parameter.  These can be
created, updated, and deleted as necessary.  For example, one action may
calculate and set a `floor_index` parameter, and another action may then read
that parameter to help choose a fan floor.

The available actions are:

- [set_net_increase_target](#set_net_increase_target)
- [set_net_decrease_target](#set_net_decrease_target)
- [count_state_floor](#count_state_floor)
- [count_state_before_target](#count_state_before_target)
- [default_floor_on_missing_owner](#default_floor_on_missing_owner)
- [mapped_floor](#mapped_floor)
- [set_target_on_missing_owner](#set_target_on_missing_owner)
- [override_fan_target](#override_fan_target)
- [pcie_card_floors](#pcie_card_floors)
- [set_request_target_base_with_max](#set_request_target_base_with_max)
- [set_parameter_from_group_max](#set_parameter_from_group_max)
- [target_from_group_max](#target_from_group_max)
- [call_actions_based_on_timer](#call_actions_based_on_timer)
- [get_managed_objects](#get_managed_objects)

### set_net_increase_target

Calculates the net target increase to be requested based on the value of each
property given within a group. The net target increase is based on the maximum
difference between the `delta` JSON value and all of the properties of the group.
The final result is the increase change that's requested to the current target
of a zone.

The group values can be compared to either a value hardcoded in the JSON, or a
parameter value.

```
{
    "name": "set_net_increase_target",
    "groups": [{
        "name": "pcie temps",
        "interface": "xyz.openbmc_project.Sensor.Value",
        "property": { "name": "Value" }
      }],
    "state": 70.0,
    "delta": 255
}
```

The above config uses a hardcoded state value:
1. For each member of the 'pcie temps' group:
  - Read its 'Value' D-Bus property.
  - If that property value is greater than the 'state' value of 70.0:
   - Subtracts 70.0 from the property value.
   - Multiplies that difference by the 'delta' value of 255.
2. Requests an increase of the largest calculated delta value, if there is
   one.

```
{
    "name": "set_net_increase_target",
    "groups": [{
        "name": "proc0 core temps",
        "interface": "xyz.openbmc_project.Sensor.Value",
        "property": { "name": "Value" }
      }],
    "state_parameter_name": "proc_0_core_dvfs_increase_temp",
    "delta": 300
}
```

The above config uses a parameter as the state value:
1. For each member of the 'proc 0 core temps' group:
  - Read its 'Value' D-Bus property.
  - If that property value is greater than the value of the parameter listed in
    the 'state_parameter_name' field, in this case
    'proc_0_core_dvfs_increase_temp':
   - Subtracts that parameter value from the property value.
   - Multiplies that difference by the 'delta' value of 300.
2. Requests an increase of the largest calculated delta value, if there is one.

### set_net_decrease_target
Calculates the net target decrease to be requested based on the value of each
property given within a group. The net target decrease is based on the minimum
difference between the `delta` JSON value and all properties in the group. The
final result is the decrease change that's requested to the current target of a
zone.

The group values can be compared to either a value hardcoded in the JSON, or a
parameter value.

```
{
    "name": "set_net_decrease_target",
    "groups": [{
        "name": "pcie temps",
        "interface": "xyz.openbmc_project.Sensor.Value",
        "property": { "name": "Value" }
      }],
    "state": 65.0,
    "delta": 80
}

```

The above config uses a hardcoded state value:
1. For each member of the 'pcie temps' group:
  - Read its 'Value' D-Bus property.
  - If that property value is less than the 'state' value of 65.0:
   - Subtracts the property value from 65.0.
   - Multiplies that difference by the 'delta' value of 80.
2. Requests a decrease of the smallest calculated delta value, if there is
   one.

```
{
    "name": "set_net_decrease_target",
    "groups": [{
        "name": "proc 0 core temps",
        "interface": "xyz.openbmc_project.Sensor.Value",
        "property": { "name": "Value" }
      }],
    "state_parameter_name": "proc_0_core_dvfs_decrease_temp",
    "delta": 50
}
```

The above config uses a parameter as the state value:
1. For each member of the 'proc 0 core temps' group:
  - Read its 'Value' D-Bus property.
  - If that property value is less than the value of the parameter listed
    the 'state_parameter_name' field, in this case
    'proc_0_core_dvfs_decrease_temp':
   - Subtracts the property value from the parameter value.
   - Multiplies that difference by the 'delta' value of 50.
2. Requests a decrease of the smallest calculated delta value, if there is
   one.

### count_state_floor
 Sets the fans to a configured floor when a number of members within the
 group are at a configured state. Once the number of members at the given
 state falls below the configured count, the floor hold is released.

```
{
    "name": "count_state_floor",
    "count": 2,
    "state": false,
    "floor": 18000
}
```

The above config reads the configured D-Bus property on each group member
configured for the action.  If two or more members have a property value of
false, a floor hold will be requested with a value of 18000.  Otherwise, the
floor hold will be released (if it was previously requested).

### count_state_before_target
Sets the fans to a configured target when a number of members within the group
are at a configured state. Once the number of members at the given state falls
below the configured count, active fan target changes are allowed.

```
{
    "name": "count_state_before_target",
    "count": 1,
    "state": false,
    "target": 18000
}
```

The above config reads the configured D-Bus property on each group member
configured for the action.  If one or more members have a property value of
false, a target hold will be requested with a value of 18000.  Otherwise, the
hold will be released (if it was previously requested).

### default_floor_on_missing_owner
Sets the fan floor to the defined zone's default fan floor when a service
associated to a given group has terminated. Once all services are functional
and providing the sensors, the fan floor is allowed to be set normally again.

There is no additional JSON config for this action.

### mapped_floor
This action can be used to set a floor value based on 2 or more groups
having values within certain ranges, where the key group chooses the set
of tables in which to check the remaining group values.

```
{
  "name": "mapped_floor",
  "key_group": "ambient temp",
  "default_floor": 5555,
  "fan_floors": [
   {
     "key": 25,
     "default_floor": 4444,
     "floor_offset_parameter": "ambient_25_altitude_offset",
     "floors": [
       {
         "parameter": "pcie_floor_index",
         "floors": [
           { "value": 1, "floor": 2000 },
           { "value": 2, "floor": 3000 },
           { "value": 3, "floor": 4000 },
           { "value": 4, "floor": 5000 },
           { "value": 5, "floor": 6000 }
         ]
       },
       {
         "group": "power save",
         "floors": [
            { "value": true, "floor": 1000 }
         ]
       }
     ]
   }
}
```

The above config will use the maximum value of the 'ambient temp' group as the
key into the 'fan_floors' tables.  There is one of those tables listed, and it
will be used when the key group has a max value of less than 25.

It will then traverse the contained floors arrays, keeping track of the highest
valid floor value it finds.  If it doesn't find any valid floor values, it will
use the `default_floor` value of 4444, though that value is optional.

If no valid tables were found given the key value, the `default_floor` value of
5555 would be used, though that is optional and if not supplied the code would
default to the default floor of the zone.

At the end of the analysis, a floor hold will be set with the final floor
value.

### set_target_on_missing_owner
Sets the fans to a configured target when any service owner associated to the
group is missing. Once all services are functional and providing all the
group data again, active fan target changes are allowed.

```
{
    "name": "set_target_on_missing_owner",
    "groups": [{
        "name": "fan inventory",
        "interface": "xyz.openbmc_project.Inventory.Item",
        "property": { "name": "Present" }
      }],
    "target": 18000
}
```

The above config will set a target hold of 18000 when the service associated
with the 'fan inventory' group is lost.

### override_fan_target
This action locks fans at configured targets when the configured `count` amount
of fans meet criterion for the particular condition. A locked fan maintains its
override target until unlocked (or locked at a higher target). Upon unlocking,
it will either revert to temperature control or activate the next-highest
target remaining in its list of locks.

```
{
    "name": "override_fan_target",
    "count": 1,
    "state": false,
    "fans": [ "fan0", "fan1", "fan2", "fan3" ],
    "target": 10000
}
```

The above config will lock all fans in the fans array at a target of 10000 when
one or more members in its configured group have a group property value of
false.

This could be used for example, to lock the rotors of a multirotor fan to a
high target when one of its rotors has a functional property equal to false.

### pcie_card_floors
Sets the `pcie_floor_index` parameter based on the current configuration of
plugged and powered on PCIe cards, using data from the `pcie_cards.json` file.

It chooses the highest index from the active PCIe cards to set in the
parameter.

It must be configured with the following groups and properties:
- The PCIe slots with the PowerState property
- The PCIe cards with the following properties: Function0DeviceId,
  Function0VendorId, Function0SubsystemId, Function0SubsystemVendorId

```
{
    "name": "pcie_card_floors",
    "use_config_specific_files": true,
    "settle_time": 2
}
```

The `use_config_specific_files` field tells the code to look for the
'pcie_cards.json' files in the same system specific directories as
'events.json'.  If missing or false, looks in the base fan control directory.

The `settle_time` field is the amount of time in seconds that needs to pass
without a call to run() from a group property value changing.  As the
PCIeDevice attributes are written close together by the host, this allows the
action to wait until the writes are done before selecting the index.

Additional details are in the [header
file](../../control/json/actions/pcie_card_floors.hpp)

### set_request_target_base_with_max
Determines the maximum value from the properties of the group of D-Bus objects
and sets the requested target base to this value. Only positive integer or
floating point types are supported as these are the only valid types for a fan
target to be based off of.

The `requested target base` value is the base value to apply a target delta
to.  By default, it's the current zone target unless modified by this action.

```
{
    "name": "set_request_target_base_with_max",
    "groups": [{
        "name": "fan targets",
        "interface": "xyz.openbmc_project.Fan.Target",
        "property": { "name": "Target" }
      }]
}
```

The above config will set the requested target base to the maximum Target
property value of all members of the 'fan targets' group.

### set_parameter_from_group_max
Sets a parameter value based on the maximum group property value.  The property
value can be modified before storing it if the JSON specifies a valid modifier
expression.

 ```
{
    "name": "set_parameter_from_group_max",
    "parameter_name": "proc_0_throttle_temp",
    "modifier": {
      "expression": "minus",
      "value": 4
    }
}
 ```

The above config will first find the max of its groups property values,
subtract 4, and then store the resulting value in the `proc_0_throttle_temp`
parameter.

### target_from_group_max

The action sets target of Zone to a value corresponding to the maximum
value from maximum group property value. The mapping is based on a provided
table. If there are more than one event using this action, the maximum speed
derived from the mapping of all groups will be set to the zone's target.

...
{
    "name": "target_from_group_max",
    "groups": [
        {
          "name": "zone0_ambient",
          "interface": "xyz.openbmc_project.Sensor.Value",
          "property": { "name": "Value" }
        }
    ],
    "neg_hysteresis": 1,
    "pos_hysteresis": 0,
    "map": [
        { "value": 10.0, "target": 38.0 },
        ...
    ]
}

The above JSON will cause the action to read the property specified in the
group "zone0_ambient" from all members of the group. The change in the group's
members value will be checked against "neg_hysteresis" and "pos_hysteresis"
to decide if it is worth taking action. "neg_hysteresis" is for the increasing
case and "pos_hysteresis" is for the decreasing case. The maximum property value
in the group will be mapped to the "map" to get the output "target".
Each configured event using this action will be provided with a key in a static map
to store its mapping result. The static map will be shared across the events of this
action. Therefore, the updated "target" value derived from "zone0_ambient" will be
stored in that static map with its own key. Each time it calls this action running
for each event, after the new value is updated to the static map, the maximum value
from it will be used to set to the Zone's target.

### call_actions_based_on_timer
This action starts and stops a timer that runs a list of actions whenever the
timer expires.  A timer can be either `oneshot` or `repeating`.

When all groups have a configured value to compare against, that will
be compared against all members within each group to start/stop the
timer. When all group members have a given value and it matches what's
in the cache, the timer is started and if any do not match, the timer is
stopped.

When any group does not have a configured value to be compared against,
the groups' service owned state is used to start/stop the timer. When
any service providing a group member is not owned, the timer is started
and if all members' services are owned, the timer is stopped.

Consider the following action config:
```
{
    "name": "call_actions_based_on_timer",
    "timer": {
        "interval": 5000000,
        "type": "oneshot"
    },
    "actions": [{
        "name": "test"
    }]
}

```
If its group configuration has a property value listed, like:

```
{
    "name": "fan inventory",
    "interface": "xyz.openbmc_project.Inventory.Item",
    "property": { "name": "Present", "value": true }
}
```
Then a oneshot timer of 5000000us will be started when every member of the fan
inventory group has a value of true.  Otherwise, the timer will be stopped if
it's running.

If the group configuration has no property value listed, like:

```
{
    "name": "fan inventory",
    "interface": "xyz.openbmc_project.Inventory.Item",
    "property": { "name": "Present" }
}
```
Then the timer will be started when any service providing a group member isn't
owned (on D-Bus).  Otherwise, it will stop the timer if it's running.

### get_managed_objects
This action adds the members of its groups to the object cache by using the
GetManagedObjects D-Bus method to find and add the results.  When that is done,
it then runs any actions listed in the JSON.

This allows an action to run with the latest values in the cache without having
to subscribe to propertiesChanged for them all.

```
{
   "name": "get_managed_objects",
   "groups": [
     {
       "name": "proc temps",
       "interface": "xyz.openbmc_project.Sensor.Value",
       "property": { "name": "Value" }
     }
   ],
   "actions": [
     {
       "name": "set_net_increase_target",
       "state": 30,
       "delta": 100
     }
   ]
}
```

The above config will make the GetManagedObjects call on all services that own
the configured groups and then add all resulting property values to the object
cache.  After that, it will call the `set_net_increase_target` action using the
same groups.

## Modifiers
Modifiers are used by some actions to help calculate values.

### minus
Subtract the `value` field from the passed in value.

```
"modifier": {
    "expression": "minus",
    "value": 4
}
```

The above config subtracts 4 from what is passed to it.

### less_than
Returns a value from a data table that is selected when the argument passed in
is less than the `arg_value` entry in the table row.  If there is a
`default_value` field supplied, then that will be returned if the argument is
greater than the `arg_value` of the last row.

```
"modifier": {
  "operator": "less_than",
  "default_value": 10000,
  "value": [
      { "arg_value": 500, "parameter_value": 1 },
      { "arg_value": 1000, "parameter_value": 2 },
      { "arg_value": 1500, "parameter_value": 3 }
  ]
}
```

The above config returns 1 if the arg passed is less than 500, 2 if less than
1000, and 3 if less than 1500.  Otherwise returns 10000, the default value.