commit	7ba70c820ed1ff5c19ea2af337ecad82732f383d	[log] [tgz]
author	Alexander Hansen <alexander.hansen@9elements.com>	Tue Jul 23 13:46:25 2024 +0200
committer	Alexander Hansen <alexander.hansen@9elements.com>	Wed Aug 21 09:46:01 2024 +0200
tree	84582ec7db46e8d2eeb79f49408f440197afa007
parent	a6f9a41ec99d92daf02fc820b17bc9505b183f8c [diff]

tree: 84582ec7db46e8d2eeb79f49408f440197afa007

README.md

phosphor-led-manager

This project manages LED groups on dbus. Sometimes many LEDs must be driven together to indicate some system state.

For example, there can be multiple identify LEDs. When the user wants to identify the system, they should all light up together.

Configuration

The configuration can happen via json or yaml.

Configuration: LED Priority

Each LED can have "Priority" as "Blink" or "On". If this property is defined, it should be defined on each instance of the LED in the config.

When multiple LED groups are asserted and contain the same LED, "Priority" determines the state of the LED.

For example, Group 1 says LED1 should be "Blink", and Group 2 says it should be "On". LED1 will then have the state declared in "Priority".

Configuration Example (JSON)

This is our configuration file. It describes 2 LEDs for the 'enclosure_identify' group, with their respective states and duty cycles.

{
  "leds": [
    {
      "group": "enclosure_identify",
      "members": [
        {
          "Name": "pca955x_front_sys_id0",
          "Action": "On",
          "DutyOn": 50,
          "Period": 0,
          "Priority": "Blink"
        },
        {
          "Name": "led_rear_enc_id0",
          "Action": "On",
          "DutyOn": 50,
          "Period": 0,
          "Priority": "Blink"
        }
      ]
    }
  ]
}

Then start the program with

~# ./phosphor-led-manager --config example.json

Dbus interface

When starting the program, our LED group shows up on dbus. Usually there will be many more groups.

$ busctl tree xyz.openbmc_project.LED.GroupManager
`- /xyz
  `- /xyz/openbmc_project
    `- /xyz/openbmc_project/led
      `- /xyz/openbmc_project/led/groups
        `- /xyz/openbmc_project/led/groups/enclosure_identify


$ busctl introspect xyz.openbmc_project.LED.GroupManager /xyz/openbmc_project/led/groups/enclosure_identify
NAME                                TYPE      SIGNATURE RESULT/VALUE FLAGS
...
xyz.openbmc_project.Led.Group       interface -         -            -
.Asserted                           property  b         false        emits-change writable

In the above output, the usual org.freedesktop.* interfaces have been removed to keep it readable.

We can now drive the entire group by setting it's 'Asserted' property on dbus.

$ busctl set-property \
xyz.openbmc_project.LED.GroupManager \
/xyz/openbmc_project/led/groups/enclosure_identify \
xyz.openbmc_project.Led.Group Asserted b true

The program can then use the xyz.openbmc_project.Led.Physical dbus interface exposed by phosphor-led-sysfs to set each LED state.

How to Build

meson setup build
cd build
ninja