This document describes how to add LED support for your machine based upon the OpenBMC LED Architecture document. LED group management is done automatically for machines that support the use of the MRW and is beyond the scope of this document.
Service xyx.openbmc_project.LED.GroupManager Path /xyz/openbmc_project/led/groups/<label> Interfaces xyz.openbmc_project.Led.Group Signals: none Attribute: Asserted (boolean)
PUT /xyz/openbmc_project/led/groups/<group>/attr/Asserted
The LED group state can be changed by setting the Asserted value to boolean 0 or 1. In the following example, the lamp_test group is being asserted...
curl -b cjar -k -X PUT -H "Content-Type: application/json" -d '{"data": 1}' \
https://${bmc}/xyz/openbmc_project/led/groups/lamp_test/attr/Asserted
Starting with Redfish v2020.3, Redfish resources have LocationIndicatorActive property, which is used to identify a particular resource. This is for LED Identify operation only.
All applicable Inventory D-Bus objects would have a forward association mapping to LED Group D-Bus object, namely:
- identify_led_group
All applicable LED Group D-Bus objects would have an association mapping to inventory D-Bus object, namely:
- identify_inventory_object
When a LocationIndicatorActive GET operation is performed on the resource, bmcweb does below operations:
identify_led_group on the Inventory D-Bus objectasserted property from the D-Bus object that is pointed to by identify_led_groupWhen a LocationIndicatorActive PATCH operation is performed on the resource, bmcweb does below operations:
identify_led_group on the Inventory D-Bus objectasserted property on the D-Bus object that is pointed to by identify_led_groupFor representing the fault status of a resource, Redfish Health property is used. All applicable Inventory D-Bus objects would have a forward association mapping to LED Group D-Bus object, namely;
- fault_led_group
All applicable LED Group D-Bus objects would have an association mapping to inventory D-Bus object, namely:
- fault_inventory_object
When a component fault is detected, the responsible code sets the Functional property of xyz.openbmc_project.State.Decorator.OperationalStatus to false on the Inventory D-Bus object.
When LED manager gets PropertyChanged signal, it does the following:
Look for an association fault_led_group on the Inventory D-Bus object
Turn on/off the fault LED group depending on the value of Functional false would mean turn ON the LED group true would mean turn OFF the LED group
bmcweb already has a design to look for Functional property and set the Health property.
There are two significant layers for LED operations. The physical and the logical. The LED Group Manager communicates with the physical LED Manager to drive the physical LEDs. The logical groups are defined in the machine's led.yaml file. LED Group manager consumes this and creates D-Bus/REST interfaces for the individual LEDs that are part of the group.
Physical LED wiring is defined in the leds section of the machine's device tree. See the Palmetto DTS as an example.
Add a fault LED to the device tree with a corresponding gpio pin...
leds {
compatible = "gpio-leds";
fault {
gpios = <&gpio ASPEED_GPIO(N, 2) GPIO_ACTIVE_LOW>;
};
}
The kernel will then create...
ls -l /sys/class/leds/fault/ total 0 -rw-r--r-- 1 root root 4096 Jun 21 20:04 brightness lrwxrwxrwx 1 root root 0 Jun 21 20:29 device -> ../../../leds -r--r--r-- 1 root root 4096 Jun 21 20:29 max_brightness drwxr-xr-x 2 root root 0 Jun 21 20:29 power lrwxrwxrwx 1 root root 0 Jun 21 20:04 subsystem -> ../../../../../class/leds -rw-r--r-- 1 root root 4096 Jun 21 20:04 trigger -rw-r--r-- 1 root root 4096 Jun 21 20:04 uevent
An LED Group can contain zero or more LEDs and is defined in the machines led.yaml. The default one will likely need to be tailored to your machines layout. Customized yaml files are placed into the machines specific Yocto location. As an example:
meta-ibm/meta-palmetto/recipes-phosphor/leds/palmetto-led-manager-config/led.yaml
The parent properties in the yaml file will be created below /xyz/openbmc_project/led/groups/. The children properties need to map to an LED name in /sys/class/leds.
In the example, below two URIs would be created: /xyz/openbmc_project/led/groups/enclosure_fault and /xyz/openbmc_project/led/groups/lamp_test. Both act on the same physical LED fault but do so differently. The lamp_test would also drive a blink signal to the physical power LED if one was created.
EnclosureFault:
fault:
Action: 'On'
DutyOn: 50
Period: 0
lamp_test:
fault:
Action: 'Blink'
DutyOn: 20
Period: 100
power:
Action: 'Blink'
DutyOn: 20
Period: 100
OpenBMC Architecture requires specific LED Groups to be created and are documented in the D-Bus interface.
Create a tailored LED manager file
E.g. meta-ibm/meta-romulus/recipes-phosphor/leds/romulus-led-manager-config-native.bb
SUMMARY = "Phosphor LED Group Management for Romulus"
PR = "r1"
inherit native
inherit obmc-phosphor-utils
inherit obmc-phosphor-license
PROVIDES += "virtual/phosphor-led-manager-config-native"
SRC_URI += "file://led.yaml"
S = "${WORKDIR}"
# Overwrites the default led.yaml
do_install() {
SRC=${S}
DEST=${D}${datadir}/phosphor-led-manager
install -D ${SRC}/led.yaml ${DEST}/led.yaml
}
Change your machine's preferred provider for the led-manager in the conf file
E.g. meta-ibm/meta-romulus/conf/machine/romulus.conf
PREFERRED_PROVIDER_virtual/phosphor-led-manager-config-native = "romulus-led-manager-config-native"