Implement LED control for Home Assistant Green (#164)

* Implement LED control for Home Assistant Green

Allow to control Home Assistant Green LEDs through D-Bus. Control the
state directly through sysfs.

* Fix linter issue

Author: agners

boards/boards.go

@@ -5,6 +5,7 @@ import (
 	"github.com/godbus/dbus/v5/introspect"
 	"github.com/godbus/dbus/v5/prop"
 
+	"github.com/home-assistant/os-agent/boards/green"
 	"github.com/home-assistant/os-agent/boards/supervised"
 	"github.com/home-assistant/os-agent/boards/yellow"
 	logging "github.com/home-assistant/os-agent/utils/log"
@@ -70,6 +71,8 @@ func InitializeDBus(conn *dbus.Conn, board string) {
 	// Initialize the board
 	if board == "Yellow" {
 		yellow.InitializeDBus(conn)
+	} else if board == "Green" {
+		green.InitializeDBus(conn)
 	} else if board == "Supervised" {
 		supervised.InitializeDBus(conn)
 	} else {

boards/green/green.go

@@ -0,0 +1,120 @@
+package green
+
+import (
+	"github.com/godbus/dbus/v5"
+	"github.com/godbus/dbus/v5/introspect"
+	"github.com/godbus/dbus/v5/prop"
+
+	"github.com/home-assistant/os-agent/utils/led"
+	logging "github.com/home-assistant/os-agent/utils/log"
+)
+
+const (
+	objectPath = "/io/hass/os/Boards/Green"
+	ifaceName  = "io.hass.os.Boards.Green"
+)
+
+var (
+	ledPower    led.LED = led.LED{Name: "power", DefaultTrigger: "default-on"}
+	ledActivity led.LED = led.LED{Name: "activity", DefaultTrigger: "activity"}
+	ledUser     led.LED = led.LED{Name: "user", DefaultTrigger: "heartbeat"}
+)
+
+type green struct {
+	conn  *dbus.Conn
+	props *prop.Properties
+}
+
+func getTriggerLED(led led.LED) bool {
+	value, err := led.GetTrigger()
+	if err != nil {
+		logging.Error.Print(err)
+	}
+	return value != "none"
+}
+
+func setTriggerLED(led led.LED, c *prop.Change) *dbus.Error {
+	logging.Info.Printf("Set Green %s LED to %t", led.Name, c.Value)
+	err := led.SetTrigger(c.Value.(bool))
+	if err != nil {
+		return dbus.MakeFailedError(err)
+	}
+	return nil
+}
+
+func setPowerLED(c *prop.Change) *dbus.Error {
+	return setTriggerLED(ledPower, c)
+}
+
+func setActivityLED(c *prop.Change) *dbus.Error {
+	return setTriggerLED(ledActivity, c)
+}
+
+func setUserLED(c *prop.Change) *dbus.Error {
+	return setTriggerLED(ledUser, c)
+}
+
+func InitializeDBus(conn *dbus.Conn) {
+	d := green{
+		conn: conn,
+	}
+
+	// Init base value
+	ledPowerValue := getTriggerLED(ledPower)
+	ledActivityValue := getTriggerLED(ledActivity)
+	ledUserValue := getTriggerLED(ledUser)
+
+	propsSpec := map[string]map[string]*prop.Prop{
+		ifaceName: {
+			"PowerLED": {
+				Value:    ledPowerValue,
+				Writable: true,
+				Emit:     prop.EmitTrue,
+				Callback: setPowerLED,
+			},
+			"ActivityLED": {
+				Value:    ledActivityValue,
+				Writable: true,
+				Emit:     prop.EmitTrue,
+				Callback: setActivityLED,
+			},
+			"UserLED": {
+				Value:    ledUserValue,
+				Writable: true,
+				Emit:     prop.EmitTrue,
+				Callback: setUserLED,
+			},
+		},
+	}
+
+	props, err := prop.Export(conn, objectPath, propsSpec)
+	if err != nil {
+		logging.Critical.Panic(err)
+	}
+	d.props = props
+
+	err = conn.Export(d, objectPath, ifaceName)
+	if err != nil {
+		logging.Critical.Panic(err)
+	}
+
+	node := &introspect.Node{
+		Name: objectPath,
+		Interfaces: []introspect.Interface{
+			introspect.IntrospectData,
+			prop.IntrospectData,
+			{
+				Name:       ifaceName,
+				Methods:    introspect.Methods(d),
+				Properties: props.Introspection(ifaceName),
+			},
+		},
+	}
+
+	err = conn.Export(introspect.NewIntrospectable(node), objectPath, "org.freedesktop.DBus.Introspectable")
+	if err != nil {
+		logging.Critical.Panic(err)
+	}
+
+	logging.Info.Printf("Exposing object %s with interface %s ...", objectPath, ifaceName)
+}

main.go

@@ -24,9 +24,10 @@ const (
 )
 
 var (
+	// version and baord are set at link time via -X flag
 	version       string = "dev"
-	enableCapture bool   = false
 	board         string = "unknown"
+	enableCapture bool   = false
 )
 
 func main() {

utils/led/led.go

@@ -0,0 +1,39 @@
+package led
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+type LED struct {
+	Name           string
+	DefaultTrigger string
+}
+
+func (led LED) GetTrigger() (string, error) {
+	ledTriggerFilePath := filepath.Join("/sys/class/leds/", led.Name, "trigger")
+	ledTrigger, err := os.ReadFile(ledTriggerFilePath)
+	if err != nil {
+		return "", err
+	}
+	return strings.TrimSpace(string(ledTrigger)), err
+}
+
+func (led LED) SetTrigger(newState bool) error {
+	ledTriggerFilePath := filepath.Join("/sys/class/leds/", led.Name, "trigger")
+	var newTrigger []byte
+
+	if newState {
+		newTrigger = []byte(led.DefaultTrigger)
+	} else {
+		newTrigger = []byte("none")
+	}
+
+	err := os.WriteFile(ledTriggerFilePath, newTrigger, 0600)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}