led: support led functionality on the bbb

leddriver.go

@@ -0,0 +1,172 @@
+package embd
+
+import (
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strconv"
+	"strings"
+)
+
+type LEDMap map[string][]string
+
+type ledDriver struct {
+	ledMap LEDMap
+
+	initializedLEDs map[string]LED
+}
+
+func newLEDDriver(ledMap LEDMap) LEDDriver {
+	return &ledDriver{
+		ledMap:          ledMap,
+		initializedLEDs: map[string]LED{},
+	}
+}
+
+func (d *ledDriver) lookup(k interface{}) (string, error) {
+	var ks string
+	switch key := k.(type) {
+	case int:
+		ks = strconv.Itoa(key)
+	case string:
+		ks = key
+	case fmt.Stringer:
+		ks = key.String()
+	default:
+		return "", errors.New("led: invalid key type")
+	}
+
+	for id := range d.ledMap {
+		for _, alias := range d.ledMap[id] {
+			if alias == ks {
+				return id, nil
+			}
+		}
+	}
+
+	return "", fmt.Errorf("led: no match found for %q", k)
+}
+
+func (d *ledDriver) LED(k interface{}) (LED, error) {
+	id, err := d.lookup(k)
+	if err != nil {
+		return nil, err
+	}
+
+	led := newLED(id)
+	d.initializedLEDs[id] = led
+
+	return led, nil
+}
+
+func (d *ledDriver) Close() error {
+	for _, led := range d.initializedLEDs {
+		if err := led.Close(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+type led struct {
+	id string
+
+	brightness *os.File
+
+	initialized bool
+}
+
+func newLED(id string) LED {
+	return &led{id: id}
+}
+
+func (l *led) init() error {
+	if l.initialized {
+		return nil
+	}
+
+	var err error
+	if l.brightness, err = l.brightnessFile(); err != nil {
+		return err
+	}
+
+	l.initialized = true
+
+	return nil
+}
+
+func (l *led) brightnessFilePath() string {
+	return fmt.Sprintf("/sys/class/leds/%v/brightness", l.id)
+}
+
+func (l *led) openFile(path string) (*os.File, error) {
+	return os.OpenFile(path, os.O_RDWR, os.ModeExclusive)
+}
+
+func (l *led) brightnessFile() (*os.File, error) {
+	return l.openFile(l.brightnessFilePath())
+}
+
+func (l *led) On() error {
+	if err := l.init(); err != nil {
+		return err
+	}
+
+	_, err := l.brightness.WriteString("1")
+	return err
+}
+
+func (l *led) Off() error {
+	if err := l.init(); err != nil {
+		return err
+	}
+
+	_, err := l.brightness.WriteString("0")
+	return err
+}
+
+func (l *led) isOn() (bool, error) {
+	l.brightness.Seek(0, 0)
+	bytes, err := ioutil.ReadAll(l.brightness)
+	if err != nil {
+		return false, err
+	}
+	str := string(bytes)
+	str = strings.TrimSpace(str)
+	if str == "1" {
+		return true, nil
+	}
+	return false, nil
+}
+
+func (l *led) Toggle() error {
+	if err := l.init(); err != nil {
+		return err
+	}
+
+	state, err := l.isOn()
+	if err != nil {
+		return err
+	}
+
+	if state {
+		return l.Off()
+	}
+	return l.On()
+}
+
+func (l *led) Close() error {
+	if !l.initialized {
+		return nil
+	}
+
+	if err := l.brightness.Close(); err != nil {
+		return err
+	}
+
+	l.initialized = false
+
+	return nil
+}