A quick and dirty implementation

light/rpi/basic_light.go

@@ -0,0 +1,68 @@
+package rpi
+
+import (
+	"fmt"
+	"sync"
+
+	"github.com/warthog618/gpiod"
+)
+
+// BasicLight is a BasicLight implementation for the Raspberry Pi
+type BasicLight struct {
+	pin      int
+	line     *gpiod.Line
+	manager  *Manager
+	isOn     bool
+	isOnLock sync.Mutex
+}
+
+// On turns on the light
+func (bl *BasicLight) On() error {
+	bl.isOnLock.Lock()
+	defer bl.isOnLock.Unlock()
+
+	if bl.isOn {
+		return nil
+	}
+
+	err := bl.line.SetValue(0)
+	if err != nil {
+		return fmt.Errorf("failed to set pin %d to low (on): %w", bl.pin, err)
+	}
+
+	bl.isOn = true
+
+	return nil
+}
+
+// Off turns off the light
+func (bl *BasicLight) Off() error {
+	bl.isOnLock.Lock()
+	defer bl.isOnLock.Unlock()
+
+	if !bl.isOn {
+		return nil
+	}
+
+	err := bl.line.SetValue(1)
+	if err != nil {
+		return fmt.Errorf("failed to set pin %d to high (on): %w", bl.pin, err)
+	}
+
+	bl.isOn = false
+
+	return nil
+}
+
+// State of whether the light is on or off
+func (bl *BasicLight) State() (isOn bool, err error) {
+	bl.isOnLock.Lock()
+	defer bl.isOnLock.Unlock()
+
+	return bl.isOn, nil
+}
+
+// Close underlying open connection
+func (bl *BasicLight) Close() error {
+	return bl.manager.closeLine(bl.pin)
+}

light/rpi/manager.go

@@ -0,0 +1,121 @@
+package rpi
+
+import (
+	"errors"
+	"fmt"
+	"sync"
+
+	"github.com/warthog618/gpiod"
+)
+
+const (
+	// DefaultChipName to try to use if one is not provided
+	DefaultChipName = "gpiochip0"
+)
+
+var (
+	// ErrLineAlreadyRequested denotes that the requested line is not available because it has already been requested and not Closed
+	ErrLineAlreadyRequested = errors.New("line has already been requested")
+
+	// ErrLineNotRequested denotes that the given line cannot be acted on because it was not previously requested
+	ErrLineNotRequested = errors.New("line was not previously requested")
+)
+
+// ManagerConfig configuration for a Manager
+type ManagerConfig struct {
+	ChipName string
+}
+
+// GetChipName from the config
+func (mc *ManagerConfig) GetChipName() string {
+	if mc.ChipName == "" {
+		return DefaultChipName
+	}
+
+	return mc.ChipName
+}
+
+// Manager for overarching raspberry pi GPIO management
+type Manager struct {
+	config    *ManagerConfig
+	chip      *gpiod.Chip
+	lines     map[int]*gpiod.Line
+	linesLock sync.Mutex
+}
+
+// NewManager creates a new Manager instance for the given config
+func NewManager(config ManagerConfig) (*Manager, error) {
+	chip, err := gpiod.NewChip(config.GetChipName())
+	if err != nil {
+		return nil, fmt.Errorf("failed to open GPIO chip %s: %w", config.GetChipName(), err)
+	}
+
+	return &Manager{
+		config: &config,
+		chip:   chip,
+		lines:  make(map[int]*gpiod.Line),
+	}, nil
+}
+
+// GetBasicLight for the given pin if available
+func (m *Manager) GetBasicLight(pin int) (*BasicLight, error) {
+	line, err := m.requestLine(pin)
+	if err != nil {
+		return nil, err
+	}
+
+	return &BasicLight{
+		pin:     pin,
+		line:    line,
+		manager: m,
+	}, nil
+}
+
+func (m *Manager) requestLine(pin int) (*gpiod.Line, error) {
+	m.linesLock.Lock()
+	defer m.linesLock.Unlock()
+
+	_, exists := m.lines[pin]
+	if exists {
+		return nil, fmt.Errorf("%w pin %d", ErrLineAlreadyRequested, pin)
+	}
+
+	line, err := m.chip.RequestLine(pin, gpiod.AsOutput(0))
+	if err != nil {
+		return nil, fmt.Errorf("failed to request line for pin %d: %w", pin, err)
+	}
+
+	m.lines[pin] = line
+
+	return line, nil
+}
+
+func (m *Manager) closeLine(pin int) error {
+	m.linesLock.Lock()
+	defer m.linesLock.Unlock()
+
+	return m.closeLineHelper(pin)
+}
+
+func (m *Manager) closeLineHelper(pin int) error {
+	line := m.lines[pin]
+	if line == nil {
+		return fmt.Errorf("%w pin %d", ErrLineNotRequested, pin)
+	}
+
+	delete(m.lines, pin)
+
+	return line.Close()
+}
+
+// Close this Manager and all of its associated lines
+func (m *Manager) Close() error {
+	m.linesLock.Lock()
+	defer m.linesLock.Unlock()
+
+	for pin := range m.lines {
+		m.closeLineHelper(pin)
+	}
+
+	return m.chip.Close()
+}