feat: add device hotplug event notifications (USB on Linux)

pkg/devices/sources/usb_linux.go

@@ -0,0 +1,198 @@
+//go:build linux
+
+package sources
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"os/exec"
+	"strings"
+	"sync"
+
+	"github.com/sipeed/picoclaw/pkg/devices/events"
+	"github.com/sipeed/picoclaw/pkg/logger"
+)
+
+var usbClassToCapability = map[string]string{
+	"00": "Interface Definition (by interface)",
+	"01": "Audio",
+	"02": "CDC Communication (Network Card/Modem)",
+	"03": "HID (Keyboard/Mouse/Gamepad)",
+	"05": "Physical Interface",
+	"06": "Image (Scanner/Camera)",
+	"07": "Printer",
+	"08": "Mass Storage (USB Flash Drive/Hard Disk)",
+	"09": "USB Hub",
+	"0a": "CDC Data",
+	"0b": "Smart Card",
+	"0e": "Video (Camera)",
+	"dc": "Diagnostic Device",
+	"e0": "Wireless Controller (Bluetooth)",
+	"ef": "Miscellaneous",
+	"fe": "Application Specific",
+	"ff": "Vendor Specific",
+}
+
+type USBMonitor struct {
+	cmd    *exec.Cmd
+	cancel context.CancelFunc
+	mu     sync.Mutex
+}
+
+func NewUSBMonitor() *USBMonitor {
+	return &USBMonitor{}
+}
+
+func (m *USBMonitor) Kind() events.Kind {
+	return events.KindUSB
+}
+
+func (m *USBMonitor) Start(ctx context.Context) (<-chan *events.DeviceEvent, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	// udevadm monitor outputs: UDEV/KERNEL [timestamp] action devpath (subsystem)
+	// Followed by KEY=value lines, empty line separates events
+	// Use -s/--subsystem-match (eudev) or --udev-subsystem-match (systemd udev)
+	cmd := exec.CommandContext(ctx, "udevadm", "monitor", "--property", "--subsystem-match=usb")
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return nil, fmt.Errorf("udevadm stdout pipe: %w", err)
+	}
+
+	if err := cmd.Start(); err != nil {
+		return nil, fmt.Errorf("udevadm start: %w (is udevadm installed?)", err)
+	}
+
+	m.cmd = cmd
+	eventCh := make(chan *events.DeviceEvent, 16)
+
+	go func() {
+		defer close(eventCh)
+		scanner := bufio.NewScanner(stdout)
+		var props map[string]string
+		var action string
+		isUdev := false // Only UDEV events have complete info (ID_VENDOR, ID_MODEL); KERNEL events come first with less info
+
+		for scanner.Scan() {
+			line := scanner.Text()
+			if line == "" {
+				// End of event block - only process UDEV events (skip KERNEL to avoid duplicate/incomplete notifications)
+				if isUdev && props != nil && (action == "add" || action == "remove") {
+					if ev := parseUSBEvent(action, props); ev != nil {
+						select {
+						case eventCh <- ev:
+						case <-ctx.Done():
+							return
+						}
+					}
+				}
+				props = nil
+				action = ""
+				isUdev = false
+				continue
+			}
+
+			idx := strings.Index(line, "=")
+			// First line of block: "UDEV  [ts] action devpath" or "KERNEL[ts] action devpath" - no KEY=value
+			if idx <= 0 {
+				isUdev = strings.HasPrefix(strings.TrimSpace(line), "UDEV")
+				continue
+			}
+
+			// Parse KEY=value
+			key := line[:idx]
+			val := line[idx+1:]
+			if props == nil {
+				props = make(map[string]string)
+			}
+			props[key] = val
+
+			if key == "ACTION" {
+				action = val
+			}
+		}
+
+		if err := scanner.Err(); err != nil {
+			logger.ErrorCF("devices", "udevadm scan error", map[string]interface{}{"error": err.Error()})
+		}
+		cmd.Wait()
+	}()
+
+	return eventCh, nil
+}
+
+func (m *USBMonitor) Stop() error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if m.cmd != nil && m.cmd.Process != nil {
+		m.cmd.Process.Kill()
+		m.cmd = nil
+	}
+	return nil
+}
+
+func parseUSBEvent(action string, props map[string]string) *events.DeviceEvent {
+	// Only care about add/remove for physical devices (not interfaces)
+	subsystem := props["SUBSYSTEM"]
+	if subsystem != "usb" {
+		return nil
+	}
+	// Skip interface events - we want device-level only to avoid duplicates
+	devType := props["DEVTYPE"]
+	if devType == "usb_interface" {
+		return nil
+	}
+	// Prefer usb_device, but accept if DEVTYPE not set (varies by udev version)
+	if devType != "" && devType != "usb_device" {
+		return nil
+	}
+
+	ev := &events.DeviceEvent{
+		Raw: props,
+	}
+	switch action {
+	case "add":
+		ev.Action = events.ActionAdd
+	case "remove":
+		ev.Action = events.ActionRemove
+	default:
+		return nil
+	}
+	ev.Kind = events.KindUSB
+
+	ev.Vendor = props["ID_VENDOR"]
+	if ev.Vendor == "" {
+		ev.Vendor = props["ID_VENDOR_ID"]
+	}
+	if ev.Vendor == "" {
+		ev.Vendor = "Unknown Vendor"
+	}
+
+	ev.Product = props["ID_MODEL"]
+	if ev.Product == "" {
+		ev.Product = props["ID_MODEL_ID"]
+	}
+	if ev.Product == "" {
+		ev.Product = "Unknown Device"
+	}
+
+	ev.Serial = props["ID_SERIAL_SHORT"]
+	ev.DeviceID = props["DEVPATH"]
+	if bus := props["BUSNUM"]; bus != "" {
+		if dev := props["DEVNUM"]; dev != "" {
+			ev.DeviceID = bus + ":" + dev
+		}
+	}
+
+	// Map USB class to capability
+	if class := props["ID_USB_CLASS"]; class != "" {
+		ev.Capabilities = usbClassToCapability[strings.ToLower(class)]
+	}
+	if ev.Capabilities == "" {
+		ev.Capabilities = "USB Device"
+	}
+
+	return ev
+}