feat: release keyPress automatically

internal/usbgadget/hid_keyboard.go

@@ -173,6 +173,50 @@ func (u *UsbGadget) SetOnKeysDownChange(f func(state KeysDownState)) {
 	u.onKeysDownChange = &f
 }
 
+const autoReleaseKeyboardInterval = time.Millisecond * 300
+
+func (u *UsbGadget) scheduleAutoRelease(key byte) {
+	u.keysAutoReleaseLock.Lock()
+	defer u.keysAutoReleaseLock.Unlock()
+
+	if u.keysAutoReleaseTimer != nil {
+		u.keysAutoReleaseTimer.Stop()
+	}
+
+	u.keysAutoReleaseTimer = time.AfterFunc(autoReleaseKeyboardInterval, func() {
+		u.performAutoRelease(key)
+	})
+}
+
+func (u *UsbGadget) cancelAutoRelease() {
+	u.keysAutoReleaseLock.Lock()
+	defer u.keysAutoReleaseLock.Unlock()
+
+	if u.keysAutoReleaseTimer != nil {
+		u.keysAutoReleaseTimer.Stop()
+	}
+}
+
+func (u *UsbGadget) performAutoRelease(key byte) {
+	u.keysAutoReleaseLock.Lock()
+	defer u.keysAutoReleaseLock.Unlock()
+
+	select {
+	case <-u.keyboardStateCtx.Done():
+		return
+	default:
+	}
+
+	_, err := u.KeypressReport(key, false)
+	if err != nil {
+		u.log.Warn().Uint8("key", key).Msg("failed to auto-release keyboard key")
+	}
+
+	u.keysAutoReleaseTimer = nil
+
+	u.log.Trace().Uint8("key", key).Msg("auto release performed")
+}
+
 func (u *UsbGadget) listenKeyboardEvents() {
 	var path string
 	if u.keyboardHidFile != nil {
@@ -398,5 +442,11 @@ func (u *UsbGadget) KeypressReport(key byte, press bool) (KeysDownState, error)
 		u.log.Warn().Uint8("modifier", modifier).Uints8("keys", keys).Msg("Could not write keypress report to hidg0")
 	}
 
+	if press {
+		u.scheduleAutoRelease(key)
+	} else {
+		u.cancelAutoRelease()
+	}
+
 	return u.UpdateKeysDown(modifier, keys), err
 }

internal/usbgadget/usbgadget.go

@@ -68,6 +68,9 @@ type UsbGadget struct {
 	keyboardState byte          // keyboard latched state (NumLock, CapsLock, ScrollLock, Compose, Kana)
 	keysDownState KeysDownState // keyboard dynamic state (modifier keys and pressed keys)
 
+	keysAutoReleaseLock  sync.Mutex
+	keysAutoReleaseTimer *time.Timer
+
 	keyboardStateLock   sync.Mutex
 	keyboardStateCtx    context.Context
 	keyboardStateCancel context.CancelFunc
@@ -149,3 +152,35 @@ func newUsbGadget(name string, configMap map[string]gadgetConfigItem, enabledDev
 
 	return g
 }
+
+// Close cleans up resources used by the USB gadget
+func (u *UsbGadget) Close() error {
+	// Cancel keyboard state context
+	if u.keyboardStateCancel != nil {
+		u.keyboardStateCancel()
+	}
+
+	// Stop auto-release timer
+	u.keysAutoReleaseLock.Lock()
+	if u.keysAutoReleaseTimer != nil {
+		u.keysAutoReleaseTimer.Stop()
+		u.keysAutoReleaseTimer = nil
+	}
+	u.keysAutoReleaseLock.Unlock()
+
+	// Close HID files
+	if u.keyboardHidFile != nil {
+		u.keyboardHidFile.Close()
+		u.keyboardHidFile = nil
+	}
+	if u.absMouseHidFile != nil {
+		u.absMouseHidFile.Close()
+		u.absMouseHidFile = nil
+	}
+	if u.relMouseHidFile != nil {
+		u.relMouseHidFile.Close()
+		u.relMouseHidFile = nil
+	}
+
+	return nil
+}