def GetDeviceStringProperty(dev_ref, key):
  """Reads string property from the HID device."""
  cf_key = CFStr(key)
  type_ref = iokit.IOHIDDeviceGetProperty(dev_ref, cf_key)
  cf.CFRelease(cf_key)
  if not type_ref:
    return None

  if cf.CFGetTypeID(type_ref) != cf.CFStringGetTypeID():
    raise errors.OsHidError('Expected string type, got {}'.format(
        cf.CFGetTypeID(type_ref)))

  type_ref = ctypes.cast(type_ref, CF_STRING_REF)
  out = ctypes.create_string_buffer(DEVICE_STRING_PROPERTY_BUFFER_SIZE)
  ret = cf.CFStringGetCString(type_ref, out, DEVICE_STRING_PROPERTY_BUFFER_SIZE,
                              K_CF_STRING_ENCODING_UTF8)
  if not ret:
    return None

  return out.value.decode('utf8')
Reads string property from the HID device.