diff --git a/plugins/cros-ec/fu-cros-ec-usb-device.c b/plugins/cros-ec/fu-cros-ec-usb-device.c
index f68ecc5fc..e1c49d6c9 100644
--- a/plugins/cros-ec/fu-cros-ec-usb-device.c
+++ b/plugins/cros-ec/fu-cros-ec-usb-device.c
@@ -10,11 +10,96 @@
 
 #include "fu-cros-ec-usb-device.h"
 
+#define USB_SUBCLASS_GOOGLE_UPDATE	0x53
+#define USB_PROTOCOL_GOOGLE_UPDATE	0xff
+
+struct _FuCrosEcUsbDevice {
+	FuUsbDevice		parent_instance;
+	guint8			iface_idx; 	/* bInterfaceNumber */
+	guint8			ep_num;		/* bEndpointAddress */
+	guint16			chunk_len; 	/* wMaxPacketSize */
+
+};
+
 G_DEFINE_TYPE (FuCrosEcUsbDevice, fu_cros_ec_usb_device, FU_TYPE_USB_DEVICE)
 
+static gboolean
+fu_cros_ec_usb_device_find_interface (FuUsbDevice *device,
+				      GError **error)
+{
+	GUsbDevice *usb_device = fu_usb_device_get_dev (device);
+	FuCrosEcUsbDevice *self = FU_CROS_EC_USB_DEVICE (device);
+	g_autoptr(GPtrArray) intfs = NULL;
+
+	/* based on usb_updater2's find_interfacei() and find_endpoint() */
+
+	intfs = g_usb_device_get_interfaces (usb_device, error);
+	if (intfs == NULL)
+		return FALSE;
+	for (guint i = 0; i < intfs->len; i++) {
+		GUsbInterface *intf = g_ptr_array_index (intfs, i);
+		if (g_usb_interface_get_class (intf) == 255 &&
+		    g_usb_interface_get_subclass (intf) == USB_SUBCLASS_GOOGLE_UPDATE &&
+		    g_usb_interface_get_protocol (intf) == USB_PROTOCOL_GOOGLE_UPDATE) {
+			GUsbEndpoint *ep;
+			g_autoptr(GPtrArray) endpoints = NULL;
+
+			endpoints = g_usb_interface_get_endpoints (intf);
+			if (NULL == endpoints || 0 == endpoints->len)
+				continue;
+			ep = g_ptr_array_index (endpoints, 0);
+			self->iface_idx = g_usb_interface_get_number (intf);
+			self->ep_num = g_usb_endpoint_get_address (ep) & 0x7f;
+			self->chunk_len = g_usb_endpoint_get_maximum_packet_size (ep);
+
+			return TRUE;
+		}
+	}
+	g_set_error_literal (error,
+			     FWUPD_ERROR,
+			     FWUPD_ERROR_NOT_FOUND,
+			     "no update interface found");
+	return FALSE;
+}
+
 static gboolean
 fu_cros_ec_usb_device_open (FuUsbDevice *device, GError **error)
 {
+	GUsbDevice *usb_device = fu_usb_device_get_dev (device);
+	FuCrosEcUsbDevice *self = FU_CROS_EC_USB_DEVICE (device);
+
+	if (!g_usb_device_claim_interface (usb_device, self->iface_idx,
+					   G_USB_DEVICE_CLAIM_INTERFACE_BIND_KERNEL_DRIVER,
+					   error)) {
+		g_prefix_error (error, "failed to claim interface: ");
+		return FALSE;
+	}
+
+	/* success */
+	return TRUE;
+}
+
+static gboolean
+fu_cros_ec_usb_device_probe (FuUsbDevice *device, GError **error)
+{
+	FuCrosEcUsbDevice *self = FU_CROS_EC_USB_DEVICE (device);
+
+	/* very much like usb_updater2's usb_findit() */
+
+	if (!fu_cros_ec_usb_device_find_interface (device, error)) {
+		g_prefix_error (error, "failed to find update interface: ");
+		return FALSE;
+	}
+
+	if (self->chunk_len == 0) {
+		g_set_error (error,
+			     G_IO_ERROR,
+			     G_IO_ERROR_INVALID_DATA,
+			     "wMaxPacketSize isn't valid: %" G_GUINT16_FORMAT,
+			     self->chunk_len);
+		return FALSE;
+	}
+
 	/* success */
 	return TRUE;
 }
@@ -29,6 +114,16 @@ fu_cros_ec_usb_device_setup (FuDevice *device, GError **error)
 static gboolean
 fu_cros_ec_usb_device_close (FuUsbDevice *device, GError **error)
 {
+	GUsbDevice *usb_device = fu_usb_device_get_dev (device);
+	FuCrosEcUsbDevice *self = FU_CROS_EC_USB_DEVICE (device);
+
+	if (!g_usb_device_release_interface (usb_device, self->iface_idx,
+					     G_USB_DEVICE_CLAIM_INTERFACE_BIND_KERNEL_DRIVER,
+					     error)) {
+		g_prefix_error (error, "failed to release interface: ");
+		return FALSE;
+	}
+
 	/* success */
 	return TRUE;
 }
@@ -46,5 +141,6 @@ fu_cros_ec_usb_device_class_init (FuCrosEcUsbDeviceClass *klass)
 	FuUsbDeviceClass *klass_usb_device = FU_USB_DEVICE_CLASS (klass);
 	klass_device->setup = fu_cros_ec_usb_device_setup;
 	klass_usb_device->open = fu_cros_ec_usb_device_open;
+	klass_usb_device->probe = fu_cros_ec_usb_device_probe;
 	klass_usb_device->close = fu_cros_ec_usb_device_close;
 }
diff --git a/plugins/cros-ec/fu-cros-ec-usb-device.h b/plugins/cros-ec/fu-cros-ec-usb-device.h
index 6a437d418..ea3785b43 100644
--- a/plugins/cros-ec/fu-cros-ec-usb-device.h
+++ b/plugins/cros-ec/fu-cros-ec-usb-device.h
@@ -9,7 +9,7 @@
 #include "fu-plugin.h"
 
 #define FU_TYPE_CROS_EC_USB_DEVICE (fu_cros_ec_usb_device_get_type ())
-G_DECLARE_DERIVABLE_TYPE (FuCrosEcUsbDevice, fu_cros_ec_usb_device, FU, CROS_EC_USB_DEVICE, FuUsbDevice)
+G_DECLARE_FINAL_TYPE (FuCrosEcUsbDevice, fu_cros_ec_usb_device, FU, CROS_EC_USB_DEVICE, FuUsbDevice)
 
 struct _FuCrosEcUsbDeviceClass
 {