Add a helper to get a GUsbDevice from a FuUdevDevice

libfwupdplugin/fu-udev-device.c

@@ -2081,6 +2081,75 @@ fu_udev_device_get_children_with_subsystem(FuUdevDevice *self, const gchar *cons
 	return g_steal_pointer(&out);
 }
 
+/**
+ * fu_udev_device_find_usb_device:
+ * @FuUdevDevice: a #FuUdevDevice
+ * @error: (nullable): optional return location for an error
+ *
+ * Gets the matching #GUsbDevice for the #GUdevDevice.
+ *
+ * NOTE: This should never be stored in the device class as an instance variable, as the lifecycle
+ * for `GUsbDevice` may be different to the `FuUdevDevice`. Every time the `GUsbDevice` is used
+ * this function should be called.
+ *
+ * Returns: (transfer full): a #GUsbDevice, or NULL if unset or invalid
+ *
+ * Since: 1.8.7
+ **/
+GUsbDevice *
+fu_udev_device_find_usb_device(FuUdevDevice *self, GError **error)
+{
+#if defined(HAVE_GUDEV) && defined(HAVE_GUSB)
+	FuUdevDevicePrivate *priv = GET_PRIVATE(self);
+	guint8 bus = 0;
+	guint8 address = 0;
+	g_autoptr(GUdevDevice) udev_device = g_object_ref(priv->udev_device);
+	g_autoptr(GUsbContext) usb_ctx = NULL;
+	g_autoptr(GUsbDevice) usb_device = NULL;
+
+	g_return_val_if_fail(FU_IS_UDEV_DEVICE(self), NULL);
+	g_return_val_if_fail(error == NULL || *error == NULL, NULL);
+
+	/* look at the current device and all the parent devices until we can find the USB data */
+	while (TRUE) {
+		g_autoptr(GUdevDevice) udev_device_parent = NULL;
+		bus = g_udev_device_get_sysfs_attr_as_int(udev_device, "busnum");
+		address = g_udev_device_get_sysfs_attr_as_int(udev_device, "devnum");
+		if (bus != 0 || address != 0)
+			break;
+		udev_device_parent = g_udev_device_get_parent(udev_device);
+		g_set_object(&udev_device, udev_device_parent);
+	}
+
+	/* nothing found */
+	if (bus == 0x0 && address == 0x0) {
+		g_set_error_literal(error,
+				    FWUPD_ERROR,
+				    FWUPD_ERROR_NOT_SUPPORTED,
+				    "No parent device with busnum and devnum");
+		return NULL;
+	}
+
+	/* match device */
+	usb_ctx = g_usb_context_new(error);
+	if (usb_ctx == NULL)
+		return NULL;
+	usb_device = g_usb_context_find_by_bus_address(usb_ctx, bus, address, error);
+	if (usb_device == NULL)
+		return NULL;
+#if G_USB_CHECK_VERSION(0, 4, 1)
+	g_usb_device_add_tag(usb_device, "is-transient");
+#endif
+	return g_steal_pointer(&usb_device);
+#else
+	g_set_error_literal(error,
+			    FWUPD_ERROR,
+			    FWUPD_ERROR_NOT_SUPPORTED,
+			    "Not supported as <gudev.h> or <gusb.h> is unavailable");
+	return NULL;
+#endif
+}
+
 static void
 fu_udev_device_get_property(GObject *object, guint prop_id, GValue *value, GParamSpec *pspec)
 {

libfwupdplugin/fu-udev-device.h

@@ -13,6 +13,13 @@
 #define GUdevDevice	   GObject
 #endif
 
+#ifdef HAVE_GUSB
+#include <gusb.h>
+#else
+#define GUsbContext GObject
+#define GUsbDevice  GObject
+#endif
+
 #include "fu-plugin.h"
 
 #define FU_TYPE_UDEV_DEVICE (fu_udev_device_get_type())
@@ -139,3 +146,6 @@ GPtrArray *
 fu_udev_device_get_children_with_subsystem(FuUdevDevice *self, const gchar *subsystem);
 FuUdevDevice *
 fu_udev_device_get_parent_with_subsystem(FuUdevDevice *self, const gchar *subsystem);
+
+GUsbDevice *
+fu_udev_device_find_usb_device(FuUdevDevice *self, GError **error) G_GNUC_WARN_UNUSED_RESULT;

libfwupdplugin/fu-usb-device.c

@@ -834,6 +834,13 @@ fu_udev_device_unbind_driver(FuDevice *device, GError **error)
 FuUsbDevice *
 fu_usb_device_new(FuContext *ctx, GUsbDevice *usb_device)
 {
+#if G_USB_CHECK_VERSION(0, 4, 3)
+	if (g_usb_device_has_tag(usb_device, "is-transient")) {
+		g_critical("cannot use a device built using fu_udev_device_find_usb_device() as "
+			   "the GUsbContext is different");
+		return NULL;
+	}
+#endif
 	return g_object_new(FU_TYPE_USB_DEVICE, "context", ctx, "usb-device", usb_device, NULL);
 }
 

libfwupdplugin/fwupdplugin.map

@@ -1139,6 +1139,7 @@ LIBFWUPDPLUGIN_1.8.6 {
 
 LIBFWUPDPLUGIN_1.8.7 {
   global:
+    fu_udev_device_find_usb_device;
     fu_udev_device_set_device_file;
   local: *;
 } LIBFWUPDPLUGIN_1.8.6;