fp-context: Use an env to define a whitelist of drivers to enable

This avoids that we pick unwanted drivers when running the tests in a
machine that has some supported device attached.

libfprint/fp-context.c

@@ -57,6 +57,35 @@ enum {
 };
 static guint signals[LAST_SIGNAL] = { 0 };
 
+static const char *
+get_drivers_whitelist_env (void)
+{
+  return g_getenv ("FP_DRIVERS_WHITELIST");
+}
+
+static gboolean
+is_driver_allowed (const gchar *driver)
+{
+  g_auto(GStrv) whitelisted_drivers = NULL;
+  const char *fp_drivers_whitelist_env;
+  int i;
+
+  g_return_val_if_fail (driver, TRUE);
+
+  fp_drivers_whitelist_env = get_drivers_whitelist_env ();
+
+  if (!fp_drivers_whitelist_env)
+    return TRUE;
+
+  whitelisted_drivers = g_strsplit (fp_drivers_whitelist_env, ":", -1);
+
+  for (i = 0; whitelisted_drivers[i]; ++i)
+    if (g_strcmp0 (driver, whitelisted_drivers[i]) == 0)
+      return TRUE;
+
+  return FALSE;
+}
+
 static void
 async_device_init_done_cb (GObject *source_object, GAsyncResult *res, gpointer user_data)
 {
@@ -242,9 +271,25 @@ fp_context_init (FpContext *self)
 {
   g_autoptr(GError) error = NULL;
   FpContextPrivate *priv = fp_context_get_instance_private (self);
+  guint i;
 
   priv->drivers = fpi_get_driver_types ();
 
+  if (get_drivers_whitelist_env ())
+    {
+      for (i = 0; i < priv->drivers->len;)
+        {
+          GType driver = g_array_index (priv->drivers, GType, i);
+          g_autoptr(GTypeClass) type_class = g_type_class_ref (driver);
+          FpDeviceClass *cls = FP_DEVICE_CLASS (type_class);
+
+          if (!is_driver_allowed (cls->id))
+            g_array_remove_index (priv->drivers, i);
+          else
+            ++i;
+        }
+    }
+
   priv->devices = g_ptr_array_new_with_free_func (g_object_unref);
 
   priv->cancellable = g_cancellable_new ();

tests/meson.build

@@ -11,6 +11,9 @@ envs.prepend('LD_LIBRARY_PATH', join_paths(meson.build_root(), 'libfprint'))
 # random numbers rather than proper ones)
 envs.set('FP_DEVICE_EMULATION', '1')
 
+# Set a colon-separated list of native drivers we enable in tests
+envs.set('FP_DRIVERS_WHITELIST', 'virtual_image')
+
 envs.set('NO_AT_BRIDGE', '1')
 
 if get_option('introspection')
@@ -31,10 +34,13 @@ if get_option('introspection')
     ]
 
     foreach driver_test: drivers_tests
+        driver_envs = envs
+        driver_envs.set('FP_DRIVERS_WHITELIST', driver_test)
+
         test(driver_test,
             find_program('umockdev-test.py'),
             args: join_paths(meson.current_source_dir(), driver_test),
-            env: envs,
+            env: driver_envs,
             suite: ['drivers'],
             timeout: 10,
             depends: libfprint_typelib,