vaapidecode: search driver in whitelist

If the backend driver vendor string is not in a white-list, and the
environment variable GST_VAAPI_ALL_DRIVERS is not set either, the decoder will
change it state from NULL to READY, hence the auto-plug mechanism will look
for another decoder.

This patch assumes the GstContext has already being shared along the pipeline
and the element has a valid GstVaapiDisplay instance.

https://bugzilla.gnome.org/show_bug.cgi?id=764673

gst/vaapi/gstvaapidecode.c

@@ -160,7 +160,7 @@ static const GstVaapiDecoderMap vaapi_decode_map[] = {
 };
 
 static GstElementClass *parent_class = NULL;
-GST_VAAPI_PLUGIN_BASE_DEFINE_SET_CONTEXT (parent_class);
+GST_VAAPI_PLUGIN_BASE_DEFINE_VMETHODS (parent_class);
 
 static gboolean gst_vaapidecode_update_sink_caps (GstVaapiDecode * decode,
     GstCaps * caps);
@@ -1265,6 +1265,7 @@ gst_vaapidecode_class_init (GstVaapiDecodeClass * klass)
   }
 
   element_class->set_context = gst_vaapi_base_set_context;
+  element_class->change_state = GST_DEBUG_FUNCPTR (gst_vaapi_base_change_state);
   gst_element_class_set_static_metadata (element_class, longname,
       "Codec/Decoder/Video", GST_PLUGIN_DESC,
       "Gwenole Beauchesne <gwenole.beauchesne@intel.com>, "

gst/vaapi/gstvaapipluginbase.c

@@ -35,6 +35,9 @@
 /* Default debug category is from the subclass */
 #define GST_CAT_DEFAULT (plugin->debug_category)
 
+/* Environment variable for disable driver white-list */
+#define GST_VAAPI_ALL_DRIVERS_ENV "GST_VAAPI_ALL_DRIVERS"
+
 /* GstVideoContext interface */
 static void
 plugin_set_display (GstVaapiPluginBase * plugin, GstVaapiDisplay * display)
@@ -76,6 +79,57 @@ gst_vaapi_plugin_base_set_context (GstVaapiPluginBase * plugin,
     plugin_set_display (plugin, display);
 }
 
+/**
+ * gst_vaapi_plugin_base_driver_is_whitelisted:
+ * @plugin: a #GstVaapiPluginBase instance
+ *
+ * Looks the VA-API driver vendors in an internal white-list.
+ *
+ * Returns: %TRUE if driver is in the white-list, otherwise %FALSE
+ **/
+gboolean
+gst_vaapi_plugin_base_driver_is_whitelisted (GstVaapiPluginBase * plugin)
+{
+  const gchar *vendor;
+  guint i;
+  GstVaapiDisplay *display;
+  static const gchar *whitelist[] = {
+    "Intel i965 driver",
+    "mesa gallium vaapi",
+    NULL
+  };
+
+  if (g_getenv (GST_VAAPI_ALL_DRIVERS_ENV))
+    return TRUE;
+
+  display = GST_VAAPI_PLUGIN_BASE_DISPLAY (plugin);
+  if (!display)
+    goto no_display;
+  vendor = gst_vaapi_display_get_vendor_string (display);
+  if (!vendor)
+    goto no_vendor;
+  for (i = 0; whitelist[i]; i++) {
+    if (g_ascii_strncasecmp (vendor, whitelist[i], strlen (whitelist[i])) == 0)
+      return TRUE;
+  }
+
+  GST_ERROR ("Unsupported VA driver: %s. Export environment variable "
+      GST_VAAPI_ALL_DRIVERS_ENV " to bypass", vendor);
+  return FALSE;
+
+  /* ERRORS */
+no_display:
+  {
+    GST_WARNING_OBJECT (plugin, "no VA-API display available");
+    return FALSE;
+  }
+no_vendor:
+  {
+    GST_WARNING_OBJECT (plugin, "no VA-API driver vendor description");
+    return FALSE;
+  }
+}
+
 void
 gst_vaapi_plugin_base_init_interfaces (GType g_define_type_id)
 {

gst/vaapi/gstvaapipluginbase.h

@@ -102,6 +102,10 @@ typedef struct _GstVaapiPluginBaseClass GstVaapiPluginBaseClass;
   (gst_vaapi_display_replace(&GST_VAAPI_PLUGIN_BASE_DISPLAY(plugin), \
        (new_display)))
 
+#define GST_VAAPI_PLUGIN_BASE_DEFINE_VMETHODS(parent_class) \
+  GST_VAAPI_PLUGIN_BASE_DEFINE_SET_CONTEXT(parent_class) \
+  GST_VAAPI_PLUGIN_BASE_DEFINE_CHANGE_STATE(parent_class)
+
 #define GST_VAAPI_PLUGIN_BASE_DEFINE_SET_CONTEXT(parent_class) \
   static void \
   gst_vaapi_base_set_context (GstElement * element, GstContext * context) \
@@ -112,6 +116,31 @@ typedef struct _GstVaapiPluginBaseClass GstVaapiPluginBaseClass;
     GST_ELEMENT_CLASS (parent_class)->set_context (element, context); \
   }
 
+#define GST_VAAPI_PLUGIN_BASE_DEFINE_CHANGE_STATE(parent_class) \
+  static GstStateChangeReturn \
+  gst_vaapi_base_change_state (GstElement * element, \
+      GstStateChange transition) \
+  { \
+    GstStateChangeReturn ret; \
+    \
+    ret = GST_ELEMENT_CLASS (parent_class)->change_state (element, \
+        transition);  \
+    if (ret == GST_STATE_CHANGE_FAILURE) \
+      return ret; \
+    \
+    switch (transition) { \
+      case GST_STATE_CHANGE_NULL_TO_READY:{ \
+        GstVaapiPluginBase *const plugin = GST_VAAPI_PLUGIN_BASE (element); \
+        if (!gst_vaapi_plugin_base_driver_is_whitelisted (plugin)) \
+          ret = GST_STATE_CHANGE_FAILURE; \
+        break; \
+      } \
+      default: \
+        break; \
+    }          \
+    return ret; \
+  }
+
 struct _GstVaapiPluginBase
 {
   /*< private >*/
@@ -230,6 +259,10 @@ GstFlowReturn
 gst_vaapi_plugin_base_get_input_buffer (GstVaapiPluginBase * plugin,
     GstBuffer * inbuf, GstBuffer ** outbuf_ptr);
 
+G_GNUC_INTERNAL
+gboolean
+gst_vaapi_plugin_base_driver_is_whitelisted (GstVaapiPluginBase * plugin);
+
 G_GNUC_INTERNAL
 void
 gst_vaapi_plugin_base_set_context (GstVaapiPluginBase * plugin,