v4l2: use GstV4l2Error in gst_v4l2_open()

gst_v4l2_open() is called by gst_v4l2_device_provider_probe_device(),
where the GstV4l2Object is created without an associated GstElement.

If gst_v4l2_open() fails, it raises a bus message, but without an
element, a precondition check fails on
gst_element_message_full_with_details() generating a crash if running
with fatal-warnings debug mode.

GstV4l2Error is a helper to raise error bus messages when it is
appropiated. This patch changes the direct bus messages to this
helper, and the elements will actually send the error message.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/694>

sys/v4l2/gstv4l2deviceprovider.c

@@ -116,7 +116,7 @@ gst_v4l2_device_provider_probe_device (GstV4l2DeviceProvider * provider,
   v4l2obj = gst_v4l2_object_new (NULL, GST_OBJECT (provider),
       V4L2_BUF_TYPE_VIDEO_CAPTURE, device_path, NULL, NULL, NULL);
 
-  if (!gst_v4l2_open (v4l2obj))
+  if (!gst_v4l2_open (v4l2obj, NULL))
     goto destroy;
 
   gst_structure_set (props, "device.api", G_TYPE_STRING, "v4l2", NULL);

sys/v4l2/gstv4l2object.c

@@ -896,9 +896,9 @@ gst_v4l2_set_defaults (GstV4l2Object * v4l2object)
 }
 
 gboolean
-gst_v4l2_object_open (GstV4l2Object * v4l2object)
+gst_v4l2_object_open (GstV4l2Object * v4l2object, GstV4l2Error * error)
 {
-  if (gst_v4l2_open (v4l2object))
+  if (gst_v4l2_open (v4l2object, error))
     gst_v4l2_set_defaults (v4l2object);
   else
     return FALSE;

sys/v4l2/gstv4l2object.h

@@ -274,7 +274,7 @@ gboolean     gst_v4l2_object_get_property_helper       (GstV4l2Object *v4l2objec
                                                         guint prop_id, GValue * value,
                                                         GParamSpec * pspec);
 /* open/close */
-gboolean     gst_v4l2_object_open            (GstV4l2Object * v4l2object);
+gboolean     gst_v4l2_object_open            (GstV4l2Object * v4l2object, GstV4l2Error * error);
 gboolean     gst_v4l2_object_open_shared     (GstV4l2Object * v4l2object, GstV4l2Object * other);
 gboolean     gst_v4l2_object_close           (GstV4l2Object * v4l2object);
 
@@ -317,7 +317,7 @@ GstStructure * gst_v4l2_object_v4l2fourcc_to_structure (guint32 fourcc);
 
 /* TODO Move to proper namespace */
 /* open/close the device */
-gboolean     gst_v4l2_open           (GstV4l2Object * v4l2object);
+gboolean     gst_v4l2_open           (GstV4l2Object * v4l2object, GstV4l2Error * error);
 gboolean     gst_v4l2_dup            (GstV4l2Object * v4l2object, GstV4l2Object * other);
 gboolean     gst_v4l2_close          (GstV4l2Object * v4l2object);
 

sys/v4l2/gstv4l2radio.c

@@ -350,12 +350,12 @@ gst_v4l2radio_finalize (GstV4l2Radio * radio)
 }
 
 static gboolean
-gst_v4l2radio_open (GstV4l2Radio * radio)
+gst_v4l2radio_open (GstV4l2Radio * radio, GstV4l2Error * error)
 {
   GstV4l2Object *v4l2object;
 
   v4l2object = radio->v4l2object;
-  if (gst_v4l2_open (v4l2object))
+  if (gst_v4l2_open (v4l2object, error))
     return gst_v4l2radio_fill_channel_list (radio);
   else
     return FALSE;
@@ -406,9 +406,9 @@ gst_v4l2radio_set_defaults (GstV4l2Radio * radio)
 }
 
 static gboolean
-gst_v4l2radio_start (GstV4l2Radio * radio)
+gst_v4l2radio_start (GstV4l2Radio * radio, GstV4l2Error * error)
 {
-  if (!gst_v4l2radio_open (radio))
+  if (!gst_v4l2radio_open (radio, error))
     return FALSE;
 
   gst_v4l2radio_set_defaults (radio);
@@ -429,13 +429,14 @@ static GstStateChangeReturn
 gst_v4l2radio_change_state (GstElement * element, GstStateChange transition)
 {
   GstV4l2Radio *radio;
+  GstV4l2Error error = GST_V4L2_ERROR_INIT;
   GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;
 
   radio = GST_V4L2RADIO (element);
   switch (transition) {
     case GST_STATE_CHANGE_NULL_TO_READY:
       /*start radio */
-      if (!gst_v4l2radio_start (radio))
+      if (!gst_v4l2radio_start (radio, &error))
         ret = GST_STATE_CHANGE_FAILURE;
       break;
     case GST_STATE_CHANGE_PAUSED_TO_PLAYING:
@@ -457,6 +458,7 @@ gst_v4l2radio_change_state (GstElement * element, GstStateChange transition)
       break;
   }
 
+  gst_v4l2_error (radio, &error);
   return ret;
 }
 

sys/v4l2/gstv4l2sink.c

@@ -437,6 +437,7 @@ gst_v4l2sink_change_state (GstElement * element, GstStateChange transition)
 {
   GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;
   GstV4l2Sink *v4l2sink = GST_V4L2SINK (element);
+  GstV4l2Error error = GST_V4L2_ERROR_INIT;
 
   GST_DEBUG_OBJECT (v4l2sink, "%d -> %d",
       GST_STATE_TRANSITION_CURRENT (transition),
@@ -445,8 +446,10 @@ gst_v4l2sink_change_state (GstElement * element, GstStateChange transition)
   switch (transition) {
     case GST_STATE_CHANGE_NULL_TO_READY:
       /* open the device */
-      if (!gst_v4l2_object_open (v4l2sink->v4l2object))
+      if (!gst_v4l2_object_open (v4l2sink->v4l2object, &error)) {
+        gst_v4l2_error (v4l2sink, &error);
         return GST_STATE_CHANGE_FAILURE;
+      }
       break;
     default:
       break;

sys/v4l2/gstv4l2src.c

@@ -794,12 +794,15 @@ gst_v4l2src_change_state (GstElement * element, GstStateChange transition)
   GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;
   GstV4l2Src *v4l2src = GST_V4L2SRC (element);
   GstV4l2Object *obj = v4l2src->v4l2object;
+  GstV4l2Error error = GST_V4L2_ERROR_INIT;
 
   switch (transition) {
     case GST_STATE_CHANGE_NULL_TO_READY:
       /* open the device */
-      if (!gst_v4l2_object_open (obj))
+      if (!gst_v4l2_object_open (obj, &error)) {
+        gst_v4l2_error (v4l2src, &error);
         return GST_STATE_CHANGE_FAILURE;
+      }
       break;
     default:
       break;

sys/v4l2/gstv4l2transform.c

@@ -115,9 +115,11 @@ gst_v4l2_transform_get_property (GObject * object,
 static gboolean
 gst_v4l2_transform_open (GstV4l2Transform * self)
 {
+  GstV4l2Error error = GST_V4L2_ERROR_INIT;
+
   GST_DEBUG_OBJECT (self, "Opening");
 
-  if (!gst_v4l2_object_open (self->v4l2output))
+  if (!gst_v4l2_object_open (self->v4l2output, &error))
     goto failure;
 
   if (!gst_v4l2_object_open_shared (self->v4l2capture, self->v4l2output))
@@ -160,6 +162,8 @@ failure:
   gst_caps_replace (&self->probed_srccaps, NULL);
   gst_caps_replace (&self->probed_sinkcaps, NULL);
 
+  gst_v4l2_error (self, &error);
+
   return FALSE;
 }
 

sys/v4l2/gstv4l2videodec.c

@@ -119,11 +119,12 @@ static gboolean
 gst_v4l2_video_dec_open (GstVideoDecoder * decoder)
 {
   GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
+  GstV4l2Error error = GST_V4L2_ERROR_INIT;
   GstCaps *codec_caps;
 
   GST_DEBUG_OBJECT (self, "Opening");
 
-  if (!gst_v4l2_object_open (self->v4l2output))
+  if (!gst_v4l2_object_open (self->v4l2output, &error))
     goto failure;
 
   if (!gst_v4l2_object_open_shared (self->v4l2capture, self->v4l2output))
@@ -155,6 +156,8 @@ failure:
   gst_caps_replace (&self->probed_srccaps, NULL);
   gst_caps_replace (&self->probed_sinkcaps, NULL);
 
+  gst_v4l2_error (self, &error);
+
   return FALSE;
 }
 

sys/v4l2/gstv4l2videoenc.c

@@ -110,11 +110,12 @@ static gboolean
 gst_v4l2_video_enc_open (GstVideoEncoder * encoder)
 {
   GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);
+  GstV4l2Error error = GST_V4L2_ERROR_INIT;
   GstCaps *codec_caps;
 
   GST_DEBUG_OBJECT (self, "Opening");
 
-  if (!gst_v4l2_object_open (self->v4l2output))
+  if (!gst_v4l2_object_open (self->v4l2output, &error))
     goto failure;
 
   if (!gst_v4l2_object_open_shared (self->v4l2capture, self->v4l2output))
@@ -159,6 +160,8 @@ failure:
   gst_caps_replace (&self->probed_srccaps, NULL);
   gst_caps_replace (&self->probed_sinkcaps, NULL);
 
+  gst_v4l2_error (self, &error);
+
   return FALSE;
 }
 

sys/v4l2/v4l2_calls.c

@@ -516,7 +516,7 @@ gst_v4l2_adjust_buf_type (GstV4l2Object * v4l2object)
  * return value: TRUE on success, FALSE on error
  ******************************************************/
 gboolean
-gst_v4l2_open (GstV4l2Object * v4l2object)
+gst_v4l2_open (GstV4l2Object * v4l2object, GstV4l2Error * error)
 {
   struct stat st;
   int libv4l2_fd = -1;
@@ -605,46 +605,43 @@ gst_v4l2_open (GstV4l2Object * v4l2object)
   /* ERRORS */
 stat_failed:
   {
-    GST_ELEMENT_ERROR (v4l2object->element, RESOURCE, NOT_FOUND,
+    GST_V4L2_ERROR (error, RESOURCE, NOT_FOUND,
         (_("Cannot identify device '%s'."), v4l2object->videodev),
         GST_ERROR_SYSTEM);
     goto error;
   }
 no_device:
   {
-    GST_ELEMENT_ERROR (v4l2object->element, RESOURCE, NOT_FOUND,
+    GST_V4L2_ERROR (error, RESOURCE, NOT_FOUND,
         (_("This isn't a device '%s'."), v4l2object->videodev),
         GST_ERROR_SYSTEM);
     goto error;
   }
 not_open:
   {
-    GST_ELEMENT_ERROR (v4l2object->element, RESOURCE, OPEN_READ_WRITE,
+    GST_V4L2_ERROR (error, RESOURCE, OPEN_READ_WRITE,
         (_("Could not open device '%s' for reading and writing."),
             v4l2object->videodev), GST_ERROR_SYSTEM);
     goto error;
   }
 not_capture:
   {
-    GST_ELEMENT_ERROR (v4l2object->element, RESOURCE, NOT_FOUND,
+    GST_V4L2_ERROR (error, RESOURCE, NOT_FOUND,
-        (_("Device '%s' is not a capture device."),
+        (_("Device '%s' is not a capture device."), v4l2object->videodev),
-            v4l2object->videodev),
         ("Capabilities: 0x%x", v4l2object->device_caps));
     goto error;
   }
 not_output:
   {
-    GST_ELEMENT_ERROR (v4l2object->element, RESOURCE, NOT_FOUND,
+    GST_V4L2_ERROR (error, RESOURCE, NOT_FOUND,
-        (_("Device '%s' is not a output device."),
+        (_("Device '%s' is not a output device."), v4l2object->videodev),
-            v4l2object->videodev),
         ("Capabilities: 0x%x", v4l2object->device_caps));
     goto error;
   }
 not_m2m:
   {
-    GST_ELEMENT_ERROR (v4l2object->element, RESOURCE, NOT_FOUND,
+    GST_V4L2_ERROR (error, RESOURCE, NOT_FOUND,
-        (_("Device '%s' is not a M2M device."),
+        (_("Device '%s' is not a M2M device."), v4l2object->videodev),
-            v4l2object->videodev),
         ("Capabilities: 0x%x", v4l2object->device_caps));
     goto error;
   }