v4l2: Add helper to query input status

This is a wrapper around ENUM_INPUT renamed for readability.

Part-of: <!870>

sys/v4l2/gstv4l2object.h

@@ -327,6 +327,7 @@ gboolean     gst_v4l2_get_norm       (GstV4l2Object * v4l2object, v4l2_std_id *
 gboolean     gst_v4l2_set_norm       (GstV4l2Object * v4l2object, v4l2_std_id norm);
 gboolean     gst_v4l2_get_input      (GstV4l2Object * v4l2object, guint32 * input);
 gboolean     gst_v4l2_set_input      (GstV4l2Object * v4l2object, guint32 input);
+gboolean     gst_v4l2_query_input    (GstV4l2Object * v4l2object, struct v4l2_input * input);
 gboolean     gst_v4l2_get_output     (GstV4l2Object * v4l2object, guint32 * output);
 gboolean     gst_v4l2_set_output     (GstV4l2Object * v4l2object, guint32 output);
 
@@ -341,7 +342,6 @@ gboolean     gst_v4l2_set_attribute   (GstV4l2Object * v4l2object, int attribute
 gboolean     gst_v4l2_set_string_attribute (GstV4l2Object * v4l2object, int attribute_num, const char *value);
 gboolean     gst_v4l2_set_controls    (GstV4l2Object * v4l2object, GstStructure * controls);
 
-
 /* events */
 gboolean     gst_v4l2_subscribe_event (GstV4l2Object * v4l2object, guint32 event);
 gboolean     gst_v4l2_dequeue_event   (GstV4l2Object * v4l2object, struct v4l2_event *event);

sys/v4l2/v4l2_calls.c

@@ -1139,6 +1139,21 @@ input_failed:
   return FALSE;
 }
 
+gboolean
+gst_v4l2_query_input (GstV4l2Object * obj, struct v4l2_input * input)
+{
+  gint ret;
+
+  ret = obj->ioctl (obj->video_fd, VIDIOC_ENUMINPUT, input);
+  if (ret < 0) {
+    GST_WARNING_OBJECT (obj->dbg_obj, "Failed to read input state: %s (%i)",
+        g_strerror (errno), errno);
+    return FALSE;
+  }
+
+  return TRUE;
+}
+
 gboolean
 gst_v4l2_get_output (GstV4l2Object * v4l2object, guint32 * output)
 {