interface: Introduce methods to create and destroy instances.

In order to eventually hide the implementation details of the interface,
users will need to be able to create and destroy instances thereof.  This
patch adds the needed methods.

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Richard Cochran <richardcochran@gmail.com>

interface.c

@@ -4,8 +4,27 @@
  * @note Copyright (C) 2020 Richard Cochran <richardcochran@gmail.com>
  * @note SPDX-License-Identifier: GPL-2.0+
  */
+#include <stdlib.h>
 #include "interface.h"
 
+struct interface *interface_create(const char *name)
+{
+	struct interface *iface;
+
+	iface = calloc(1, sizeof(struct interface));
+	if (!iface) {
+		return NULL;
+	}
+	interface_set_name(iface, name);
+
+	return iface;
+}
+
+void interface_destroy(struct interface *iface)
+{
+	free(iface);
+}
+
 void interface_ensure_tslabel(struct interface *iface)
 {
 	if (!iface->ts_label[0]) {

interface.h

@@ -25,6 +25,19 @@ struct interface {
 	struct sk_ts_info ts_info;
 };
 
+/**
+ * Creates an instance of an interface.
+ * @param name  The device which indentifies this interface.
+ * @return      A pointer to an interface instance on success, NULL otherwise.
+ */
+struct interface *interface_create(const char *name);
+
+/**
+ * Destroys an instance of an interface.
+ * @param iface  A pointer obtained via interface_create().
+ */
+void interface_destroy(struct interface *iface);
+
 /**
  * Ensures that an interface has a proper time stamping label.
  * @param iface  The interface of interest.