diff --git a/src/libyang.h b/src/libyang.h
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+/**
+ * @file common.h
+ * @author Radek Krejci <rkrejci@cesnet.cz>
+ * @brief common definitions for libyang
+ *
+ * Copyright (c) 2015 CESNET, z.s.p.o.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name of the Company nor the names of its contributors
+ *    may be used to endorse or promote products derived from this
+ *    software without specific prior written permission.
+ */
+
+#ifndef LY_LIBYANG_H_
+#define LY_LIBYANG_H_
+
+/**
+ * @page howto How To ...
+ *
+ * - @subpage howtologger
+ */
+
+/**
+ * @defgroup logger libyang logger
+ *
+ * @page howtologger Logger
+ *
+ * There are 4 verbosity levels defined as ::LY_VERB_LEVEL. The level can be
+ * changed by the ly_verbosity() function. By default, the verbosity level is
+ * set to #LY_VERB_ERR value;
+ *
+ */
+
+/**
+ * @typedef LY_VERB_LEVEL
+ * @brief Verbosity levels.
+ * @ingroup logger
+ */
+typedef enum {
+	LY_VERB_ERR,  /**< Print only error messages. */
+	LY_VERB_WRN,  /**< Print error and warning messages. */
+	LY_VERB_VRB,  /**< Besides errors and warnings, print some other verbose messages. */
+	LY_VERB_DBG   /**< Print all messages including some development debug messages. */
+} LY_VERB_LEVEL;
+
+/**
+ *
+ */
+void ly_verbosity(LY_VERB_LEVEL level);
+
+
+#endif /* LY_LIBYANG_H_ */