diff --git a/configure.ac b/configure.ac
index c6c23fd..35f4c17 100644
--- a/configure.ac
+++ b/configure.ac
@@ -33,6 +33,7 @@ AC_PATH_PROG(PKG_CONFIG, pkg-config)
 AC_HEADER_STDC
 AC_HEADER_STDBOOL
 AC_CHECK_HEADERS([stdio.h stdlib.h stdint.h stddef.h stdbool.h])
+AC_CHECK_FUNCS(strdup, [AC_DEFINE([_XOPEN_SOURCE], [600], [Enable POSIX extensions if present])])
 
 # Checks for types
 AC_TYPE_SIZE_T
@@ -186,20 +187,11 @@ fi
 
 AC_SUBST(PKG_CONFIG_REQUIRES)
 
-# Set C standard to C99
-# C99 standard support (default: yes)
-AC_ARG_ENABLE([std-c99],AS_HELP_STRING([--disable-std-c99],[Disable C99 standard when compiling]),[enable_std_c99=$enableval],[enable_std_c99="yes"])
- 
-AC_MSG_CHECKING(for C99 support)
-AC_MSG_RESULT($enable_std_c99)
- 
-if test x"$enable_std_c99" != "xno"
-then
-	CFLAGS="$CFLAGS -std=c99"
+# Defines and C flags
+CFLAGS="$CFLAGS -std=c99"
 
-	# Workarounds for libusb in c99
-	CFLAGS="$CFLAGS -Du_int8_t=uint8_t -Du_int16_t=uint16_t"
-fi
+# Workarounds for libusb in c99
+CFLAGS="$CFLAGS -Du_int8_t=uint8_t -Du_int16_t=uint16_t"
 
 AC_CONFIG_FILES([
 		Makefile
diff --git a/src/lib/drivers.h b/src/lib/drivers.h
index 6d63165..8a04ec6 100644
--- a/src/lib/drivers.h
+++ b/src/lib/drivers.h
@@ -1,4 +1,4 @@
-/**
+/*-
  * Public platform independent Near Field Communication (NFC) library
  * 
  * Copyright (C) 2009, Roel Verdult
@@ -15,15 +15,21 @@
  *
  * You should have received a copy of the GNU Lesser General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>
- * 
- * 
+ */
+
+/**
  * @file drivers.h
- * @brief
+ * @brief Supported drivers header
  */
 
 #ifndef __NFC_DRIVERS_H__
 #define __NFC_DRIVERS_H__
 
+#ifdef HAVE_CONFIG_H
+  #include "config.h"
+#endif /* HAVE_CONFIG_H */
+
+
 #include <nfc/nfc-types.h>
 
 #ifdef HAVE_PCSC_LITE
diff --git a/src/lib/drivers/arygon.c b/src/lib/drivers/arygon.c
index 2722e78..788489b 100644
--- a/src/lib/drivers/arygon.c
+++ b/src/lib/drivers/arygon.c
@@ -1,4 +1,4 @@
-/**
+/*-
  * Public platform independent Near Field Communication (NFC) library
  * 
  * Copyright (C) 2009, Roel Verdult
@@ -15,20 +15,24 @@
  *
  * You should have received a copy of the GNU Lesser General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>
- * 
- * 
- * @file arygon.c
- * @brief
  */
-#define _XOPEN_SOURCE 500
+
+/**
+ * @file arygon.c
+ * @brief ARYGON readers driver
+ * 
+ * This driver can handle ARYGON readers that use UART as bus.
+ * UART connection can be direct (host<->arygon_uc) or could be provided by internal USB to serial interface (e.g. host<->ftdi_chip<->arygon_uc)
+ */
+#include "../drivers.h"
+#include "../bitutils.h"
+
 #include <stdio.h>
 
 #include "arygon.h"
 
 #include <nfc/nfc-messages.h>
 
-#include "../drivers.h"
-#include "../bitutils.h"
 // Bus
 #include "../buses/uart.h"
 
diff --git a/src/lib/drivers/pn532_uart.c b/src/lib/drivers/pn532_uart.c
index f18e40f..2d056af 100644
--- a/src/lib/drivers/pn532_uart.c
+++ b/src/lib/drivers/pn532_uart.c
@@ -1,4 +1,4 @@
-/**
+/*-
  * Public platform independent Near Field Communication (NFC) library
  * 
  * Copyright (C) 2009, Roel Verdult
@@ -15,12 +15,15 @@
  *
  * You should have received a copy of the GNU Lesser General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>
- * 
- * 
- * @file pn532_uart.c
- * @brief
  */
-#define _XOPEN_SOURCE 600
+
+/**
+ * @file pn532_uart.c
+ * @brief PN532 driver using UART bus (UART, RS232, etc.)
+ */
+#include "../drivers.h"
+#include "../bitutils.h"
+
 #include <stdio.h>
 #include <string.h>
 
@@ -28,8 +31,6 @@
 
 #include <nfc/nfc-messages.h>
 
-#include "../drivers.h"
-#include "../bitutils.h"
 
 // Bus
 #include "uart.h"