stm32f4:rng: basic functions with documentation.

Reviewed-by: Karl Palsson <karlp@tweak.net.au>
Removed higher level helpers from this commit, they are not a very
friendly API to use.

include/libopencm3/stm32/common/rng_common_f24.h

@@ -1,3 +1,5 @@
+/** @addtogroup rng_file
+ */
 /*
  * This file is part of the libopencm3 project.
  *
@@ -26,6 +28,8 @@ specific memorymap.h header before including this header file.*/
 #ifndef LIBOPENCM3_RNG_COMMON_F24_H
 #define LIBOPENCM3_RNG_COMMON_F24_H
 
+/**@{*/
+
 /* --- Random number generator registers ----------------------------------- */
 
 /* Control register */
@@ -62,6 +66,17 @@ specific memorymap.h header before including this header file.*/
 /* Seed error interrupt status */
 #define RNG_SR_SEIS		(1 << 6)
 
+/* --- Function prototypes ------------------------------------------------- */
+
+BEGIN_DECLS
+
+void rng_enable(void);
+void rng_disable(void);
+
+END_DECLS
+
+/**@}*/
+
 #endif
 /** @cond */
 #else

include/libopencm3/stm32/rng.h

@@ -0,0 +1,27 @@
+/* This provides unification of code over STM32 subfamilies */
+
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <libopencm3/cm3/common.h>
+#include <libopencm3/stm32/memorymap.h>
+
+#if defined(STM32F4)
+#       include <libopencm3/stm32/f4/rng.h>
+#else
+#       error "stm32 family not defined."
+#endif