drivers/periph: define periph_rtc_mem

drivers/include/periph/rtc_mem.h

@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2021 ML!PA Consulting GmbH
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser General
+ * Public License v2.1. See the file LICENSE in the top level directory for more
+ * details.
+ */
+
+/**
+ * @defgroup    drivers_periph_rtc_mem Low-Power RTC Memory
+ * @ingroup     drivers_periph_rtc
+ * @brief       Low-level RTC Memory peripheral driver
+ *
+ * This API provides an interface to access low-power memory present on some RTCs.
+ * This memory is retained even when the rest of the system is powered off.
+ *
+ * @{
+ * @file
+ * @brief       Low-level RTC memory peripheral driver interface definitions
+ *
+ * @author      Benjamin Valentin <benjamin.valentin@ml-pa.com>
+ */
+
+#ifndef PERIPH_RTC_MEM_H
+#define PERIPH_RTC_MEM_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   Get the amount of RTC memory.
+ *
+ * @return  The usable amount of RTC memory in bytes
+ */
+size_t rtc_mem_size(void);
+
+/**
+ * @brief Read from RTC memory
+ *
+ * @note  Reading beyond @ref rtc_mem_size are illegal and trigger an
+ *        assertion / be discarded.
+ *
+ * @param[in]  offset   Offset to the start of RTC memory in bytes
+ * @param[out] data     Destination buffer
+ * @param[in]  len      Amount of bytes to read
+ */
+void rtc_mem_read(unsigned offset, void *data, size_t len);
+
+/**
+ * @brief Write to RTC memory
+ *
+ * @note  Writing beyond @ref rtc_mem_size are illegal and trigger an
+ *        assertion / be discarded.
+ *
+ * @param[in] offset    Offset to the start of RTC memory in bytes
+ * @param[in] data      Source buffer
+ * @param[in] len       Amount of bytes to write
+ */
+void rtc_mem_write(unsigned offset, const void *data, size_t len);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* PERIPH_RTC_MEM_H */
+/** @} */

kconfigs/Kconfig.features

@@ -257,6 +257,11 @@ config HAS_PERIPH_RTC
     help
         Indicates that an RTC peripheral is present.
 
+config HAS_PERIPH_RTC_MEM
+    bool
+    help
+        Indicates that the RTC peripheral provides storage memory for deep sleep.
+
 config HAS_PERIPH_RTC_MS
     bool
     help