ulp-riscv: added lock API to provide mutual exclusion when sharing variables between the main CPU and the ULP.

components/ulp/ulp_riscv/shared/include/ulp_riscv_lock_shared.h

@@ -0,0 +1,35 @@
+/*
+ * SPDX-FileCopyrightText: 2022 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#pragma once
+
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Enum representing which processor is allowed to enter the critical section
+ *
+ */
+typedef enum {
+    ULP_RISCV_LOCK_TURN_ULP,        /*!< ULP's turn to enter the critical section */
+    ULP_RISCV_LOCK_TURN_MAIN_CPU,   /*!< Main CPU's turn to enter the critical section */
+} ulp_riscv_lock_turn_t;
+
+/**
+ * @brief Structure representing a lock shared between ULP and main CPU
+ *
+ */
+typedef struct {
+    volatile bool critical_section_flag_ulp;        /*!<  ULP wants to enter the critical sections */
+    volatile bool critical_section_flag_main_cpu;   /*!<  Main CPU wants to enter the critical sections */
+    volatile ulp_riscv_lock_turn_t turn;            /*!<  Which CPU is allowed to enter the critical section */
+} ulp_riscv_lock_t;
+
+#ifdef __cplusplus
+}
+#endif