Helper functions for sharing hardware peripherals on NRF52

Common functions for getting and setting the instance owner of a
hardware peripheral. Used for reconfiguring SPI/I2C after change
of ownership.

targets/TARGET_NORDIC/TARGET_NRF5x/object_owners.c

@@ -0,0 +1,57 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2018 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "object_owners.h"
+
+#include "nrf.h"
+#include "nrf_peripherals.h"
+
+#include <stdio.h>
+
+#define SPI2C_INSTANCES SPI_COUNT
+
+static void * nordic_spi2c_owners[SPI2C_INSTANCES] = { NULL, NULL, NULL };
+
+/**
+ * Brief       Set instance owner for the SPI/I2C peripheral.
+ *
+ * Parameter   instance  The instance.
+ * Parameter   object    The object.
+ */
+void object_owner_spi2c_set(int instance, void *object)
+{
+    if (instance < SPI2C_INSTANCES) {
+        nordic_spi2c_owners[instance] = object;
+    }
+}
+
+/**
+ * Brief       Get instance owner for the SPI/I2C peripheral.
+ *
+ * Parameter   instance  The instance.
+ *
+ * Return      Pointer to the object owning the instance.
+ */
+void * object_owner_spi2c_get(int instance)
+{
+    void *object = (void *) 0xFFFFFFFF;
+
+    if (instance < SPI2C_INSTANCES) {
+        object = nordic_spi2c_owners[instance];
+    }
+
+    return object;
+}

targets/TARGET_NORDIC/TARGET_NRF5x/object_owners.h

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+/* mbed Microcontroller Library
+ * Copyright (c) 2018 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef OBJECT_OWNERS_H
+#define OBJECT_OWNERS_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief      Set instance owner for the SPI/I2C peripheral.
+ *
+ * @param[in]  instance  The instance.
+ * @param      object    The object.
+ */
+void object_owner_spi2c_set(int instance, void *object);
+
+/**
+ * @brief      Get instance owner for the SPI/I2C peripheral.
+ *
+ * @param[in]  instance  The instance.
+ *
+ * @return     Pointer to the object owning the instance.
+ */
+void * object_owner_spi2c_get(int instance);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif