添加rtthread相关代码

riscv/rtthread/components/drivers/misc/rt_null.c

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2011-2023, Shanghai Real-Thread Electronic Technology Co.,Ltd
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2020-12-03     quanzhao     the first version
+ */
+
+#include <time.h>
+#include <string.h>
+#include <rtthread.h>
+
+static struct rt_device null_dev;
+
+static rt_ssize_t null_read    (rt_device_t dev, rt_off_t pos, void *buffer, rt_size_t size)
+{
+    return 0;
+}
+
+static rt_ssize_t null_write   (rt_device_t dev, rt_off_t pos, const void *buffer, rt_size_t size)
+{
+    return size;
+}
+
+static rt_err_t  null_control (rt_device_t dev, int cmd, void *args)
+{
+    return RT_EOK;
+}
+
+#ifdef RT_USING_DEVICE_OPS
+const static struct rt_device_ops null_ops =
+{
+    RT_NULL,
+    RT_NULL,
+    RT_NULL,
+    null_read,
+    null_write,
+    null_control
+};
+#endif
+
+int null_device_init(void)
+{
+    static rt_bool_t init_ok = RT_FALSE;
+
+    if (init_ok)
+    {
+        return 0;
+    }
+    RT_ASSERT(!rt_device_find("null"));
+    null_dev.type    = RT_Device_Class_Miscellaneous;
+
+#ifdef RT_USING_DEVICE_OPS
+    null_dev.ops     = &null_ops;
+#else
+    null_dev.init    = RT_NULL;
+    null_dev.open    = RT_NULL;
+    null_dev.close   = RT_NULL;
+    null_dev.read    = null_read;
+    null_dev.write   = null_write;
+    null_dev.control = null_control;
+#endif
+
+    /* no private */
+    null_dev.user_data = RT_NULL;
+
+    rt_device_register(&null_dev, "null", RT_DEVICE_FLAG_RDWR);
+
+    init_ok = RT_TRUE;
+
+    return 0;
+}
+INIT_DEVICE_EXPORT(null_device_init);
+