!114 添加虚拟设备 zero ，并修复 null 设备的读操作错误实现。

Merge pull request !114 from qz-lab/add-device-zero

components/drivers/Kconfig

@@ -123,6 +123,10 @@ config RT_USING_NULL
     bool "Using NULL device drivers"
     default n
 
+config RT_USING_ZERO
+    bool "Using ZERO device drivers"
+    default n
+
 config RT_USING_RANDOM
     bool "Using RANDOM device drivers"
     default n

components/drivers/misc/SConscript

@@ -26,6 +26,9 @@ if GetDepend(['RT_USING_INPUT_CAPTURE']):
 if GetDepend(['RT_USING_NULL']):
     src = src + ['rt_null.c']
 
+if GetDepend(['RT_USING_ZERO']):
+    src = src + ['rt_zero.c']
+
 if GetDepend(['RT_USING_RANDOM']):
     src = src + ['rt_random.c']
 

components/drivers/misc/rt_null.c

@@ -14,8 +14,7 @@ static struct rt_device null_dev;
 
 static rt_size_t null_read    (rt_device_t dev, rt_off_t pos, void *buffer, rt_size_t size)
 {
-    rt_memset(buffer, 0, size);
-    return size;
+    return 0;
 }
 
 static rt_size_t null_write   (rt_device_t dev, rt_off_t pos, const void *buffer, rt_size_t size)

components/drivers/misc/rt_zero.c

@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2011-2020, 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 zero_dev;
+
+static rt_size_t zero_read    (rt_device_t dev, rt_off_t pos, void *buffer, rt_size_t size)
+{
+    rt_memset(buffer, 0, size);
+    return size;
+}
+
+static rt_size_t zero_write   (rt_device_t dev, rt_off_t pos, const void *buffer, rt_size_t size)
+{
+    return size;
+}
+
+static rt_err_t  zero_control (rt_device_t dev, int cmd, void *args)
+{
+    return RT_EOK;
+}
+
+#ifdef RT_USING_DEVICE_OPS
+const static struct rt_device_ops zero_ops =
+{
+    RT_NULL,
+    RT_NULL,
+    RT_NULL,
+    zero_read,
+    zero_write,
+    zero_control
+};
+#endif
+
+int zero_device_init(void)
+{
+    static rt_bool_t init_ok = RT_FALSE;
+
+    if (init_ok)
+    {
+        return 0;
+    }
+    RT_ASSERT(!rt_device_find("zero"));
+    zero_dev.type    = RT_Device_Class_Miscellaneous;
+
+#ifdef RT_USING_DEVICE_OPS
+    zero_dev.ops     = &zero_ops;
+#else
+    zero_dev.init    = RT_NULL;
+    zero_dev.open    = RT_NULL;
+    zero_dev.close   = RT_NULL;
+    zero_dev.read    = zero_read;
+    zero_dev.write   = zero_write;
+    zero_dev.control = zero_control;
+#endif
+
+    /* no private */
+    zero_dev.user_data = RT_NULL;
+
+    rt_device_register(&zero_dev, "zero", RT_DEVICE_FLAG_RDWR);
+
+    init_ok = RT_TRUE;
+
+    return 0;
+}
+INIT_DEVICE_EXPORT(zero_device_init);
+