add device check in register function, which is provided by Rob <rdent@iinet.net.au>.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2355 bbd45198-f89e-11dd-88c7-29a3b14d5316

src/device.c

@@ -11,6 +11,8 @@
  * Date           Author       Notes
  * 2007-01-21     Bernard      the first version
  * 2010-05-04     Bernard      add rt_device_init implementation
+ * 2012-10-20     Bernard      add device check in register function, 
+ *                             provided by Rob <rdent@iinet.net.au>
  */
 
 #include <rtthread.h>
@@ -31,6 +33,9 @@ rt_err_t rt_device_register(rt_device_t dev, const char *name, rt_uint16_t flags
 	if (dev == RT_NULL)
 		return -RT_ERROR;
 
+	if (rt_device_find(name) != RT_NULL) 
+		return -RT_ERROR;
+
 	rt_object_init(&(dev->parent), RT_Object_Class_Device, name);
 	dev->flag = flags;
 
@@ -197,6 +202,8 @@ rt_err_t rt_device_open(rt_device_t dev, rt_uint16_t oflag)
 
 	/* if device is not initialized, initialize it. */
 	if (!(dev->flag & RT_DEVICE_FLAG_ACTIVATED))
+	{
+		if (dev->init != RT_NULL )
 		{
 			result = dev->init(dev);
 			if (result != RT_EOK)
@@ -206,10 +213,9 @@ rt_err_t rt_device_open(rt_device_t dev, rt_uint16_t oflag)
 
 				return result;
 			}
-		else
-		{
-			dev->flag |= RT_DEVICE_FLAG_ACTIVATED;
 		}
+
+		dev->flag |= RT_DEVICE_FLAG_ACTIVATED;
 	}
 
 	/* device is a stand alone device and opened */
@@ -225,7 +231,7 @@ rt_err_t rt_device_open(rt_device_t dev, rt_uint16_t oflag)
 	else
 	{
 		/* no this interface in device driver */
-		result = -RT_ENOSYS;
+		/* result = -RT_ENOSYS; not set errno */
 	}
 
 	/* set open flag */
@@ -259,7 +265,7 @@ rt_err_t rt_device_close(rt_device_t dev)
 	else
 	{
 		/* no this interface in device driver */
-		result = -RT_ENOSYS;
+		/* result = -RT_ENOSYS; not set errno */
 	}
 
 	/* set open flag */