RTThreadIO设备管理模型

转《 RT-Thread IO设备管理模型》： https://zhuanlan.zhihu.com/p/339096988

RT-Thread的IO设备管理模型框架位于硬件层和应用程序之间，包括设备驱动层、驱动框架层和IO设备管理层，向上层层抽象，目标是针对各种不同的IO设备提供给应用程序相同的接口。这样就可以减小底层与应用层的耦合，底层变动不影响应用程序。这里介绍IO设备管理层，即抽象出的提供给应用程序的统一接口。

驱动方法包括：

1. 设备控制块

在RT-Thread中，设备也是一种内核对象，由rt_object继承而来，会被纳入对象管理。在对象容器中，会维护一个设备链表。

/* include/rtdef.h *//*** Device structure*/
struct rt_device
{struct rt_object parent; /**#else/* common device interface */rt_err_t (*init) (rt_device_t dev);rt_err_t (*open) (rt_device_t dev, rt_uint16_t oflag);rt_err_t (*close) (rt_device_t dev);rt_size_t (*read) (rt_device_t dev, rt_off_t pos, void *buffer, rt_size_t size);rt_size_t (*write) (rt_device_t dev, rt_off_t pos, const void *buffer, rt_size_t size);rt_err_t (*control)(rt_device_t dev, int cmd, void *args);
#endif#if defined(RT_USING_POSIX)const struct dfs_file_ops *fops;struct rt_wqueue wait_queue;
#endifvoid *user_data; /**};

• parent：基类内核对象
• type：设备类型，可以有如下取值

/* include/rtdef.h *//*** device (I/O) class type*/
enum rt_device_class_type
{RT_Device_Class_Char = 0, /**};

• flag：设备标志
• open_flag：设备打开标志
• ref_count：设备被引用次数
• device_id：设备ID
• rx_indicate, tx_complete：设备接收和发送回调函数
• ops或者init、open、close、read、write、control：设备操作方法
• fops, wait_queue：设备的POSIX接口
• user_data：设备私有数据

2. 设备操作

2.1 创建设备rt_device_create

从内存堆中创建设备对象并进行初始化。

/* src/device.c *//*** This function creates a device object with user data size.** @param type, the kind type of this device object.* @param attach_size, the size of user data.** @return the allocated device object, or RT_NULL when failed.*/
rt_device_t rt_device_create(int type, int attach_size)
{int size;rt_device_t device;size = RT_ALIGN(sizeof(struct rt_device), RT_ALIGN_SIZE);attach_size = RT_ALIGN(attach_size, RT_ALIGN_SIZE);/* use the total size */size += attach_size;device = (rt_device_t)rt_malloc(size);if (device){rt_memset(device, 0x0, sizeof(struct rt_device));device->type = (enum rt_device_class_type)type;}return device;
}
RTM_EXPORT(rt_device_create);

备注：

关于：RT_ALIGN   

这个宏的功能是整数提升，即将size提升为align定义的整数的倍数。

例如：  align=8,size=7，则这条宏运行的结果是8；

            align=8,size=13，则这条宏运行的结果是16。

该函数作用是按照设备控制块和用户data的大小分配内存，分配的大小不能简单的按照所占用的字节数算，要对齐后取整计算。

完成的主要工作：

• 给设备对象分配内存空间
• 设置设备类型，其他成员清0

2.2 销毁设备rt_device_destroy

销毁动态创建的设备对象

/* src/device.c *//*** This function destroy the specific device object.** @param dev, the specific device object.*/
void rt_device_destroy(rt_device_t dev)
{RT_ASSERT(dev != RT_NULL);RT_ASSERT(rt_object_get_type(&dev->parent) == RT_Object_Class_Device);RT_ASSERT(rt_object_is_systemobject(&dev->parent) == RT_FALSE);rt_object_detach(&(dev->parent));/* release this device object */rt_free(dev);
}
RTM_EXPORT(rt_device_destroy);

完成的主要工作：

• 设备类型清0，从对象容器中移除
• 释放设备对象空间

2.3 注册设备rt_device_register

无论是静态设备还是动态设备，都需要注册到IO设备管理框架中，才能被应用程序使用。

/* src/device.c *//*** This function registers a device driver with specified name.** @param dev the pointer of device driver structure* @param name the device driver&＃39;s name* @param flags the capabilities flag of device** @return the error code, RT_EOK on initialization successfully.*/
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;dev->ref_count = 0;dev->open_flag = 0;#if defined(RT_USING_POSIX)dev->fops = RT_NULL;rt_wqueue_init(&(dev->wait_queue));
#endifreturn RT_EOK;
}
RTM_EXPORT(rt_device_register);

完成的主要工作：

• 首先用rt_device_find查找设备名是否已被注册过，如果已注册过，则返回错误（rt_device_find后面介绍）
• 初始化基类对象，纳入对象容器
• 设置设备标志，被引用次数和打开标志清0

2.4 注销设备rt_device_register

将设备从IO设备管理框架中移除，应用程序不再能够访问

/* src/device.c *//*** This function removes a previously registered device driver** @param dev the pointer of device driver structure** @return the error code, RT_EOK on successfully.*/
rt_err_t rt_device_unregister(rt_device_t dev)
{RT_ASSERT(dev != RT_NULL);RT_ASSERT(rt_object_get_type(&dev->parent) == RT_Object_Class_Device);RT_ASSERT(rt_object_is_systemobject(&dev->parent));rt_object_detach(&(dev->parent));return RT_EOK;
}
RTM_EXPORT(rt_device_unregister);

完成的主要工作：

• 设备类型清0，从对象容器中移除

2.5 查找设备rt_device_find

把设备注册到管理框架中后，应用层要访问设备，需要先通过设备名查找对应的设备驱动。

/* src/device.c *//*** This function finds a device driver by specified name.** @param name the device driver&＃39;s name** @return the registered device driver on successful, or RT_NULL on failure.*/
rt_device_t rt_device_find(const char *name)
{struct rt_object *object;struct rt_list_node *node;struct rt_object_information *information;/* enter critical */if (rt_thread_self() != RT_NULL)rt_enter_critical();/* try to find device object */information = rt_object_get_information(RT_Object_Class_Device);RT_ASSERT(information != RT_NULL);for (node = information->object_list.next;node != &(information->object_list);node = node->next){object = rt_list_entry(node, struct rt_object, list);if (rt_strncmp(object->name, name, RT_NAME_MAX) == 0){/* leave critical */if (rt_thread_self() != RT_NULL)rt_exit_critical();return (rt_device_t)object;}}/* leave critical */if (rt_thread_self() != RT_NULL)rt_exit_critical();/* not found */return RT_NULL;
}
RTM_EXPORT(rt_device_find);

完成的主要工作：

• 在对象容器的设备链表中查找指定名字的设备，如果找到就返回设备句柄，否则返回RT_NULL

2.6 初始化设备rt_device_init

/* src/device.c *//*** This function will initialize the specified device** @param dev the pointer of device driver structure** @return the result*/
rt_err_t rt_device_init(rt_device_t dev)
{rt_err_t result = RT_EOK;RT_ASSERT(dev != RT_NULL);/* get device_init handler */if (device_init != RT_NULL){if (!(dev->flag & RT_DEVICE_FLAG_ACTIVATED)){result = device_init(dev);if (result != RT_EOK){rt_kprintf("To initialize device:%s failed. The error code is %d\n",dev->parent.name, result);}else{dev->flag |= RT_DEVICE_FLAG_ACTIVATED;}}}return result;
}

完成的主要工作：

• 在设备是未激活状态时，调用设备对象的init方法进行初始化，init方法需要底层实现，初始化成功后设备改为激活状态

注：通过激活状态的判断，可以避免重复初始化。
代码中的device_init是一个宏定义

/* src/device.c */#ifdef RT_USING_DEVICE_OPS
#define device_init (dev->ops->init)
#define device_open (dev->ops->open)
#define device_close (dev->ops->close)
#define device_read (dev->ops->read)
#define device_write (dev->ops->write)
#define device_control (dev->ops->control)
#else
#define device_init (dev->init)
#define device_open (dev->open)
#define device_close (dev->close)
#define device_read (dev->read)
#define device_write (dev->write)
#define device_control (dev->control)
#endif

可见就是调用设备相应的操作方法。

2.7 打开设备rt_device_open

/* src/device.c *//*** This function will open a device** @param dev the pointer of device driver structure* @param oflag the flags for device open** @return the result*/
rt_err_t rt_device_open(rt_device_t dev, rt_uint16_t oflag)
{rt_err_t result = RT_EOK;RT_ASSERT(dev != RT_NULL);RT_ASSERT(rt_object_get_type(&dev->parent) == RT_Object_Class_Device);/* if device is not initialized, initialize it. */if (!(dev->flag & RT_DEVICE_FLAG_ACTIVATED)){if (device_init != RT_NULL){result = device_init(dev);if (result != RT_EOK){rt_kprintf("To initialize device:%s failed. The error code is %d\n",dev->parent.name, result);return result;}}dev->flag |= RT_DEVICE_FLAG_ACTIVATED;}/* device is a stand alone device and opened */if ((dev->flag & RT_DEVICE_FLAG_STANDALONE) &&(dev->open_flag & RT_DEVICE_OFLAG_OPEN)){return -RT_EBUSY;}/* call device_open interface */if (device_open != RT_NULL){result = device_open(dev, oflag);}else{/* set open flag */dev->open_flag = (oflag & RT_DEVICE_OFLAG_MASK);}/* set open flag */if (result == RT_EOK || result == -RT_ENOSYS){dev->open_flag |= RT_DEVICE_OFLAG_OPEN;dev->ref_count++;/* don&＃39;t let bad things happen silently. If you are bitten by this assert,* please set the ref_count to a bigger type. */RT_ASSERT(dev->ref_count != 0);}return result;
}
RTM_EXPORT(rt_device_open);

完成的主要工作：

• 通过设备激活标志判断是否已经初始化，如果未激活则先进行初始化
• 如果设备是standalone并且已打开，直接返回-RT_EBUSY
• 调用设备对象的open方法，open方法需要底层实现，如果打开成功设置open_flag，被引用次数ref_count加1

2.8 关闭设备rt_device_close

/* src/device.c *//*** This function will close a device** @param dev the pointer of device driver structure** @return the result*/
rt_err_t rt_device_close(rt_device_t dev)
{rt_err_t result = RT_EOK;RT_ASSERT(dev != RT_NULL);RT_ASSERT(rt_object_get_type(&dev->parent) == RT_Object_Class_Device);if (dev->ref_count == 0)return -RT_ERROR;dev->ref_count--;if (dev->ref_count != 0)return RT_EOK;/* call device_close interface */if (device_close != RT_NULL){result = device_close(dev);}/* set open flag */if (result == RT_EOK || result == -RT_ENOSYS)dev->open_flag = RT_DEVICE_OFLAG_CLOSE;return result;
}
RTM_EXPORT(rt_device_close);

完成的主要工作：

• 设备被引用次数减1
• 如果仍然不为0，则直接返回
• 如果已经减到0，则调用设备的close方法，close需要底层实现；如果关闭成功，设置关闭标志

2.9 控制设备rt_device_control

/* src/device.c *//*** This function will perform a variety of control functions on devices.** @param dev the pointer of device driver structure* @param cmd the command sent to device* @param arg the argument of command** @return the result*/
rt_err_t rt_device_control(rt_device_t dev, int cmd, void *arg)
{RT_ASSERT(dev != RT_NULL);RT_ASSERT(rt_object_get_type(&dev->parent) == RT_Object_Class_Device);/* call device_write interface */if (device_control != RT_NULL){return device_control(dev, cmd, arg);}return -RT_ENOSYS;
}
RTM_EXPORT(rt_device_control);

完成的主要工作：

• 调用设备的control方法，control需要底层实现

2.10 读设备rt_device_read

/* src/device.c *//*** This function will read some data from a device.** @param dev the pointer of device driver structure* @param pos the position of reading* @param buffer the data buffer to save read data* @param size the size of buffer** @return the actually read size on successful, otherwise negative returned.** @note since 0.4.0, the unit of size/pos is a block for block device.*/
rt_size_t rt_device_read(rt_device_t dev,rt_off_t pos,void *buffer,rt_size_t size)
{RT_ASSERT(dev != RT_NULL);RT_ASSERT(rt_object_get_type(&dev->parent) == RT_Object_Class_Device);if (dev->ref_count == 0){rt_set_errno(-RT_ERROR);return 0;}/* call device_read interface */if (device_read != RT_NULL){return device_read(dev, pos, buffer, size);}/* set error code */rt_set_errno(-RT_ENOSYS);return 0;
}
RTM_EXPORT(rt_device_read);

完成的主要工作：

• 如果设备还没有打开，设置错误标志后返回
• 否则调用设备的read方法，read方法需要底层实现

2.11 写设备rt_device_write

/* src/device.c *//*** This function will write some data to a device.** @param dev the pointer of device driver structure* @param pos the position of written* @param buffer the data buffer to be written to device* @param size the size of buffer** @return the actually written size on successful, otherwise negative returned.** @note since 0.4.0, the unit of size/pos is a block for block device.*/
rt_size_t rt_device_write(rt_device_t dev,rt_off_t pos,const void *buffer,rt_size_t size)
{RT_ASSERT(dev != RT_NULL);RT_ASSERT(rt_object_get_type(&dev->parent) == RT_Object_Class_Device);if (dev->ref_count == 0){rt_set_errno(-RT_ERROR);return 0;}/* call device_write interface */if (device_write != RT_NULL){return device_write(dev, pos, buffer, size);}/* set error code */rt_set_errno(-RT_ENOSYS);return 0;
}
RTM_EXPORT(rt_device_write);

完成的主要工作：

• 如果设备还没有打开，设置错误标志后返回
• 否则调用设备的write方法，write方法需要底层实现

综上可见，rt_device_init、rt_device_control、rt_device_open、rt_device_close、rt_device_read和rt_device_write就是对设备相应底层驱动的封装调用，要真正实现设备操作重点是要实现这些底层函数。

2.12 设置数据接收回调rt_device_set_rx_indicate

设备收到数据后会在设备驱动框架层调用设置的回调函数

/* src/device.c *//*** This function will set the reception indication callback function. This callback function* is invoked when this device receives data.** @param dev the pointer of device driver structure* @param rx_ind the indication callback function** @return RT_EOK*/
rt_err_t
rt_device_set_rx_indicate(rt_device_t dev,rt_err_t (*rx_ind)(rt_device_t dev, rt_size_t size))
{RT_ASSERT(dev != RT_NULL);RT_ASSERT(rt_object_get_type(&dev->parent) == RT_Object_Class_Device);dev->rx_indicate = rx_ind;return RT_EOK;
}
RTM_EXPORT(rt_device_set_rx_indicate);

完成的主要工作：

• 设置设备的rx_indicate成员

2.13 设置数据发送回调rt_device_set_tx_complete

设备发送完数据后在设备驱动框架层调用设置的回调函数

/* src/device.c *//*** This function will set the indication callback function when device has* written data to physical hardware.** @param dev the pointer of device driver structure* @param tx_done the indication callback function** @return RT_EOK*/
rt_err_t
rt_device_set_tx_complete(rt_device_t dev,rt_err_t (*tx_done)(rt_device_t dev, void *buffer))
{RT_ASSERT(dev != RT_NULL);RT_ASSERT(rt_object_get_type(&dev->parent) == RT_Object_Class_Device);dev->tx_complete = tx_done;return RT_EOK;
}
RTM_EXPORT(rt_device_set_tx_complete);

完成的主要工作：

• 设置设备的tx_complete成员