嵌入式软件实现应用层和硬件层分层管理

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一、前言

以STM32为例，打开网络上下载的例程或者是购买开发板自带的例程，都会发现应用层中会有stm32f10x.h或者stm32f10x_gpio.h，这些文件严格来时属于硬件层的，如果软件层出现这些文件会显得很乱。

使用过Linux的童鞋们肯定知道linux系统无法直接操作硬件层，打开linux或者rt_thread代码会发现代码中都会有device的源文件，没错，这就是驱动层。

二、实现原理

原理就是将硬件操作的接口全都放到驱动链表上，在驱动层实现device的open、read、write等操作。当然这样做也有弊端，就是驱动find的时候需要遍历一遍驱动链表，这样会增加代码运行时间。

三、代码实现

国际惯例，写代码先写头文件。rt_thread中使用的是双向链表，为了简单在这我只用单向链表。有兴趣的可以自行研究rt_thread

头文件接口:

本次只实现如下接口，device_open ?和device_close等剩下的接口可以自行研究。这样就可以在应用层中只调用如下接口可实现：

/*驱动注册*/int cola_device_register(cola_device_t *dev);?/*驱动查找*/cola_device_t?*cola_device_find(const?char?*name);?/*驱动读*/int cola_device_read(cola_device_t *dev, int pos, void *buffer, int size);?/*驱动写*/int cola_device_write(cola_device_t *dev, int pos, const void *buffer, int size);?/*驱动控制*/int cola_device_ctrl(cola_device_t *dev, int cmd, void *arg);;

头文件cola_device.h：

#ifndef?_COLA_DEVICE_H_#define _COLA_DEVICE_H_?enum?LED_state{  LED_OFF,  LED_ON,  LED_TOGGLE,};?typedef?struct?cola_device?cola_device_t;struct?cola_device_ops{  int??(*init)???(cola_device_t?*dev);  int??(*open)???(cola_device_t?*dev,?int?oflag);  int??(*close)??(cola_device_t?*dev);  int??(*read)???(cola_device_t?*dev,?int?pos,?void?*buffer,?int?size);  int??(*write)??(cola_device_t?*dev,?int?pos,?const?void?*buffer,?int?size);  int??(*control)(cola_device_t?*dev,?int?cmd,?void?*args);};?struct?cola_device{  const?char?*?name;  struct?cola_device_ops?*dops;  struct?cola_device?*next;};?/*驱动注册*/int cola_device_register(cola_device_t *dev);?/*驱动查找*/cola_device_t *cola_device_find(const char *name);?/*驱动读*/int cola_device_read(cola_device_t *dev, int pos, void *buffer, int size);?/*驱动写*/int cola_device_write(cola_device_t *dev, int pos, const void *buffer, int size);?/*驱动控制*/int cola_device_ctrl(cola_device_t *dev, int cmd, void *arg);?#endif

源文件cola_device.c：

#include?"cola_device.h"#include?<string.h>#include <stdbool.h>?struct cola_device *device_list = NULL;?/*查找任务是否存在*/static bool cola_device_is_exists( cola_device_t *dev ){  cola_device_t*?cur?=?device_list;  while(?cur?!=?NULL?)  {    if(?strcmp(cur->name,dev->name)==0)????{????????return?true;????}??????cur?=?cur->next;???}????return?false;??}?static int device_list_inster(cola_device_t *dev){  cola_device_t *cur = device_list;?  if(NULL?==?device_list)  {    device_list?=?dev;    dev->next???=?NULL;  }  else  {    while(NULL?!=?cur->next)    {        cur?=?cur->next;    }?    cur->next?=?dev;    dev->next?=?NULL;  }  return?1;}?/*驱动注册*/int cola_device_register(cola_device_t *dev){  if((NULL?==?dev)?||?(cola_device_is_exists(dev)))  {    return?0;  }  if((NULL?==?dev->name)?||?(NULL?==?dev->dops))  {    return?0;  }  return?device_list_inster(dev);}?/*驱动查找*/cola_device_t?*cola_device_find(const?char?*name){  cola_device_t*?cur?=?device_list;  while(?cur?!=?NULL?)  {    if(?strcmp(cur->name,name)==0)    {      return?cur;    }    cur?=?cur->next;  }  return?NULL;}?/*驱动读*/int cola_device_read(cola_device_t *dev, int pos, void *buffer, int size){  if(dev)  {    if(dev->dops->read)    {      return?dev->dops->read(dev,?pos,?buffer,?size);    }  }  return?0;}?/*驱动写*/int cola_device_write(cola_device_t *dev, int pos, const void *buffer, int size){  if(dev)  {    if(dev->dops->write)    {      return?dev->dops->write(dev,?pos,?buffer,?size);    }  }  return?0;}?/*驱动控制*/int cola_device_ctrl(cola_device_t *dev, int cmd, void *arg){  if(dev)  {    if(dev->dops->control)    {      return?dev->dops->control(dev,?cmd,?arg);    }  }  return?0;}

硬件注册方式：以LED为例，初始化接口void led_register(void)，需要在初始化中调用。

#include?"stm32f0xx.h"#include?"led.h"#include?"cola_device.h"#define?PORT_GREEN_LED?GPIOC??????????????????#define PIN_GREENLED GPIO_Pin_13             ?/*?LED亮、灭、变化?*/#define?LED_GREEN_OFF?(PORT_GREEN_LED->BSRR?=?PIN_GREENLED)#define?LED_GREEN_ON?(PORT_GREEN_LED->BRR??=?PIN_GREENLED)#define LED_GREEN_TOGGLE (PORT_GREEN_LED->ODR ^= PIN_GREENLED)?static cola_device_t led_dev;?static void led_gpio_init(void){  GPIO_InitTypeDef?GPIO_InitStructure;  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOC,?ENABLE);  GPIO_InitStructure.GPIO_Pin?=?PIN_GREENLED;???????????????????????????  GPIO_InitStructure.GPIO_Mode?=?GPIO_Mode_OUT;????????????????????  GPIO_InitStructure.GPIO_Speed?=?GPIO_Speed_50MHz;?????????????????  GPIO_InitStructure.GPIO_OType?=?GPIO_OType_PP;?????????????????????  GPIO_InitStructure.GPIO_PuPd?=?GPIO_PuPd_NOPULL;?????????????????  GPIO_Init(PORT_GREEN_LED,?&GPIO_InitStructure);  LED_GREEN_OFF;}?static int led_ctrl(cola_device_t *dev, int cmd, void *args){  if(LED_TOGGLE?==?cmd)  {    LED_GREEN_TOGGLE;  }  else?{  }  return?1;}?static?struct?cola_device_ops?ops?={  .control?=?led_ctrl,};?void led_register(void){  led_gpio_init();  led_dev.dops?=?&ops;  led_dev.name?=?"led";  cola_device_register(&led_dev);}

应用层app代码:

#include?<string.h>#include?"app.h"#include?"config.h"#include?"cola_device.h"#include "cola_os.h"?static?task_t?timer_500ms;static cola_device_t *app_led_dev;?//led每500ms状态改变一次static void timer_500ms_cb(uint32_t event){  cola_device_ctrl(app_led_dev,LED_TOGGLE,0);}?void app_init(void){  app_led_dev?=?cola_device_find("led");  assert(app_led_dev);  cola_timer_create(&timer_500ms,timer_500ms_cb);  cola_timer_start(&timer_500ms,TIMER_ALWAYS,500);}

这样 app.c 文件中就不需要调用 led.h 头文件了，rtt 就是这样实现的。

四、总结

这样就可以实现软硬件分层了，是不是非常好用！

五、代码下载链接

https://gitee.com/schuck/cola_os