一、前言

以STM32為例，打開網絡上下載的例程或者是購買開發板自帶的例程，都會發現應用層中會有stm32f10x.h或者stm32f10x_gpio.h，這些文件嚴格來時屬于硬件層的，如果軟件層出現這些文件會顯得很亂。

使用過Linux的童鞋們肯定知道linux系統無法直接操作硬件層，打開linux或者rt_thread代碼會發現代碼中都會有device的源文件，沒錯，這就是驅動層。

二、實現原理

原理就是將硬件操作的接口全都放到驅動鏈表上，在驅動層實現device的open、read、write等操作。當然這樣做也有弊端，就是驅動find的時候需要遍歷一遍驅動鏈表，這樣會增加代碼運行時間。

三、代碼實現

國際慣例，寫代碼先寫頭文件。rt_thread中使用的是雙向鏈表，為了簡單在這我只用單向鏈表。有興趣的可以自行研究rt_thread

頭文件接口:

本次只實現如下接口，device_open ?和device_close等剩下的接口可以自行研究。這樣就可以在應用層中只調用如下接口可實現：

/*
驅動注冊
*/
int cola_device_register(cola_device_t *dev);


/*
驅動查找
*/
cola_device_t?*cola_device_find(const?char?*name);


/*
驅動讀
*/
int cola_device_read(cola_device_t *dev, int pos, void *buffer, int size);


/*
驅動寫
*/
int cola_device_write(cola_device_t *dev, int pos, const void *buffer, int size);


/*
驅動控制
*/
int cola_device_ctrl(cola_device_t *dev, int cmd, void *arg);;

頭文件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;
};


/*
驅動注冊
*/
int cola_device_register(cola_device_t *dev);


/*
驅動查找
*/
cola_device_t *cola_device_find(const char *name);


/*
驅動讀
*/
int cola_device_read(cola_device_t *dev, int pos, void *buffer, int size);


/*
驅動寫
*/
int cola_device_write(cola_device_t *dev, int pos, const void *buffer, int size);


/*
驅動控制
*/
int cola_device_ctrl(cola_device_t *dev, int cmd, void *arg);


#endif

源文件cola_device.c：

#include?"cola_device.h"
#include?
#include 

struct cola_device *device_list = NULL;

/*
查找任務是否存在
*/
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;
}


/*
驅動注冊
*/
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);
}


/*
驅動查找
*/
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;
}


/*
驅動讀
*/
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;
}


/*
驅動寫
*/
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;
}


/*
驅動控制
*/
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;
}

硬件注冊方式：以LED為例，初始化接口void led_register(void)，需要在初始化中調用。

#include?"stm32f0xx.h"
#include?"led.h"
#include?"cola_device.h"
#define?PORT_GREEN_LED?GPIOC??????????????????
#define PIN_GREENLED GPIO_Pin_13             


/*?LED亮、滅、變化?*/
#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);
}

應用層app代碼:

#include?
#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狀態改變一次
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);
}

這樣 app.c 文件中就不需要調用 led.h 頭文件了，rtt 就是這樣實現的。

四、總結

這樣就可以實現軟硬件分層了，是不是非常好用！

五、代碼下載鏈接

https://gitee.com/schuck/cola_os

編輯：黃飛

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