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
#include
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
#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
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