一、前言
以STM32爲例,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於硬件層的,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,爲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
/*
驅動註冊
*/
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;
};
/*
驅動註冊
*/
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 <string.h>
#include <stdbool.h>
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;
}
/*
驅動註冊
*/
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;
}
硬件註冊方式:以LED爲例,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 <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