代码示例_i2c读写e2prom驱动

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#include <linux/init.h>
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/miscdevice.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/device.h>


//声明一个i2c client指针--保存probe中的i2c client
static struct i2c_client *at24_client;
static struct miscdevice  e2prom_misc;


//重写类似于i2c_master_send()/i2c_master_recv()
int at24_i2c_send(struct i2c_client *client, char *buf, int count)
{
    int ret;
    
    struct i2c_adapter *adapter = client->adapter;
    struct i2c_msg msg;
    
    msg.addr = client->addr;
    msg.flags = 0; //读1还是写0
    msg.len = count; 
    msg.buf = buf;
    //参数1---适配器--来自于i2c client 
    //参数2--数据包
    //参数3--数据包的个数
    //返回值--正确返回消息的个数，错误返回负数
    ret = i2c_transfer(adapter, &msg, 1);

    return ret==1?count:ret;
    
}

int at24_i2c_recv(struct i2c_client *client, char *buf, int count)
{
    int ret;
    
    struct i2c_adapter *adapter = client->adapter;
    struct i2c_msg msg;
    
    msg.addr = client->addr;
    msg.flags = 1; //读1还是写0
    msg.len = count; 
    msg.buf = buf;
    //参数1---适配器--来自于i2c client 
    //参数2--数据包
    //参数3--数据包的个数
    //返回值--正确返回消息的个数，错误返回负数
    ret = i2c_transfer(adapter, &msg, 1);

    return ret==1?count:ret;

}


const struct file_operations at24_fops = {


};


int at24_drv_probe(struct i2c_client *client, const struct i2c_device_id *id)
{

    printk("id->name = %s, id->driver_data = 0x%x
", id->name, id->driver_data);

    // 0- 保存i2c_client 
    at24_client = client;

    // 1， 与用户交互
    e2prom_misc.name = "at24_dev";
    e2prom_misc.minor = MISC_DYNAMIC_MINOR,
    e2prom_misc.fops = &at24_fops,
    misc_register(&e2prom_misc);

    // 2, 与硬件交互(初始化硬件)--最终委托i2c adpater层与硬件打交道
    // e2prom上电就能工作，并不需要特定一些初始化
    //以下代码主要演示如何操作从设备


    int ret;
    
    char sendbuf[10] = {0x8/*写的地址*/, 0x1b, 0x2b, 0x3b, 0x4b, 0x5b, 0x6b, 0x7b, 0x8b, 0x9b};

    ret = at24_i2c_send(client, sendbuf, 10);
    if(ret < 0)
    {
        printk("at24_i2c_send error
");
        misc_deregister(&e2prom_misc);
        return ret;
    }

    mdelay(3);
    //验证是否写入正确
    //先写地址
    char addr  = 0x8;
    ret = at24_i2c_send(client, &addr, 1);
    if(ret < 0)
    {
        printk("at24_i2c_send error
");
        misc_deregister(&e2prom_misc);
        return ret;
    }
    char recvbuf[8];
    ret = at24_i2c_recv(client, recvbuf, 8);
    if(ret < 0)
    {
        printk("at24_i2c_recv error
");
        misc_deregister(&e2prom_misc);
        return ret;
    }
    int i;
    for(i=0; i<8; i++)
        printk("recvbuf[%d] = 0x%x
", i, recvbuf[i]);
    
    
    return 0;

    
}



int at24_drv_remove(struct i2c_client *client)
{
    misc_deregister(&e2prom_misc);
    
    return 0;
}



const struct i2c_device_id at24_id_table[] = {
        {"at24c02", 0x2},
        {"at24c04", 0x4},
        {"at24c08", 0x5},
        {"at24c16", 0x6},
        {},
};


struct i2c_driver at24_i2c_drv = {
    .probe = at24_drv_probe,
    .remove = at24_drv_remove,
    .driver = {
        .name = "at24_drv", //一定要有--/sys/bus/i2c/drivers/at24_drv
    },
    .id_table = at24_id_table,

};


static int __init at24_i2c_drv_init(void)
{

    //注册一个i2c driver 
    return i2c_add_driver(&at24_i2c_drv);
    

}

static void __exit at24_i2c_drv_exit(void)
{
    i2c_del_driver(&at24_i2c_drv);
}


late_initcall(at24_i2c_drv_init);
module_exit(at24_i2c_drv_exit);
MODULE_LICENSE("GPL");

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CROSS_COMPILE = arm-none-linux-gnueabi-
CC = $(CROSS_COMPILE)gcc

#指定内核源码路径
KERNEL_DIR = /home/kernel/linux-3.0.8
CUR_DIR = $(shell pwd)

#MYAPP = plat_led_app

MODULE = at24_i2c_drv

all:
    #让make进入内核源码编译，同时将当前目录中的c程序作为内核模块一起编译
    make -C $(KERNEL_DIR) M=$(CUR_DIR) modules
ifneq ($(MYAPP), )    
    $(CC)  -o $(MYAPP) $(MYAPP).c
endif

clean:
    #删除上面编译生成的文件
    make -C $(KERNEL_DIR) M=$(CUR_DIR) clean
    rm -rf $(MYAPP)

install:
    cp *.ko $(MYAPP) /opt/rootfs/drv_module

#指定当前目录下哪个文件作为内核模块编
obj-m += $(MODULE).o

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