i2c驱动问题

请教一下，我正在学习i2c驱动，想尝试从添加i2c_adapter开始，写了个简单的i2c驱动模块，但是执行到第79行ret = i2c_add_adapter(&i2c->adap);就崩溃了，各位大神麻烦帮小弟看一下是怎么回事。


#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <linux/cpufreq.h>
#include <linux/slab.h>
#include <linux/io.h>

static struct kaka_i2c_struct *i2c  = NULL;

struct kaka_i2c_struct {
    struct i2c_adapter    adap;
    struct device *dev;
};

static int ka_i2c_xfer(struct i2c_adapter *adap,
            struct i2c_msg *msgs, int num)
{
    struct kaka_i2c_struct *i2c = (struct kaka_i2c_struct *)adap->algo_data;
    printk("i2c is %p\n",i2c);
    printk("going to ka_i2c_xfer()\n");
    return 0;
}

/* i2c bus registration info */

static const struct i2c_algorithm s3c24xx_i2c_algorithm = {
    .master_xfer        = ka_i2c_xfer,
    //.functionality        = ka_i2c_func,
};


static int ka_i2c_probe(struct platform_device *pdev)
{
    int ret;

    printk("going to ka_i2c_probe()\n");
/*    pdata = pdev->dev.platform_data;
    if (!pdata) {
        dev_err(&pdev->dev, "no platform data\n");
        return -EINVAL;
    }
*/
    i2c = kzalloc(sizeof(struct kaka_i2c_struct), GFP_KERNEL);
    if (!i2c) {
        printk("no memory for state\n");
        return -ENOMEM;
    }

    memset(i2c,0,sizeof(*i2c));
    strlcpy(i2c->adap.name, "kakakakka-i2c", sizeof(i2c->adap.name));
    i2c->adap.owner   = THIS_MODULE;
    i2c->adap.algo    = &s3c24xx_i2c_algorithm;
    i2c->adap.retries = 2;
    i2c->adap.class   = I2C_CLASS_HWMON | I2C_CLASS_SPD;

    /* find the clock and enable it */

    i2c->dev = &pdev->dev;

    /* setup info block for the i2c core */

    i2c->adap.algo_data = i2c;
    i2c->adap.dev.parent = &pdev->dev;

    //i2c->adap.nr = pdata->bus_num;
    i2c->adap.nr = 1;
    printk("1\n");
    printk("%p\n",&i2c->adap);
    ret = i2c_add_adapter(&i2c->adap);
    printk("1.5\n");
    if (ret < 0) {
        printk("failed to add bus to i2c core\n");
    }
    printk("2\n");
    platform_set_drvdata(pdev, i2c);

    return 0;
}

static int ka_i2c_remove(struct platform_device *pdev)
{
    struct kaka_i2c_struct *i2c = platform_get_drvdata(pdev);
    printk("going to ka_i2c_remove()\n");
    i2c_del_adapter(&i2c->adap);

    return 0;
}

/* device driver for platform bus bits */

static struct platform_device_id ka_driver_ids[] = {
    {
        .name        = "ka-i2c",
    }, { },
};
MODULE_DEVICE_TABLE(platform, ka_driver_ids);

static struct platform_driver ka_i2c_driver = {
    .probe        = ka_i2c_probe,
    .remove        = ka_i2c_remove,
    .id_table    = ka_driver_ids,
    .driver        = {
        .owner    = THIS_MODULE,
        .name    = "lizhe-i2c", //same with i2c_device
    },
};

static void ka_device_release(struct device *dev)  
{  
    printk("ka_device_release\n");  
    return ;  
}

static struct platform_device i2c_device =  
{  
    .name = "ka-i2c",  //same with ka_i2c_driver
    .id = -1,  
    //.dev.release = ka_device_release,
};  

static int __init i2c_init(void)
{
    int ret;
    printk("i2c_device_init\n");
    ret = platform_device_register(&i2c_device);
    if(ret)
    {
        printk("platform_device_register fail\n");
        return ret;
    }
    ret = platform_driver_register(&ka_i2c_driver);
    if(ret)
    {
        printk("platform_driver_register fail\n");
        platform_device_unregister(&i2c_device);
        return ret;
    }
    return ret;
}
module_init(i2c_init);

static void __exit i2c_exit(void)
{
    printk("i2c_exit\n");
    platform_device_unregister(&i2c_device);
    platform_driver_unregister(&ka_i2c_driver);
}
module_exit(i2c_exit);

MODULE_DESCRIPTION("S3C24XX I2C Bus driver");
MODULE_AUTHOR("kaka");
MODULE_LICENSE("Dual BSD/GPL");