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楼主  发表于: 2013-04-07 14:01
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 加载I2C总线驱动为什么看不到主设备号

/********************************************
编译环境：linux 2.6.29内核
********************************************/

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <asm/uaccess.h>
#include <linux/i2c.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/delay.h>
#include <linux/kdev_t.h>



#define AT24C08B_MAJOR 250

static int at24c08b_major = AT24C08B_MAJOR;



struct at24c08b_dev
{
    struct i2c_client *client;
    char name[30];
    unsigned short current_pointer;
    struct cdev cdev;
};

struct at24c08b_dev *at24c08b_devp;


static int at24c08b_open (struct inode *inode, struct file *file)
{
    /*将设备描述结构指针赋值给文件私有数据指针*/
    file->private_data = at24c08b_devp;
    return 0;
}


static ssize_t at24c08b_read (struct file *file, char *buf, size_t count, loff_t * ppos)
{
    int i = 0;
    int transferred = 0;
    int ret, my_buf[512];
    struct at24c08b_dev *dev = (struct at24c08b_dev *) file->private_data;
    dev->current_pointer = *ppos;
    
    /* Return 1 if adapter supports everything we need, 0 if not. */
    if (i2c_check_functionality (dev->client->adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA))
    {
        while (transferred < count)
        {
            //SMBus "read byte" protocol
            ret =i2c_smbus_read_byte_data (dev->client,
                          dev->current_pointer + i);
            my_buf[i++] = (unsigned short) ret;
            transferred += 1;
        }
        
        /*读数据到用户空间*/
        copy_to_user (buf, (void *) my_buf, transferred);
        dev->current_pointer += transferred;
    }
    return transferred;
}


static ssize_t at24c08b_write (struct file *file, char *buf, size_t count, loff_t * ppos)
{
    int i = 0;
    int transferred = 0;
    int ret, my_buf[512];
    struct at24c08b_dev *dev = (struct at24c08b_dev *) file->private_data;
    dev->current_pointer = *ppos;
    
    if (i2c_check_functionality(dev->client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
    {
        
         /*从用户空间写入数据*/
        copy_from_user (my_buf, buf, count);
        
        while (transferred < count)
        {
            //SMBus "write byte" protocol
            ret =i2c_smbus_write_byte_data (dev->client,
                       dev->current_pointer + i,
                       my_buf);
            i += 1;
            transferred += 1;
        }
        dev->current_pointer += transferred;
    }
    return transferred;
}


static int at24c08b_ioctl (struct inode *inodep, struct file *file, unsigned int cmd,    unsigned long arg)
{
    return 0;
}


static int at24c08b_release (struct inode *inodep, struct file *file)
{
    file->private_data = NULL;
    return 0;
}


static const struct file_operations at24c08b_fops = {
    .owner = THIS_MODULE,
    .open = at24c08b_open,
    .read = at24c08b_read,
    .write = at24c08b_write,
    .ioctl = at24c08b_ioctl,
    .release = at24c08b_release,
};



//初始化字符设备，注册字符设备到系统
static void at24c08b_setup_cdev (struct at24c08b_dev *dev, int index)
{
    int err, devnum = MKDEV (at24c08b_major, index);
    cdev_init (&dev->cdev, &at24c08b_fops);
    dev->cdev.owner = THIS_MODULE;
    err = cdev_add (&dev->cdev, devnum, 1);
    if (err)
    printk (KERN_NOTICE "Error %d adding at24c08b %d", err, index);
}


#if 1
static int __devinit at24c08b_probe (struct i2c_client *client, const struct i2c_device_id *id)
{
    int ret;
    dev_t devnum;
    printk (KERN_NOTICE "at24c08b probe is start\n");    //调试用,看是否执行了probe 函数
    
    //dev_t devnum = MKDEV(at24c08b_major, 0);
    devnum = MKDEV(at24c08b_major, 0);
    
    
    if (at24c08b_major)        //静态申请设备号
        ret = register_chrdev_region(devnum, 1, "at24c08b");
    else
    {                         //动态分配设备号
        ret = alloc_chrdev_region(&devnum, 0, 1, "at24c08b");
        at24c08b_major = MAJOR (devnum);
    }
    
    if (ret < 0)
        return ret;
    
    at24c08b_devp = kmalloc(sizeof (struct at24c08b_dev), GFP_KERNEL);
    if (!at24c08b_devp)
    {
        ret = -ENOMEM;
        goto fail_malloc;
    }
    
    memset (at24c08b_devp, 0, sizeof (struct at24c08b_dev));
    at24c08b_devp->client = client;
    
    at24c08b_setup_cdev (at24c08b_devp, 0);            //注册字符设备到系统            
    return 0;
      
      fail_malloc:
        unregister_chrdev_region (devnum, 1);        //注销设备号
    
    return ret;

}
#endif





static int __devexit at24c08b_remove (struct i2c_client *client)
{
    cdev_del (&at24c08b_devp->cdev);
    kfree (at24c08b_devp);
    unregister_chrdev_region (MKDEV(at24c08b_major, 0), 1);
    return 0;
}




static const struct i2c_device_id at24c08b_id[] = {
    {"at24c08b", 0}, //这个0是不是有点奇怪啊, 呵呵
    {}
};


MODULE_DEVICE_TABLE (i2c, at24c08b_id);



static struct i2c_driver at24c08b_driver = {
    .driver = {
                   .name = "at24c08b",
                   .owner = THIS_MODULE,
                 },
    .probe = at24c08b_probe,
    .remove = __devexit_p (at24c08b_remove),
    .id_table = at24c08b_id,

};


static int __init at24c08b_init (void)
{

    int result;
    
    printk (KERN_NOTICE "at24c08b is insmod\n");
    //return i2c_add_driver (&at24c08b_driver);
    
    result = i2c_add_driver (&at24c08b_driver);
    
    printk (KERN_NOTICE "at24c08b is %d\n",result);    
    
    return    result;
        

}



void at24c08b_exit (void)
{
    printk (KERN_NOTICE "at24c08b is rmmod\n");
    i2c_del_driver (&at24c08b_driver);
}





MODULE_DESCRIPTION ("at24c08b eeprom driver");
MODULE_LICENSE ("Dual BSD/GPL");
MODULE_AUTHOR ("Weimeng Li <pursuitxh@163.com>");
MODULE_VERSION ("V1.0");


module_param (at24c08b_major, int, S_IRUGO);
module_init (at24c08b_init);
module_exit (at24c08b_exit);









//-----------------------------------------------------------------------
串口打印信息如下：
# lsmod
# insmod at24c08-driver.ko
at24c08b is insmod
at24c08b is 0
# lsmod
at24c08_driver 3752 0 - Live 0xbf000000
# cat /proc/devices
Character devices:
  1 mem
  4 /dev/vc/0
  4 tty
  5 /dev/tty
  5 /dev/console
  5 /dev/ptmx
  7 vcs
10 misc
13 input
14 sound
29 fb
81 video4linux
90 mtd
116 alsa
128 ptm
136 pts
180 usb
188 ttyUSB
189 usb_device
204 s3c2410_serial
253 usb_endpoint
254 rtc

Block devices:
259 blkext
  7 loop
  8 sd
31 mtdblock
65 sd
66 sd
67 sd
68 sd
69 sd
70 sd
71 sd
128 sd
129 sd
130 sd
131 sd
132 sd
133 sd
134 sd
135 sd
179 mmc
#


//----------------------------------------------------------------------------------------
加载内核后i2c_add_driver函数成功返回为0，但是在打印cat /proc/devices
没有找到i2c驱动的主设备编号250
分析串口打印信息中得知，说明没有调用probe函数，但设备名(at24c08b)与驱动名(at24c08b)只要匹配成功，
就应当调用probe函数，为什么这里没有调用probe函数？谢谢。
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1楼  发表于: 2013-04-07 20:51
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 回 楼主(sanmaoljh) 的帖子

分析串口打印信息中得知，说明没有调用probe函数，但设备名(at24c08b)与驱动名(at24c08b)只要匹配成功，

匹配的前提是有一个名字为"at24c08b"的i2c device注册到i2c bus上。也就是说，你在/sys/bus/i2c/devices下应该能看到一个X-00YY的链接指向这个设备的属性文件。其中，X是I2C Controller的编号，YY是at24c08b的7bit I2C地址。
"If you have an apple and I have an apple and we exchange apples, then you and I will
still each have one apple. But if you have an idea and I have an idea and we exchange
these ideas, then each of us will have two ideas."
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