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  • I2C用户态驱动设计

    一、用户态驱动模型


    1.1 I2C通用驱动代码
    i2c_dev_init:
    1. static int __init i2c_dev_init(void)
    2. {
    3.     int res;

    5.     printk(KERN_INFO "i2c /dev entries driver ");

    7.     res = register_chrdev(I2C_MAJOR, "i2c", &i2cdev_fops);                                        //早期注册字符设备
    8.     if (res)
    9.         goto out;

    11.     i2c_dev_class = class_create(THIS_MODULE, "i2c-dev");                                         //生成自动创建字符设备文件
    12.     if (IS_ERR(i2c_dev_class)) {
    13.         res = PTR_ERR(i2c_dev_class);
    14.         goto out_unreg_chrdev;
    15.     }

    17.     res = i2c_add_driver(&i2cdev_driver);                                                          //注册一个I2C的设备驱动
    18.     if (res)
    19.         goto out_unreg_class;

    21.     return 0;

    23. out_unreg_class:
    24.     class_destroy(i2c_dev_class);
    25. out_unreg_chrdev:
    26.     unregister_chrdev(I2C_MAJOR, "i2c");
    27. out:
    28.     printk(KERN_ERR "%s: Driver Initialisation failed ", __FILE__);
    29.     return res;
    30. }
    i2cdev_fops:
    1. static const struct file_operations i2cdev_fops = {
    2.     .owner        = THIS_MODULE,
    3.     .llseek        = no_llseek,
    4.     .read        = i2cdev_read,
    5.     .write        = i2cdev_write,
    6.     .unlocked_ioctl    = i2cdev_ioctl,
    7.     .open        = i2cdev_open,
    8.     .release    = i2cdev_release,
    9. };
    i2cdev_ioctl:
    1. static long i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
    2. {
    3.     struct i2c_client *client = (struct i2c_client *)file->private_data;
    4.     unsigned long funcs;

    6.     dev_dbg(&client->adapter->dev, "ioctl, cmd=0x%02x, arg=0x%02lx ",
    7.         cmd, arg);

    9.     switch ( cmd ) {
    10.     case I2C_SLAVE:
    11.     case I2C_SLAVE_FORCE:
    12.         /* NOTE: devices set up to work with "new style" drivers
    13.          * can't use I2C_SLAVE, even when the device node is not
    14.          * bound to a driver. Only I2C_SLAVE_FORCE will work.
    15.          *
    16.          * Setting the PEC flag here won't affect kernel drivers,
    17.          * which will be using the i2c_client node registered with
    18.          * the driver model core. Likewise, when that client has
    19.          * the PEC flag already set, the i2c-dev driver won't see
    20.          * (or use) this setting.
    21.          */
    22.         if ((arg > 0x3ff) ||
    23.          (((client->flags & I2C_M_TEN) == 0) && arg > 0x7f))
    24.             return -EINVAL;
    25.         if (cmd == I2C_SLAVE && i2cdev_check_addr(client->adapter, arg))
    26.             return -EBUSY;
    27.         /* REVISIT: address could become busy later */
    28.         client->addr = arg;
    29.         return 0;
    30.     case I2C_TENBIT:
    31.         if (arg)
    32.             client->flags |= I2C_M_TEN;
    33.         else
    34.             client->flags &= ~I2C_M_TEN;
    35.         return 0;
    36.     case I2C_PEC:
    37.         if (arg)
    38.             client->flags |= I2C_CLIENT_PEC;
    39.         else
    40.             client->flags &= ~I2C_CLIENT_PEC;
    41.         return 0;
    42.     case I2C_FUNCS:
    43.         funcs = i2c_get_functionality(client->adapter);
    44.         return put_user(funcs, (unsigned long __user *)arg);

    46.     case I2C_RDWR:                                                                             //这里是读写命令
    47.         return i2cdev_ioctl_rdrw(client, arg);

    49.     case I2C_SMBUS:
    50.         return i2cdev_ioctl_smbus(client, arg);

    52.     case I2C_RETRIES:
    53.         client->adapter->retries = arg;
    54.         break;
    55.     case I2C_TIMEOUT:
    56.         /* For historical reasons, user-space sets the timeout
    57.          * value in units of 10 ms.
    58.          */
    59.         client->adapter->timeout = msecs_to_jiffies(arg * 10);
    60.         break;
    61.     default:
    62.         /* NOTE: returning a fault code here could cause trouble
    63.          * in buggy userspace code. Some old kernel bugs returned
    64.          * zero in this case, and userspace code might accidentally
    65.          * have depended on that bug.
    66.          */
    67.         return -ENOTTY;
    68.     }
    69.     return 0;
    70. }
    i2cdev_ioctl_rdrw:
    1. static noinline int i2cdev_ioctl_rdrw(struct i2c_client *client,
    2.         unsigned long arg)
    3. {
    4.     struct i2c_rdwr_ioctl_data rdwr_arg;
    5.     struct i2c_msg *rdwr_pa;
    6.     u8 __user **data_ptrs;
    7.     int i, res;

    9.     if (copy_from_user(&rdwr_arg,
    10.              (struct i2c_rdwr_ioctl_data __user *)arg,                        //传给ioctl的arg值，强制转换成i2c_rdwr_ioctl_data
    11.              sizeof(rdwr_arg)))
    12.         return -EFAULT;

    14.     /* Put an arbitrary limit on the number of messages that can
    15.      * be sent at once */
    16.     if (rdwr_arg.nmsgs > I2C_RDRW_IOCTL_MAX_MSGS)
    17.         return -EINVAL;

    19.     rdwr_pa = (struct i2c_msg *)
    20.         kmalloc(rdwr_arg.nmsgs * sizeof(struct i2c_msg),
    21.         GFP_KERNEL);
    22.     if (!rdwr_pa)
    23.         return -ENOMEM;

    25.     if (copy_from_user(rdwr_pa, rdwr_arg.msgs,
    26.              rdwr_arg.nmsgs * sizeof(struct i2c_msg))) {
    27.         kfree(rdwr_pa);
    28.         return -EFAULT;
    29.     }

    31.     data_ptrs = kmalloc(rdwr_arg.nmsgs * sizeof(u8 __user *), GFP_KERNEL);
    32.     if (data_ptrs == NULL) {
    33.         kfree(rdwr_pa);
    34.         return -ENOMEM;
    35.     }

    37.     res = 0;
    38.     for (i = 0; i < rdwr_arg.nmsgs; i++) {
    39.         /* Limit the size of the message to a sane amount;
    40.          * and don't let length change either. */
    41.         if ((rdwr_pa[i].len > 8192) ||
    42.          (rdwr_pa[i].flags & I2C_M_RECV_LEN)) {
    43.             res = -EINVAL;
    44.             break;
    45.         }
    46.         data_ptrs[i] = (u8 __user *)rdwr_pa[i].buf;
    47.         rdwr_pa[i].buf = kmalloc(rdwr_pa[i].len, GFP_KERNEL);
    48.         if (rdwr_pa[i].buf == NULL) {
    49.             res = -ENOMEM;
    50.             break;
    51.         }
    52.         if (copy_from_user(rdwr_pa[i].buf, data_ptrs[i],
    53.                  rdwr_pa[i].len)) {
    54.                 ++i; /* Needs to be kfreed too */
    55.                 res = -EFAULT;
    56.             break;
    57.         }
    58.     }
    59.     if (res < 0) {
    60.         int j;
    61.         for (j = 0; j < i; ++j)
    62.             kfree(rdwr_pa[j].buf);
    63.         kfree(data_ptrs);
    64.         kfree(rdwr_pa);
    65.         return res;
    66.     }

    68.     res = i2c_transfer(client->adapter, rdwr_pa, rdwr_arg.nmsgs);                           //发送数据来源于i2c核心
    69.     while (i-- > 0) {
    70.         if (res >= 0 && (rdwr_pa[i].flags & I2C_M_RD)) {
    71.             if (copy_to_user(data_ptrs[i], rdwr_pa[i].buf,
    72.                      rdwr_pa[i].len))
    73.                 res = -EFAULT;
    74.         }
    75.         kfree(rdwr_pa[i].buf);
    76.     }
    77.     kfree(data_ptrs);
    78.     kfree(rdwr_pa);
    79.     return res;
    80. }
    i2c_rdwr_ioctl_data:
    1. struct i2c_rdwr_ioctl_data {
    2.     struct i2c_msg __user *msgs;    /* pointers to i2c_msgs */                    消息指针
    3.     __u32 nmsgs;            /* number of i2c_msgs */                              有多少条消息
    4. };
    一条消息（一个读操作和写操作）：

    1. struct i2c_msg {
    2.     __u16 addr;    /* slave address            */                                //从设备地址
    3.     __u16 flags;                                                                 //读还是写
    4. #define I2C_M_TEN        0x0010    /* this is a ten bit chip address */
    5. #define I2C_M_RD        0x0001    /* read data, from slave to master */
    6. #define I2C_M_NOSTART        0x4000    /* if I2C_FUNC_PROTOCOL_MANGLING */
    7. #define I2C_M_REV_DIR_ADDR    0x2000    /* if I2C_FUNC_PROTOCOL_MANGLING */
    8. #define I2C_M_IGNORE_NAK    0x1000    /* if I2C_FUNC_PROTOCOL_MANGLING */
    9. #define I2C_M_NO_RD_ACK        0x0800    /* if I2C_FUNC_PROTOCOL_MANGLING */
    10. #define I2C_M_RECV_LEN        0x0400    /* length will be first received byte */
    11.     __u16 len;        /* msg length                */                             //消息里面有多少字节
    12.     __u8 *buf;        /* pointer to msg data            */                        //消息里面的数据
    13. };
    i2c_transfer:
    1. int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
    2. {
    3.     int ret;

    5.     if (adap->algo->master_xfer) {
    6. #ifdef DEBUG
    7.         for (ret = 0; ret < num; ret++) {
    8.             dev_dbg(&adap->dev, "master_xfer[%d] %c, addr=0x%02x, "
    9.                 "len=%d%s ", ret, (msgs[ret].flags & I2C_M_RD)
    10.                 ? 'R' : 'W', msgs[ret].addr, msgs[ret].len,
    11.                 (msgs[ret].flags & I2C_M_RECV_LEN) ? "+" : "");
    12.         }
    13. #endif

    15.         if (in_atomic() || irqs_disabled()) {
    16.             ret = mutex_trylock(&adap->bus_lock);
    17.             if (!ret)
    18.                 /* I2C activity is ongoing. */
    19.                 return -EAGAIN;
    20.         } else {
    21.             mutex_lock_nested(&adap->bus_lock, adap->level);
    22.         }

    24.         ret = adap->algo->master_xfer(adap,msgs,num);                               //找到adapter（控制器）->algo(算法）->master_xfer（发送）
    25.         mutex_unlock(&adap->bus_lock);

    27.         return ret;
    28.     } else {
    29.         dev_dbg(&adap->dev, "I2C level transfers not supported ");
    30.         return -EOPNOTSUPP;
    31.     }
    32. }

    二、EEPROM用户态驱动编写
    i2c-app-drv.c:
    1. #include <sys/stat.h>
    2. #include <fcntl.h>
    3. #include <stdio.h>
    4. #include <unistd.h>
    5. #include <linux/types.h>

    7. #define I2C_RDWR 0x0707

    9. struct i2c_msg {
    10.     unsigned short addr;    /* slave address            */
    11.     unsigned short flags;
    12.     unsigned short len;        /* msg length                */
    13.     unsigned char *buf;        /* pointer to msg data            */
    14. };

    16. struct i2c_rdwr_ioctl_data {
    17.     struct i2c_msg *msgs;    /* pointers to i2c_msgs */
    18.     unsigned int nmsgs;            /* number of i2c_msgs */
    19. };

    21. int main()
    22. {
    23.     int fd;
    24.     struct i2c_rdwr_ioctl_data e2prom_data;

    26.     //1.打开通用设备文件
    27.     fd = open("/dev/i2c-0", O_RDWR);
    28.     
    29.     e2prom_data.msgs = (struct i2c_msg *)malloc(2*sizeof(struct i2c_msg));
    30.     
    31.     //2.构造写数据到eeprom的消息
    32.     e2prom_data.nmsgs = 1;
    33.     (e2prom_data.msgs[0]).len = 2;
    34.     (e2prom_data.msgs[0]).addr = 0x50;
    35.     (e2prom_data.msgs[0]).flags = 0;
    36.     (e2prom_data.msgs[0]).buf = (unsigned char *)malloc(2);
    37.     (e2prom_data.msgs[0]).buf[0] = 0x10;
    38.     (e2prom_data.msgs[0]).buf[1] = 0xF0;

    40.     //3.利用ioctl写入数据
    41.     ioctl(fd, I2C_RDWR, (unsigned long)&e2prom_data);

    43.     //4.构造从eeprom读书据的消息
    44.     e2prom_data.nmsgs = 2;
    45.     (e2prom_data.msgs[0]).len = 1;
    46.     (e2prom_data.msgs[0]).addr = 0x50;
    47.     (e2prom_data.msgs[0]).flags = 0;
    48.     (e2prom_data.msgs[0]).buf[0] = 0x10;

    50.     (e2prom_data.msgs[1]).len = 1;
    51.     (e2prom_data.msgs[1]).addr = 0x50;
    52.     (e2prom_data.msgs[1]).flags = 1;
    53.     (e2prom_data.msgs[1]).buf = (unsigned char *)malloc(2);
    54.     (e2prom_data.msgs[1]).buf[0] = 0;

    56.     //5.使用ioctl读出数据
    57.     ioctl(fd, I2C_RDWR, (unsigned long)&e2prom_data);
    58.     printf("buf[0]=%x ",(e2prom_data.msgs[1]).buf[0]);
    59.     //6.关闭设备
    60.     close(fd);
    61. }
    遇到的问题：
    1. # ./i2c-app-drv
    2. s3c2440-i2c s3c2440-i2c: cannot get bus (error -110)
    3. s3c2440-i2c s3c2440-i2c: cannot get bus (error -110)
    4. s3c2440-i2c s3c2440-i2c: cannot get bus (error -110)
    5. s3c2440-i2c s3c2440-i2c: cannot get bus (error -110)
    6. buf[0]=0
    内核中的i2c和视频模块冲突了。所以要在内核中去掉视频模块：
    Device Drivers>>Multimedia devices>>Video For Linux

    结果：
    1. # ./i2c-app-drv
    2. buf[0]=f0










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  • 原文地址：https://www.cnblogs.com/ch122633/p/7363294.html
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