#include #include #include #include #include #include #include #include #include static unsigned short ignore[] = { I2C_CLIENT_END }; static unsigned short normal_addr[] = { 0x50, I2C_CLIENT_END }; /* 地址值是7位 */ /* 改为0x60的话, 由于不存在设备地址为0x60的设备, 所以at24cxx_detect不被调用 */ static unsigned short force_addr[] = {ANY_I2C_BUS, 0x60, I2C_CLIENT_END}; static unsigned short * forces[] = {force_addr, NULL}; static struct i2c_client_address_data addr_data = { .normal_i2c = normal_addr, /* 要发出S信号和设备地址并得到ACK信号,才能确定存在这个设备 */ .probe = ignore, .ignore = ignore, //.forces = forces, /* 强制认为存在这个设备 */ }; static struct i2c_driver at24cxx_driver; static int major; static struct class *cls; struct i2c_client *at24cxx_client; static ssize_t at24cxx_read(struct file *file, char __user *buf, size_t size, loff_t * offset) { unsigned char address; unsigned char data; struct i2c_msg msg[2]; int ret; /* address = buf[0] * data = buf[1] */ if (size != 1) return -EINVAL; copy_from_user(&address, buf, 1); /* 数据传输三要素: 源,目的,长度 */ /* 读AT24CXX时,要先把要读的存储空间的地址发给它 */ msg[0].addr = at24cxx_client->addr; /* 目的 */ msg[0].buf = &address; /* 源 */ msg[0].len = 1; /* 地址=1 byte */ msg[0].flags = 0; /* 表示写 */ /* 然后启动读操作 */ msg[1].addr = at24cxx_client->addr; /* 源 */ msg[1].buf = &data; /* 目的 */ msg[1].len = 1; /* 数据=1 byte */ msg[1].flags = I2C_M_RD; /* 表示读 */ ret = i2c_transfer(at24cxx_client->adapter, msg, 2); if (ret == 2) { copy_to_user(buf, &data, 1); return 1; } else return -EIO; } static ssize_t at24cxx_write(struct file *file, const char __user *buf, size_t size, loff_t *offset) { unsigned char val[2]; struct i2c_msg msg[1]; int ret; /* address = buf[0] * data = buf[1] */ if (size != 2) return -EINVAL; copy_from_user(val, buf, 2); /* 数据传输三要素: 源,目的,长度 */ msg[0].addr = at24cxx_client->addr; /* 目的 */ msg[0].buf = val; /* 源 */ msg[0].len = 2; /* 地址+数据=2 byte */ msg[0].flags = 0; /* 表示写 */ ret = i2c_transfer(at24cxx_client->adapter, msg, 1); if (ret == 1) return 2; else return -EIO; } static struct file_operations at24cxx_fops = { .owner = THIS_MODULE, .read = at24cxx_read, .write = at24cxx_write, }; static int at24cxx_detect(struct i2c_adapter *adapter, int address, int kind) { printk("at24cxx_detect "); /* 构构一个i2c_client结构体: 以后收改数据时会用到它 */ at24cxx_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL); at24cxx_client->addr = address; at24cxx_client->adapter = adapter; at24cxx_client->driver = &at24cxx_driver; strcpy(at24cxx_client->name, "at24cxx"); i2c_attach_client(at24cxx_client); major = register_chrdev(0, "at24cxx", &at24cxx_fops); cls = class_create(THIS_MODULE, "at24cxx"); class_device_create(cls, NULL, MKDEV(major, 0), NULL, "at24cxx"); /* /dev/at24cxx */ return 0; } static int at24cxx_attach(struct i2c_adapter *adapter) { return i2c_probe(adapter, &addr_data, at24cxx_detect); } static int at24cxx_detach(struct i2c_client *client) { printk("at24cxx_detach "); class_device_destroy(cls, MKDEV(major, 0)); class_destroy(cls); unregister_chrdev(major, "at24cxx"); i2c_detach_client(client); kfree(i2c_get_clientdata(client)); return 0; } /* 1. 分配一个i2c_driver结构体 */ /* 2. 设置i2c_driver结构体 */ static struct i2c_driver at24cxx_driver = { .driver = { .name = "at24cxx", }, .attach_adapter = at24cxx_attach, .detach_client = at24cxx_detach, }; static int at24cxx_init(void) { i2c_add_driver(&at24cxx_driver); return 0; } static void at24cxx_exit(void) { i2c_del_driver(&at24cxx_driver); } module_init(at24cxx_init); module_exit(at24cxx_exit); MODULE_LICENSE("GPL");
#include #include #include #include #include #include /* i2c_test r addr * i2c_test w addr val */ void print_usage(char *file) { printf("%s r addr ", file); printf("%s w addr val ", file); } int main(int argc, char **argv) { int fd; unsigned char buf[2]; if ((argc != 3) && (argc != 4)) { print_usage(argv[0]); return -1; } fd = open("/dev/at24cxx", O_RDWR); if (fd < 0) { printf("can't open /dev/at24cxx "); return -1; } if (strcmp(argv[1], "r") == 0) { buf[0] = strtoul(argv[2], NULL, 0); read(fd, buf, 1); printf("data: %c, %d, 0x%2x ", buf[0], buf[0], buf[0]); } else if (strcmp(argv[1], "w") == 0) { buf[0] = strtoul(argv[2], NULL, 0); buf[1] = strtoul(argv[3], NULL, 0); write(fd, buf, 2); } else { print_usage(argv[0]); return -1; } return 0; } 代码出自“韦东山视频”。
I2C设备驱动流程：1、构造i2c_driverstatic struct i2c_driver at24cxx_driver = {
    .driver = {
        .name    = "at24cxx",
    },
    .attach_adapter = at24cxx_attach,
    .detach_client  = at24cxx_detach,
};2、注册i2c_add_driver(&at24cxx_driver)
3、使用i2c_driver->attach_adapter发出设备地址信号，看设备是否响应ACK4、若响应，调用at24cxx_detect，构造i2c_client，注册字符设备at24cxx5、读写i2c设备    a、构造i2c_msg    b、使用i2c_transfer发出i2c_msg6、detach_client做清理工作