Linux 内核I2C设备驱动代码模板

Linux内核版本：Linux 4.4.153

设备树：

hello@3e {
	       compatible = "HELLO1,HELLO2";
	       reg = <0x3e>;
       };

驱动代码：

#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/slab.h>

struct hello_data {
	struct i2c_client	*client;
};

/* 从i2c读数据 */
static int hello_i2c_reg_read(struct i2c_client *client, unsigned char addr)
{
	return i2c_smbus_read_byte_data(client, addr & 0xff);
}


/* 向i2c写数据 */
static int hello_i2c_reg_write(struct i2c_client *client,
			unsigned char addr, unsigned char val)
{
	return i2c_smbus_write_byte_data(client, addr & 0xff, val);
}

static int hello_probe(struct i2c_client *client,
			       const struct i2c_device_id *dev_id)
{
    struct hello_data* hello;

    hello = kzalloc(sizeof(struct hello_data), GFP_KERNEL);
	if (!hello) {
		err("alloc hello err!");
		return -ENOMEM;
	}

	hello->client = client;
	printk(KERN_DEBUG "enter! addr=0x%x, name=%s\n", 
		client->addr, client->name);

	return 0;
}

static int hello_remove(struct i2c_client *client)
{
	return 0;
}

static int __maybe_unused hello_suspend(struct device *dev)
{
	return 0;
}

static int __maybe_unused hello_resume(struct device *dev)
{
	return 0;
}

static SIMPLE_DEV_PM_OPS(hello_pm, hello_suspend,
			 hello_resume);


static const struct of_device_id hello_of_match[] = {
	{.compatible = "HELLO1,HELLO2",},
	{}
};

static const struct i2c_device_id hello_id_table[] = {
	{ "hello_i2c", 0 },
	{}
};
MODULE_DEVICE_TABLE(i2c, hello_id_table);

static struct i2c_driver hello_driver = {
	.driver = {
		.name = "hello",
		.owner = THIS_MODULE,
		.of_match_table = of_match_ptr(hello_of_match),
		.pm = &hello_pm,
	},

	.probe		= hello_probe,
	.remove		= hello_remove,

	.id_table	= hello_id_table,
};

module_i2c_driver(hello_driver);

MODULE_DESCRIPTION("xxxxxx hello driver");
MODULE_AUTHOR("Liuguichao");
MODULE_LICENSE("GPL");

笔记：

1. 设备树中的compatible属性在I2C中的使用
假如设备树中 compatible = "x1x1,x2x2x2x2,x3x3";
在struct i2c_client *client中，
client->name = "x2x2x2x2,x3x3";
client->name限定在20个字符以内，不管compatible有多长，都会显示第一个逗号后面19个字符加一个'\0'字符。

2. struct i2c_client *client->adapter->nr

这个值标记了当前所用的I2C是第几组I2C,对应设备树种的i2c_1,i2c_2等等后面这个数字。