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Linux I2C驅(qū)動(dòng)注冊(cè)詳解

更新時(shí)間：2025年07月22日 09:24:45 作者：大肥周

文章介紹了I2C驅(qū)動(dòng)注冊(cè)機(jī)制,核心是structi2c_driver結(jié)構(gòu)體,需填充name、probe和id_table字段,name用于顯示驅(qū)動(dòng)名稱,probe在設(shè)備匹配后調(diào)用（無(wú)論設(shè)備是否存在）,通過(guò)設(shè)備樹(shù)或靜態(tài)注冊(cè)識(shí)別設(shè)備,最終觸發(fā)驅(qū)動(dòng)探針流程

注冊(cè)接口

#define i2c_add_driver(driver) \
       i2c_register_driver(THIS_MODULE, driver)

int i2c_register_driver(struct module *owner, struct i2c_driver *driver)

注冊(cè)的結(jié)構(gòu)體是struct i2c_driver，主要填充name、probe和id_table字段，其中name是驅(qū)動(dòng)名稱，到時(shí)會(huì)在/sys/bus/i2c/drivers顯示這個(gè)驅(qū)動(dòng)名稱，probe會(huì)在I2C設(shè)備匹配后調(diào)用，不是發(fā)現(xiàn)I2C設(shè)備，即便實(shí)際上這個(gè)設(shè)備不在，但是代碼里注冊(cè)了這個(gè)設(shè)備，或者設(shè)備樹(shù)里配置了這個(gè)設(shè)備，就會(huì)被調(diào)用。

driver.of_match_table和 id_table兩個(gè)成員列出的是驅(qū)動(dòng)程序所能支持的所有設(shè)備，其中driver.of_match_table里的設(shè)備，是跟設(shè)備樹(shù)匹配的，id_table是跟靜態(tài)注冊(cè)是調(diào)用的struct i2c_board_info里的name做比較的。

示例代碼

驅(qū)動(dòng)注冊(cè)：

static int __devinit zsl_i2c_drv_probe(struct i2c_client *client, const struct i2c_device_id *id)
{	
	struct property *pp = NULL;
	uint8_t buf[4];
	struct i2c_msg msgs[2] = {{0}, {0}};
	int len = sizeof(msgs) / sizeof(msgs[0]);

	printk(KERN_INFO "%s: %x\n",__func__,client->addr);

	pp = of_find_property(client->dev.of_node, "testdata", NULL);
	if (pp)
		printk(KERN_INFO "%s: %d:%s \n",__func__,pp->length,(char *)pp->value);
	
	dump_stack();

	if (client->adapter)
	{
		buf[0] = 0;
		buf[1] = 4;
		buf[2] = 0;
		buf[3] = 0;
		memset(msgs,0,sizeof(struct i2c_msg)*2);
		msgs[0].addr  = client->addr;
		msgs[0].flags = 0x0;
		msgs[0].len   = 2;
		msgs[0].buf   = buf;
		
		msgs[1].addr  = client->addr;
		msgs[1].flags = I2C_M_RD;
		msgs[1].len   = 4;
		msgs[1].buf   = buf;

		if (i2c_transfer(client->adapter, msgs,	len) == len)
			printk(KERN_INFO "zsl i2c_transfer r: %d:%x %x %x %x\n",len,buf[0],buf[1],buf[2],buf[3]);
		
		buf[0] = 0;
		buf[1] = 4;
		buf[2] = 7;
		buf[3] = 8;

		memset(msgs,0,sizeof(struct i2c_msg)*2);
		msgs[0].addr = client->addr;
		msgs[0].flags = 0;
		msgs[0].len = 4;
		msgs[0].buf = buf;
		
		if (i2c_transfer(client->adapter, msgs,	1) == 1)
			printk(KERN_INFO "zsl i2c_transfer w: %d:%x %x %x %x\n",1,buf[0],buf[1],buf[2],buf[3]);

		buf[0] = 0;
		buf[1] = 4;
		buf[2] = 0;
		buf[3] = 0;
		memset(msgs,0,sizeof(struct i2c_msg)*2);
		msgs[0].addr  = client->addr;
		msgs[0].flags = 0x0;
		msgs[0].len   = 2;
		msgs[0].buf   = buf;
		
		msgs[1].addr  = client->addr;
		msgs[1].flags = I2C_M_RD;
		msgs[1].len   = 4;
		msgs[1].buf   = buf;
		msleep(100);
		len = i2c_transfer(client->adapter, msgs, len);
		if (2 == len)
			printk(KERN_INFO "zsl i2c_transfer r: %d:%x %x %x %x\n",len,buf[0],buf[1],buf[2],buf[3]);				
	}
	
    return 0;
}
 
static void __devexit zsl_i2c_drv_remove(struct i2c_client *client)
{
	printk(KERN_INFO "%s: \n",__func__);
}
 
static const struct i2c_device_id zsl_dev_id_table[] = {
    { "zsl_i2c_dev", 0 },
    {}
};//這里的名字很重要，驅(qū)動(dòng)第一種匹配設(shè)備的方式要用到
 
static const struct of_device_id zsl_of_match_ids[] = {
	{ .compatible = "i2c_name,zsl",		.data = NULL },
	{ /* END OF LIST */ } //最后一項(xiàng)為空，用于判斷數(shù)組遍歷完成
};

static struct i2c_driver zsl_i2c_driver = {
    .driver        = {
        .name        = "zsl_i2c",
        .owner        = THIS_MODULE,
        .of_match_table = zsl_of_match_ids,//設(shè)備樹(shù)匹配用
    },
    .probe		= zsl_i2c_drv_probe,
    .remove		= __devexit_p(zsl_i2c_drv_remove),
    .id_table	= zsl_dev_id_table,  //設(shè)備樹(shù)不需要，i2c_register_board_info匹配使用
};

void zsl_i2c_drv_init(void)
{
    i2c_add_driver(&zsl_i2c_driver);
}

靜態(tài)設(shè)備注冊(cè)

static struct i2c_board_info zsl_i2c_dev = {
    I2C_BOARD_INFO("zsl_i2c_dev", 0x50),//這個(gè)名字很重要，用于匹配 I2C 驅(qū)動(dòng)
};

static struct i2c_client *zsl_i2c_client;

void zsl_i2c_dev_init(void)
{
       i2c_register_board_info(4, &zsl_i2c_dev, 1);
}

設(shè)備樹(shù)注冊(cè)

&i2c4 {
       zsli2c0: zsli2c@50 {
              compatible = "i2c_name,zsl";
              status = "okay";
              testdata = "asdfg";
              reg = <0x50>;
       };
};

運(yùn)行后probe就會(huì)被調(diào)用，無(wú)論配的是什么地址，0x50設(shè)備存在，0x60設(shè)備不存在，probe都能被調(diào)用，但是0x60的讀不到數(shù)據(jù)。

調(diào)用關(guān)系

probe里的堆棧打印如下：

從芯片廠家的I2C驅(qū)動(dòng)初始化接口rk3x_i2c_driver_init開(kāi)始，使用platform_driver_register接口注冊(cè)rk3x_i2c_driver，當(dāng)設(shè)備樹(shù)里有對(duì)應(yīng)的I2C總線時(shí)，就會(huì)注冊(cè)I2C設(shè)備，匹配后調(diào)用這里的probe接口rk3x_i2c_probe。

rk3x_i2c_probe里會(huì)初始化 Rockchip I2C控制器，調(diào)用 i2c_register_adapter將 I2C 適配器注冊(cè)到內(nèi)核，進(jìn)而調(diào)用of_i2c_register_devices 掃描設(shè)備樹(shù)，調(diào)用i2c_new_client_device創(chuàng)建配置的I2C設(shè)備。

i2c_new_client_device里會(huì)創(chuàng)建struct i2c_client并調(diào)用device_register注冊(cè)到內(nèi)核，觸發(fā) device_add，內(nèi)核會(huì)嘗試匹配驅(qū)動(dòng)（通過(guò) compatible 字符串或者name）。如果匹配成功，調(diào)用 i2c_device_probe到probe接口的zsl_i2c_drv_probe。