Linux驱动之I2C设备驱动 _设备驱动

高斋晓开卷，独共圣人语。这篇文章主要讲述Linux驱动之I2C设备驱动相关的知识，希望能为你提供帮助。

内核：4.20
芯片：HYM8563 RTC
下面的代码分析主要都在注释中，会按照驱动中函数的执行顺序分析。
一、加载和卸载函数

static const struct i2c_device_id hym8563_id[] = {
{ "hym8563", 0 },
{},
};
MODULE_DEVICE_TABLE(i2c, hym8563_id);

static const struct of_device_id hym8563_dt_idtable[] = {
{ .compatible = "haoyu,hym8563" },
{},
};
MODULE_DEVICE_TABLE(of, hym8563_dt_idtable);

static struct i2c_driver hym8563_driver = {
.driver= {
.name= "rtc-hym8563",
.pm= & hym8563_pm_ops,
.of_match_table= hym8563_dt_idtable, //dt匹配表
},
.probe= hym8563_probe,
.id_table= hym8563_id,// id表
};
// 封住了module_init()和module_exit()
// 里面会调用i2c_register_driver(hym8563_driver)
// 和i2c_del_driver(hym8563_driver)
module_i2c_driver(hym8563_driver);

二、probe()函数

static int hym8563_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct hym8563 *hym8563;
int ret;
//申请内存空间
hym8563 = devm_kzalloc(& client-> dev, sizeof(*hym8563), GFP_KERNEL);
if (!hym8563)
return -ENOMEM;
//保存数据
hym8563-> client = client;
i2c_set_clientdata(client, hym8563);
//HYM8563初始化
ret = hym8563_init_device(client);

//申请中断
if (client-> irq > 0) {
ret = devm_request_threaded_irq(& client-> dev, client-> irq,
NULL, hym8563_irq,
IRQF_TRIGGER_LOW | IRQF_ONESHOT,
client-> name, hym8563);
}

//检查一下模块是否正常运行
ret = i2c_smbus_read_byte_data(client, HYM8563_SEC);
if (ret < 0)
return ret;
//VL位用来标识模块是否正常工作
hym8563-> valid = !(ret & HYM8563_SEC_VL);
dev_dbg(& client-> dev, "rtc information is %s\\n",
hym8563-> valid ? "valid" : "invalid");
//注册RTC设备
hym8563-> rtc = devm_rtc_device_register(& client-> dev, client-> name,
& hym8563_rtc_ops, THIS_MODULE);

/* the hym8563 alarm only supports a minute accuracy */
hym8563-> rtc-> uie_unsupported = 1;

#ifdef CONFIG_COMMON_CLK
//HYM8563可以作为时钟源
hym8563_clkout_register_clk(hym8563);
#endif

return 0;
}

上面删掉了一些判断和Log信息。
三、HYM8563初始化

//查看datasheet对8563进行初始化，对寄存器进行设置
static int hym8563_init_device(struct i2c_client *client)
{
int ret;

/* Clear stop flag if present */
//向寄存器中写入值
ret = i2c_smbus_write_byte_data(client, HYM8563_CTL1, 0);
if (ret < 0)
return ret;
//读取寄存器的值
ret = i2c_smbus_read_byte_data(client, HYM8563_CTL2);
if (ret < 0)
return ret;

/* Disable alarm and timer interrupts */
ret & = ~HYM8563_CTL2_AIE;
ret & = ~HYM8563_CTL2_TIE;

/* Clear any pending alarm and timer flags */
if (ret & HYM8563_CTL2_AF)
ret & = ~HYM8563_CTL2_AF;

if (ret & HYM8563_CTL2_TF)
ret & = ~HYM8563_CTL2_TF;

ret & = ~HYM8563_CTL2_TI_TP;
//将修改后的值写入寄存器
return i2c_smbus_write_byte_data(client, HYM8563_CTL2, ret);
}

四、HYM8563操作函数

static int hym8563_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
struct i2c_client *client = to_i2c_client(dev);
struct hym8563 *hym8563 = i2c_get_clientdata(client);
u8 buf[7];
int ret;

if (!hym8563-> valid) {
dev_warn(& client-> dev, "no valid clock/calendar values available\\n");
return -EPERM;
}
//读取寄存器值，连续读取7个寄存器
ret = i2c_smbus_read_i2c_block_data(client, HYM8563_SEC, 7, buf);
//bcd数转成2进制
tm-> tm_sec = bcd2bin(buf[0] & HYM8563_SEC_MASK);
tm-> tm_min = bcd2bin(buf[1] & HYM8563_MIN_MASK);
tm-> tm_hour = bcd2bin(buf[2] & HYM8563_HOUR_MASK);
tm-> tm_mday = bcd2bin(buf[3] & HYM8563_DAY_MASK);
tm-> tm_wday = bcd2bin(buf[4] & HYM8563_WEEKDAY_MASK); /* 0 = Sun */
tm-> tm_mon = bcd2bin(buf[5] & HYM8563_MONTH_MASK) - 1; /* 0 = Jan */
tm-> tm_year = bcd2bin(buf[6]) + 100;

return 0;
}

static const struct rtc_class_ops hym8563_rtc_ops = {
.read_time= hym8563_rtc_read_time,
.set_time= hym8563_rtc_set_time,
.alarm_irq_enable= hym8563_rtc_alarm_irq_enable,
.read_alarm= hym8563_rtc_read_alarm,
.set_alarm= hym8563_rtc_set_alarm,
};