1、linux i2c 驱动一
2、linux i2c 驱动二
目录
系列文章目录
文章目录
前言
一、i2c协议简述
二、linux 下 i2c驱动框架
1.首先掌握如何使用
2.理解原理
三、实例
1、设备树
2、驱动代码
总结
最近在看VFS和汇编相关的东西,整的有点头大,好多东西没来得急整理。
本次主要想总结下串行总线iic,其实iic和spi都是低速串行总线,一般传感器(温度,光模块,eeprom等)都会挂载在iic总线下,是经常使用操作有比较简单的总线。
SPI一般都会挂载一下ad 类(如RF设备 adc9009) 时钟芯片(如 ad9543) GPS LCD 等都会用到SPI
本来准备一次性写完发现东西越写越多,这次就写硬件原理 驱动简介 驱动代码
下一节写 iic调试方式,内核iic框架分析(个人觉得这部分了解就好,因为不了解VFS 设备驱动总线不太好融会贯通)。
提示:以下是本篇文章正文内容,下面案例仅供参考 ,有任何问题欢迎指出。
具体这个协议怎么来的百度讲的很清楚,我就说一下i2c协议硬件上连线和对设备访问如何访问。
iic原理:
网上找了个图画的挺好,有三个设备 从机1 从机2 从机3; R 是上拉电阻 iic总线就是 SDA(串行数据总线) SCL(串行时钟总线),主控制芯片和从设备就通过SCL和SDA相连接;
既然Rp上拉电阻那么空闲时 SCL和SDA就是高电平;或者SCL SDA没有接从设备时也是高电平。
1、是怎么通过SCL SDA通信呢?
2、这么多从机,主控设备如何知道要和那个设备通信呢?
带着问题来看:
随便找个原理图看看: TI公司的TMP401温感芯片
芯片资料可以去官网下载: TMP401 数据表, 产品信息与支持 | TI.com.cn 第7节
根据原理图可以看到 SCL SDA 分别接在了 我们板子上的 I2C1_SCL I2C1_SDA,是板子上i2c总线;
一般芯片的datesheet 支持 IIC或者SPI都会有这么一节, Programming 这个就是介绍总线协议的,会包含读写时序图 起始结束等信号持续时间设置参数等等。
有一段话至关重要: 就是串行总线地址,其实就是你的设备地址啦。就像我们原理图上都已经写好了)0x4c,这个有什么用呢?
这样的,iic通信都是主控制器发起的,无论都还是写,我们写驱动预先会吧从设备的设备地址保存,当主控制器需要和指定的设备通信时就在总线上发送这个地址如(0x4c),那么所有的设备都会收到这个(0x4c)的数据,但是只有是0x4c的这个设备他才会给一个回应(术语ACK),这样就算和主控制器建立了链接,可以发送数据了。这就是我上面提到的时序图,来看看吧。
这个图就是写操作的时序图。可以看到 每一次主控制器和从机交互一共有九个时钟(字节)参与,
前1-7 表示设备的地址1001100 第8位读写位(1表示读 0 表示写),此时主控制器就发送完第一个字节数据,等待匹配的从机回应, 就是ACK BY Device 这一位是从设备发送的。如果匹配成功后,主控制发送第二个字节就是我们需要发送的数据,数据每个芯片不同可能是8位或者16位等,发送完后等待从机回应ACK。这就是一次数据传输了。当然数据又其实结束信号,这个对于单片机调试可能会用,对于linux调试一般比较少,看一下芯片手册时序图这个就能理解了。
上面的两个问题也就解释了,
1、是怎么通过SCL SDA通信呢?
由主控制器发起向从机发送地址,从机反馈回应,然后主控制在发送数据 ,从机回应 依次循环,直到接收到停止信号。停止信号 sda 从低到高的一个跳变沿表示。
2、这么多从机,主控设备如何知道要和那个设备通信呢?
通过主控设备发送从机的设备地址, 如果从机回复了ACK那么就算匹配成功。空闲时SCL和SDA都是高电平,当主机发送完地址后,主控制器会拉高SDA至于空闲状态,这个时候从设备的ACK会拉低总线那么其他设备就没办法操作了,一旦SDA被拉低就代表是忙碌状态。
以上是iic硬件或者基本的原理;
步骤:
1、配置设备树
2、注册iic设备驱动到内核 一般使用module_i2c_driver(static struct i2c_driver);
3、设置 struct i2c_driver 结构体和 设备树匹配
4、定义一个自己的结构体,在i2c_driver ->probe函数中分配空间和初始化。
5、多种方式
1-1、 注册一个字符设备,通过字符设备的 fops-> read write ioctl中实现对 设备的读写控制。
1-2、注册一个hwmon设备(一般用于温感等),通过内核提供的接口devm_hwmon_device_register_with_groups,在/sys/class/下创建属性文件,提供show store两个属性供用户空间访问。
1、module_i2c_driver(MY_IIC_DRV) 等于 定义入口出口函数
i2c_add_driver(MY_IIC_DRV); i2c_del_driver(MY_IIC_DRV);
2、 struct i2c_driver 向内核注册驱动的结构体。
static struct i2c_driver tmp401_driver = { .class = I2C_CLASS_HWMON, //所属类,如果不适用 hwmon 方式不写 .driver = { // 驱动,用来匹配设备树中定义的设备 .name = "tmp401", .of_match_table = of_match_ptr(tmp401_of_match), }, .probe = tmp401_probe, //设备和驱动匹配成功后调用这个函数 .id_table = tmp401_id, //用来初始化board_info .detect = tmp401_detect, //探测 设备是否存在,就是发送设备地址到总线各个设备 .address_list = normal_i2c, //存放 设备地址 };
3、我们需要实现 tmp401_probe tmp401_detect函数 如果使用字符设备实现读写的话大体框架如下,读写函数中实现对设备的操作即可。
struct IIC_myData{ struct i2c_client *client; // 发送和接受的接口在这里存放 struct mutex update_lock; //锁 u8 status; //一些标志状态 u8 data; // 读写数据 u8 flag; // }; struct IIC_myData * my_data; int major_ret ; static const struct file_operations capi_fops = { .owner = THIS_MODULE, .read = myiic_read, .write = myiic_write, .unlocked_ioctl = myiic_unlocked_ioctl, .open = myiic_open, .release = myiic_release, }; static int tmp401_probe(struct i2c_client *client, const struct i2c_device_id *id) { /* 分配自己定义的结构体 */ my_data = devm_kzalloc(client->dev, sizeof(struct IIC_myData), GFP_KERNEL); /* 初始化 */ my_data->client = client; mutex_init(&my_data->update_lock); ..... /* 注册字符设备 创建fops*/ major_ret = register_chrdev(0, "myiic", &myiic_fops); //创建设备类 myiic_class = class_create(THIS_MODULE, "myiicClass"); device_create(myiic_class, NULL, MKDEV(major_ret, 0), NULL, "myiicDev"); } /* 之后实现 读写 打开等函数即可 */
tmp401: tmp401@4c { /* u23 */ compatible = "ti,tmp401"; //用来和驱动匹配的名字 reg = <0x4c>; //设备地址 }; /* 环境温度 temp1_input */ lm75_4f: lm75@4f { compatible = "lm75"; reg = <0x4f>; };
使用第二种方式,使用HWMON方式实现
#include <linux/module.h> #include <linux/init.h> #include <linux/bitops.h> #include <linux/slab.h> #include <linux/jiffies.h> #include <linux/i2c.h> #include <linux/hwmon.h> #include <linux/hwmon-sysfs.h> #include <linux/err.h> #include <linux/mutex.h> #include <linux/sysfs.h> /* Addresses to scan */ static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4c, 0x4d, 0x4e, 0x4f, I2C_CLIENT_END }; enum chips { tmp401, tmp411, tmp431, tmp432, tmp435, tmp461 }; /* * The TMP401 registers, note some registers have different addresses for * reading and writing */ #define TMP401_STATUS 0x02 #define TMP401_CONFIG_READ 0x03 #define TMP401_CONFIG_WRITE 0x09 #define TMP401_CONVERSION_RATE_READ 0x04 #define TMP401_CONVERSION_RATE_WRITE 0x0A #define TMP401_TEMP_CRIT_HYST 0x21 #define TMP401_MANUFACTURER_ID_REG 0xFE #define TMP401_DEVICE_ID_REG 0xFF static const u8 TMP401_TEMP_MSB_READ[7][2] = { { 0x00, 0x01 }, /* temp */ { 0x06, 0x08 }, /* low limit */ { 0x05, 0x07 }, /* high limit */ { 0x20, 0x19 }, /* therm (crit) limit */ { 0x30, 0x34 }, /* lowest */ { 0x32, 0x36 }, /* highest */ { 0, 0x11 }, /* offset */ }; static const u8 TMP401_TEMP_MSB_WRITE[7][2] = { { 0, 0 }, /* temp (unused) */ { 0x0C, 0x0E }, /* low limit */ { 0x0B, 0x0D }, /* high limit */ { 0x20, 0x19 }, /* therm (crit) limit */ { 0x30, 0x34 }, /* lowest */ { 0x32, 0x36 }, /* highest */ { 0, 0x11 }, /* offset */ }; static const u8 TMP432_TEMP_MSB_READ[4][3] = { { 0x00, 0x01, 0x23 }, /* temp */ { 0x06, 0x08, 0x16 }, /* low limit */ { 0x05, 0x07, 0x15 }, /* high limit */ { 0x20, 0x19, 0x1A }, /* therm (crit) limit */ }; static const u8 TMP432_TEMP_MSB_WRITE[4][3] = { { 0, 0, 0 }, /* temp - unused */ { 0x0C, 0x0E, 0x16 }, /* low limit */ { 0x0B, 0x0D, 0x15 }, /* high limit */ { 0x20, 0x19, 0x1A }, /* therm (crit) limit */ }; /* [0] = fault, [1] = low, [2] = high, [3] = therm/crit */ static const u8 TMP432_STATUS_REG[] = { 0x1b, 0x36, 0x35, 0x37 }; /* Flags */ #define TMP401_CONFIG_RANGE BIT(2) #define TMP401_CONFIG_SHUTDOWN BIT(6) #define TMP401_STATUS_LOCAL_CRIT BIT(0) #define TMP401_STATUS_REMOTE_CRIT BIT(1) #define TMP401_STATUS_REMOTE_OPEN BIT(2) #define TMP401_STATUS_REMOTE_LOW BIT(3) #define TMP401_STATUS_REMOTE_HIGH BIT(4) #define TMP401_STATUS_LOCAL_LOW BIT(5) #define TMP401_STATUS_LOCAL_HIGH BIT(6) /* On TMP432, each status has its own register */ #define TMP432_STATUS_LOCAL BIT(0) #define TMP432_STATUS_REMOTE1 BIT(1) #define TMP432_STATUS_REMOTE2 BIT(2) /* Manufacturer / Device ID's */ #define TMP401_MANUFACTURER_ID 0x55 #define TMP401_DEVICE_ID 0x11 #define TMP411A_DEVICE_ID 0x12 #define TMP411B_DEVICE_ID 0x13 #define TMP411C_DEVICE_ID 0x10 #define TMP431_DEVICE_ID 0x31 #define TMP432_DEVICE_ID 0x32 #define TMP435_DEVICE_ID 0x35 /* * Driver data (common to all clients) */ static const struct i2c_device_id tmp401_id[] = { { "tmp401", tmp401 }, { "tmp411", tmp411 }, { "tmp431", tmp431 }, { "tmp432", tmp432 }, { "tmp435", tmp435 }, { "tmp461", tmp461 }, { } }; MODULE_DEVICE_TABLE(i2c, tmp401_id); static const struct of_device_id tmp401_of_match[] = { { .compatible = "ti,tmp401", //这个是匹配设备树中的compatible字段,要保持一致 .data = (void *)tmp401 //私有数据; }, { }, }; MODULE_DEVICE_TABLE(of, tmp401_of_match); /* * Client data (each client gets its own) */ struct tmp401_data { struct i2c_client *client; const struct attribute_group *groups[3]; struct mutex update_lock; char valid; /* zero until following fields are valid */ unsigned long last_updated; /* in jiffies */ enum chips kind; unsigned int update_interval; /* in milliseconds */ /* register values */ u8 status[4]; u8 config; u16 temp[7][3]; u8 temp_crit_hyst; }; /* * Sysfs attr show / store functions */ static int tmp401_register_to_temp(u16 reg, u8 config) { int temp = reg; if (config & TMP401_CONFIG_RANGE) //正负温度 测量范围不同区分 temp -= 64 * 256; return DIV_ROUND_CLOSEST(temp * 125, 32); } static u16 tmp401_temp_to_register(long temp, u8 config, int zbits) { if (config & TMP401_CONFIG_RANGE) { temp = clamp_val(temp, -64000, 191000); temp += 64000; } else temp = clamp_val(temp, 0, 127000); return DIV_ROUND_CLOSEST(temp * (1 << (8 - zbits)), 1000) << zbits; } //实现温度读取 读取温度的寄存器地址存放在TMP401_TEMP_MSB_READ TMP432_TEMP_MSB_READ 数组中 static int tmp401_update_device_reg16(struct i2c_client *client, struct tmp401_data *data) { int i, j, val; int num_regs = data->kind == tmp411 ? 6 : 4; int num_sensors = data->kind == tmp432 ? 3 : 2; for (i = 0; i < num_sensors; i++) { /* local / r1 / r2 */ for (j = 0; j < num_regs; j++) { /* temp / low / ... */ u8 regaddr; regaddr = data->kind == tmp432 ? TMP432_TEMP_MSB_READ[j][i] : TMP401_TEMP_MSB_READ[j][i]; if (j == 3) { /* crit is msb only */ val = i2c_smbus_read_byte_data(client, regaddr); } else { val = i2c_smbus_read_word_swapped(client, regaddr); } if (val < 0) return val; data->temp[j][i] = j == 3 ? val << 8 : val; } } return 0; } static struct tmp401_data *tmp401_update_device(struct device *dev) { struct tmp401_data *data = dev_get_drvdata(dev); struct i2c_client *client = data->client; struct tmp401_data *ret = data; int i, val; unsigned long next_update; mutex_lock(&data->update_lock); next_update = data->last_updated + msecs_to_jiffies(data->update_interval); if (time_after(jiffies, next_update) || !data->valid) { if (data->kind != tmp432) { /* * The driver uses the TMP432 status format internally. * Convert status to TMP432 format for other chips. */ val = i2c_smbus_read_byte_data(client, TMP401_STATUS); if (val < 0) { ret = ERR_PTR(val); goto abort; } data->status[0] = (val & TMP401_STATUS_REMOTE_OPEN) >> 1; data->status[1] = ((val & TMP401_STATUS_REMOTE_LOW) >> 2) | ((val & TMP401_STATUS_LOCAL_LOW) >> 5); data->status[2] = ((val & TMP401_STATUS_REMOTE_HIGH) >> 3) | ((val & TMP401_STATUS_LOCAL_HIGH) >> 6); data->status[3] = val & (TMP401_STATUS_LOCAL_CRIT | TMP401_STATUS_REMOTE_CRIT); } else { for (i = 0; i < ARRAY_SIZE(data->status); i++) { val = i2c_smbus_read_byte_data(client, TMP432_STATUS_REG[i]); if (val < 0) { ret = ERR_PTR(val); goto abort; } data->status[i] = val; } } val = i2c_smbus_read_byte_data(client, TMP401_CONFIG_READ); if (val < 0) { ret = ERR_PTR(val); goto abort; } data->config = val; val = tmp401_update_device_reg16(client, data); if (val < 0) { ret = ERR_PTR(val); goto abort; } val = i2c_smbus_read_byte_data(client, TMP401_TEMP_CRIT_HYST); if (val < 0) { ret = ERR_PTR(val); goto abort; } data->temp_crit_hyst = val; data->last_updated = jiffies; data->valid = 1; } abort: mutex_unlock(&data->update_lock); return ret; } static ssize_t show_temp(struct device *dev, struct device_attribute *devattr, char *buf) { //SENSOR_DEVICE_ATTR_2(0, 0);最后两个参数表示nr 和index int nr = to_sensor_dev_attr_2(devattr)->nr; int index = to_sensor_dev_attr_2(devattr)->index; struct tmp401_data *data = tmp401_update_device(dev); if (IS_ERR(data)) return PTR_ERR(data); return sprintf(buf, "%d\n", tmp401_register_to_temp(data->temp[nr][index], data->config)); } static ssize_t show_temp_crit_hyst(struct device *dev, struct device_attribute *devattr, char *buf) { int temp, index = to_sensor_dev_attr(devattr)->index; struct tmp401_data *data = tmp401_update_device(dev); if (IS_ERR(data)) return PTR_ERR(data); mutex_lock(&data->update_lock); temp = tmp401_register_to_temp(data->temp[3][index], data->config); temp -= data->temp_crit_hyst * 1000; mutex_unlock(&data->update_lock); return sprintf(buf, "%d\n", temp); } static ssize_t show_status(struct device *dev, struct device_attribute *devattr, char *buf) { int nr = to_sensor_dev_attr_2(devattr)->nr; int mask = to_sensor_dev_attr_2(devattr)->index; struct tmp401_data *data = tmp401_update_device(dev); if (IS_ERR(data)) return PTR_ERR(data); return sprintf(buf, "%d\n", !!(data->status[nr] & mask)); } static ssize_t store_temp(struct device *dev, struct device_attribute *devattr, const char *buf, size_t count) { int nr = to_sensor_dev_attr_2(devattr)->nr; int index = to_sensor_dev_attr_2(devattr)->index; struct tmp401_data *data = dev_get_drvdata(dev); struct i2c_client *client = data->client; long val; u16 reg; u8 regaddr; if (kstrtol(buf, 10, &val)) return -EINVAL; reg = tmp401_temp_to_register(val, data->config, nr == 3 ? 8 : 4); mutex_lock(&data->update_lock); regaddr = data->kind == tmp432 ? TMP432_TEMP_MSB_WRITE[nr][index] : TMP401_TEMP_MSB_WRITE[nr][index]; if (nr == 3) { /* crit is msb only */ i2c_smbus_write_byte_data(client, regaddr, reg >> 8); } else { /* Hardware expects big endian data --> use _swapped */ i2c_smbus_write_word_swapped(client, regaddr, reg); } data->temp[nr][index] = reg; mutex_unlock(&data->update_lock); return count; } static ssize_t store_temp_crit_hyst(struct device *dev, struct device_attribute *devattr, const char *buf, size_t count) { int temp, index = to_sensor_dev_attr(devattr)->index; struct tmp401_data *data = tmp401_update_device(dev); long val; u8 reg; if (IS_ERR(data)) return PTR_ERR(data); if (kstrtol(buf, 10, &val)) return -EINVAL; if (data->config & TMP401_CONFIG_RANGE) val = clamp_val(val, -64000, 191000); else val = clamp_val(val, 0, 127000); mutex_lock(&data->update_lock); temp = tmp401_register_to_temp(data->temp[3][index], data->config); val = clamp_val(val, temp - 255000, temp); reg = ((temp - val) + 500) / 1000; i2c_smbus_write_byte_data(data->client, TMP401_TEMP_CRIT_HYST, reg); data->temp_crit_hyst = reg; mutex_unlock(&data->update_lock); return count; } /* * Resets the historical measurements of minimum and maximum temperatures. * This is done by writing any value to any of the minimum/maximum registers * (0x30-0x37). */ static ssize_t reset_temp_history(struct device *dev, struct device_attribute *devattr, const char *buf, size_t count) { struct tmp401_data *data = dev_get_drvdata(dev); struct i2c_client *client = data->client; long val; if (kstrtol(buf, 10, &val)) return -EINVAL; if (val != 1) { dev_err(dev, "temp_reset_history value %ld not supported. Use 1 to reset the history!\n", val); return -EINVAL; } mutex_lock(&data->update_lock); i2c_smbus_write_byte_data(client, TMP401_TEMP_MSB_WRITE[5][0], val); data->valid = 0; mutex_unlock(&data->update_lock); return count; } static ssize_t update_interval_show(struct device *dev, struct device_attribute *attr, char *buf) { struct tmp401_data *data = dev_get_drvdata(dev); return sprintf(buf, "%u\n", data->update_interval); } static ssize_t update_interval_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { struct tmp401_data *data = dev_get_drvdata(dev); struct i2c_client *client = data->client; unsigned long val; int err, rate; err = kstrtoul(buf, 10, &val); if (err) return err; /* * For valid rates, interval can be calculated as * interval = (1 << (7 - rate)) * 125; * Rounded rate is therefore * rate = 7 - __fls(interval * 4 / (125 * 3)); * Use clamp_val() to avoid overflows, and to ensure valid input * for __fls. */ val = clamp_val(val, 125, 16000); rate = 7 - __fls(val * 4 / (125 * 3)); mutex_lock(&data->update_lock); i2c_smbus_write_byte_data(client, TMP401_CONVERSION_RATE_WRITE, rate); data->update_interval = (1 << (7 - rate)) * 125; mutex_unlock(&data->update_lock); return count; } static SENSOR_DEVICE_ATTR_2(temp1_input, S_IRUGO, show_temp, NULL, 0, 0); static SENSOR_DEVICE_ATTR_2(temp1_min, S_IWUSR | S_IRUGO, show_temp, store_temp, 1, 0); static SENSOR_DEVICE_ATTR_2(temp1_max, S_IWUSR | S_IRUGO, show_temp, store_temp, 2, 0); static SENSOR_DEVICE_ATTR_2(temp1_crit, S_IWUSR | S_IRUGO, show_temp, store_temp, 3, 0); static SENSOR_DEVICE_ATTR(temp1_crit_hyst, S_IWUSR | S_IRUGO, show_temp_crit_hyst, store_temp_crit_hyst, 0); static SENSOR_DEVICE_ATTR_2(temp1_min_alarm, S_IRUGO, show_status, NULL, 1, TMP432_STATUS_LOCAL); static SENSOR_DEVICE_ATTR_2(temp1_max_alarm, S_IRUGO, show_status, NULL, 2, TMP432_STATUS_LOCAL); static SENSOR_DEVICE_ATTR_2(temp1_crit_alarm, S_IRUGO, show_status, NULL, 3, TMP432_STATUS_LOCAL); static SENSOR_DEVICE_ATTR_2(temp2_input, S_IRUGO, show_temp, NULL, 0, 1); static SENSOR_DEVICE_ATTR_2(temp2_min, S_IWUSR | S_IRUGO, show_temp, store_temp, 1, 1); static SENSOR_DEVICE_ATTR_2(temp2_max, S_IWUSR | S_IRUGO, show_temp, store_temp, 2, 1); static SENSOR_DEVICE_ATTR_2(temp2_crit, S_IWUSR | S_IRUGO, show_temp, store_temp, 3, 1); static SENSOR_DEVICE_ATTR(temp2_crit_hyst, S_IRUGO, show_temp_crit_hyst, NULL, 1); static SENSOR_DEVICE_ATTR_2(temp2_fault, S_IRUGO, show_status, NULL, 0, TMP432_STATUS_REMOTE1); static SENSOR_DEVICE_ATTR_2(temp2_min_alarm, S_IRUGO, show_status, NULL, 1, TMP432_STATUS_REMOTE1); static SENSOR_DEVICE_ATTR_2(temp2_max_alarm, S_IRUGO, show_status, NULL, 2, TMP432_STATUS_REMOTE1); static SENSOR_DEVICE_ATTR_2(temp2_crit_alarm, S_IRUGO, show_status, NULL, 3, TMP432_STATUS_REMOTE1); static DEVICE_ATTR_RW(update_interval); static struct attribute *tmp401_attributes[] = { &sensor_dev_attr_temp1_input.dev_attr.attr, &sensor_dev_attr_temp1_min.dev_attr.attr, &sensor_dev_attr_temp1_max.dev_attr.attr, &sensor_dev_attr_temp1_crit.dev_attr.attr, &sensor_dev_attr_temp1_crit_hyst.dev_attr.attr, &sensor_dev_attr_temp1_max_alarm.dev_attr.attr, &sensor_dev_attr_temp1_min_alarm.dev_attr.attr, &sensor_dev_attr_temp1_crit_alarm.dev_attr.attr, &sensor_dev_attr_temp2_input.dev_attr.attr, &sensor_dev_attr_temp2_min.dev_attr.attr, &sensor_dev_attr_temp2_max.dev_attr.attr, &sensor_dev_attr_temp2_crit.dev_attr.attr, &sensor_dev_attr_temp2_crit_hyst.dev_attr.attr, &sensor_dev_attr_temp2_fault.dev_attr.attr, &sensor_dev_attr_temp2_max_alarm.dev_attr.attr, &sensor_dev_attr_temp2_min_alarm.dev_attr.attr, &sensor_dev_attr_temp2_crit_alarm.dev_attr.attr, &dev_attr_update_interval.attr, NULL }; static const struct attribute_group tmp401_group = { .attrs = tmp401_attributes, }; /* * Additional features of the TMP411 chip. * The TMP411 stores the minimum and maximum * temperature measured since power-on, chip-reset, or * minimum and maximum register reset for both the local * and remote channels. */ static SENSOR_DEVICE_ATTR_2(temp1_lowest, S_IRUGO, show_temp, NULL, 4, 0); static SENSOR_DEVICE_ATTR_2(temp1_highest, S_IRUGO, show_temp, NULL, 5, 0); static SENSOR_DEVICE_ATTR_2(temp2_lowest, S_IRUGO, show_temp, NULL, 4, 1); static SENSOR_DEVICE_ATTR_2(temp2_highest, S_IRUGO, show_temp, NULL, 5, 1); static SENSOR_DEVICE_ATTR(temp_reset_history, S_IWUSR, NULL, reset_temp_history, 0); static struct attribute *tmp411_attributes[] = { &sensor_dev_attr_temp1_highest.dev_attr.attr, &sensor_dev_attr_temp1_lowest.dev_attr.attr, &sensor_dev_attr_temp2_highest.dev_attr.attr, &sensor_dev_attr_temp2_lowest.dev_attr.attr, &sensor_dev_attr_temp_reset_history.dev_attr.attr, NULL }; static const struct attribute_group tmp411_group = { .attrs = tmp411_attributes, }; static SENSOR_DEVICE_ATTR_2(temp3_input, S_IRUGO, show_temp, NULL, 0, 2); static SENSOR_DEVICE_ATTR_2(temp3_min, S_IWUSR | S_IRUGO, show_temp, store_temp, 1, 2); static SENSOR_DEVICE_ATTR_2(temp3_max, S_IWUSR | S_IRUGO, show_temp, store_temp, 2, 2); static SENSOR_DEVICE_ATTR_2(temp3_crit, S_IWUSR | S_IRUGO, show_temp, store_temp, 3, 2); static SENSOR_DEVICE_ATTR(temp3_crit_hyst, S_IRUGO, show_temp_crit_hyst, NULL, 2); static SENSOR_DEVICE_ATTR_2(temp3_fault, S_IRUGO, show_status, NULL, 0, TMP432_STATUS_REMOTE2); static SENSOR_DEVICE_ATTR_2(temp3_min_alarm, S_IRUGO, show_status, NULL, 1, TMP432_STATUS_REMOTE2); static SENSOR_DEVICE_ATTR_2(temp3_max_alarm, S_IRUGO, show_status, NULL, 2, TMP432_STATUS_REMOTE2); static SENSOR_DEVICE_ATTR_2(temp3_crit_alarm, S_IRUGO, show_status, NULL, 3, TMP432_STATUS_REMOTE2); static struct attribute *tmp432_attributes[] = { &sensor_dev_attr_temp3_input.dev_attr.attr, &sensor_dev_attr_temp3_min.dev_attr.attr, &sensor_dev_attr_temp3_max.dev_attr.attr, &sensor_dev_attr_temp3_crit.dev_attr.attr, &sensor_dev_attr_temp3_crit_hyst.dev_attr.attr, &sensor_dev_attr_temp3_fault.dev_attr.attr, &sensor_dev_attr_temp3_max_alarm.dev_attr.attr, &sensor_dev_attr_temp3_min_alarm.dev_attr.attr, &sensor_dev_attr_temp3_crit_alarm.dev_attr.attr, NULL }; static const struct attribute_group tmp432_group = { .attrs = tmp432_attributes, }; /* * Additional features of the TMP461 chip. * The TMP461 temperature offset for the remote channel. * show_temp 实现读取 store_temp实现存储 */ static SENSOR_DEVICE_ATTR_2(temp2_offset, S_IWUSR | S_IRUGO, show_temp, store_temp, 6, 1); //创建属性列表 static struct attribute *tmp461_attributes[] = { &sensor_dev_attr_temp2_offset.dev_attr.attr, NULL }; //属性创建组 static const struct attribute_group tmp461_group = { .attrs = tmp461_attributes, }; /* * Begin non sysfs callback code (aka Real code) */ static int tmp401_init_client(struct tmp401_data *data, struct i2c_client *client) { int config, config_orig, status = 0; /* Set the conversion rate to 2 Hz */ i2c_smbus_write_byte_data(client, TMP401_CONVERSION_RATE_WRITE, 5); data->update_interval = 500; /* Start conversions (disable shutdown if necessary) */ config = i2c_smbus_read_byte_data(client, TMP401_CONFIG_READ); if (config < 0) return config; config_orig = config; config &= ~TMP401_CONFIG_SHUTDOWN; config |= (1<<2); //修改测量范围 默认只能测量正温度 if (config != config_orig) status = i2c_smbus_write_byte_data(client, TMP401_CONFIG_WRITE, config); return status; } static int tmp401_detect(struct i2c_client *client, struct i2c_board_info *info) { enum chips kind; //i2c_adapter 这个结构很重要是在注册设备是定义这个结构,包含了算法和锁得操作 struct i2c_adapter *adapter = client->adapter; u8 reg; if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA)) return -ENODEV; /* Detect and identify the chip */ reg = i2c_smbus_read_byte_data(client, TMP401_MANUFACTURER_ID_REG); if (reg != TMP401_MANUFACTURER_ID) return -ENODEV; reg = i2c_smbus_read_byte_data(client, TMP401_DEVICE_ID_REG); switch (reg) { case TMP401_DEVICE_ID: if (client->addr != 0x4c) return -ENODEV; kind = tmp401; break; case TMP411A_DEVICE_ID: if (client->addr != 0x4c) return -ENODEV; kind = tmp411; break; case TMP411B_DEVICE_ID: if (client->addr != 0x4d) return -ENODEV; kind = tmp411; break; case TMP411C_DEVICE_ID: if (client->addr != 0x4e) return -ENODEV; kind = tmp411; break; case TMP431_DEVICE_ID: if (client->addr != 0x4c && client->addr != 0x4d) return -ENODEV; kind = tmp431; break; case TMP432_DEVICE_ID: if (client->addr != 0x4c && client->addr != 0x4d) return -ENODEV; kind = tmp432; break; case TMP435_DEVICE_ID: kind = tmp435; break; default: return -ENODEV; } reg = i2c_smbus_read_byte_data(client, TMP401_CONFIG_READ); if (reg & 0x1b) return -ENODEV; reg = i2c_smbus_read_byte_data(client, TMP401_CONVERSION_RATE_READ); /* Datasheet says: 0x1-0x6 */ if (reg > 15) return -ENODEV; strlcpy(info->type, tmp401_id[kind].name, I2C_NAME_SIZE); return 0; } static int tmp401_probe(struct i2c_client *client, const struct i2c_device_id *id) { static const char * const names[] = { "TMP401", "TMP411", "TMP431", "TMP432", "TMP435", "TMP461" }; struct device *dev = &client->dev; struct device *hwmon_dev; struct tmp401_data *data; int groups = 0, status; //给私有数据分配空间 data = devm_kzalloc(dev, sizeof(struct tmp401_data), GFP_KERNEL); if (!data) return -ENOMEM; //初始化私有数据 和锁 data->client = client; mutex_init(&data->update_lock); data->kind = id->driver_data; /* Initialize the TMP401 chip */ status = tmp401_init_client(data, client); if (status < 0) return status; /* Register sysfs hooks */ data->groups[groups++] = &tmp401_group; /* Register additional tmp411 sysfs hooks */ if (data->kind == tmp411) data->groups[groups++] = &tmp411_group; /* Register additional tmp432 sysfs hooks */ if (data->kind == tmp432) data->groups[groups++] = &tmp432_group; if (data->kind == tmp461) data->groups[groups++] = &tmp461_group; //注册HWMON设备 创建属性文件 hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name, data, data->groups); if (IS_ERR(hwmon_dev)) return PTR_ERR(hwmon_dev); dev_info(dev, "Detected TI %s chip\n", names[data->kind]); return 0; } //定义一个iic驱动结构 static struct i2c_driver tmp401_driver = { //声明hwmon类i2c.h中还定义了 I2C_CLASS_DDC I2C_CLASS_SPD .class = I2C_CLASS_HWMON, .driver = { .name = "tmp401", //驱动名称就不说了 .of_match_table = of_match_ptr(tmp401_of_match), }, .probe = tmp401_probe, .id_table = tmp401_id, //多个设备的时候来存放设备设备名列表 .detect = tmp401_detect, //探测函数,调用probe之前先发送设备地址到总线上等待从机反馈 .address_list = normal_i2c, //存放从机设备地址列表 比如0x4c }; module_i2c_driver(tmp401_driver);
篇幅有点长,本次掌握iic使用方式。内核中如何初始化设备树中iic设备 还有如何使得设备和驱动匹配调用probe函数的分析放在下一小节中分析。