系列文章目录
1、linux i2c 驱动一
2、linux i2c 驱动二
目录
前言
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。
一、i2c协议简述
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；
二、linux 下 i2c驱动框架
1.首先掌握如何使用
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。
2.理解原理
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 */
三、实例
1、设备树
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>;
};2、驱动代码
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);
总结
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。