Linux-IIC驱动(详解)

struct i2c_adapter adap;static int s3c24xx_i2c_probe(struct platform_device *pdev)
{
struct s3c24xx_i2c *i2c = &s3c24xx_i2c;
... ... /*获取,使能I2C时钟*/
i2c->clk = clk_get(&pdev->dev, "i2c"); //获取i2c时钟
clk_enable(i2c->clk); //使能i2c时钟 ... ....
/*获取资源*/
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
i2c->regs = ioremap(res->start, (res->end-res->start)+1); ... .... /*设置i2c_adapter适配器结构体, 将i2c结构体设为adap的私有数据成员*/
i2c->adap.algo_data = i2c; //i2c_adapter适配器指向s3c24xx_i2c;
i2c->adap.dev.parent = &pdev->dev;/* initialise the i2c controller */
/*初始化2440的I2C相关的寄存器*/
ret = s3c24xx_i2c_init(i2c);
if (ret != 0)
goto err_iomap; ... ...
/*注册中断服务函数*/
ret = request_irq(res->start, s3c24xx_i2c_irq, IRQF_DISABLED,pdev->name, i2c);
... ... /*注册i2c_adapter适配器结构体*/
ret = i2c_add_adapter(&i2c->adap);
... ...
}

int i2c_add_adapter(struct i2c_adapter *adapter)
{
int id, res = 0;retry:
if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0) //调用idr_pre_get()为i2c_adapter预留内存空间
return -ENOMEM; mutex_lock(&core_lists); /* "above" here means "above or equal to", sigh */
res = idr_get_new_above(&i2c_adapter_idr, adapter,__i2c_first_dynamic_bus_num, &id);
//调用idr_get_new_above()将结构插入i2c_adapter_idr中,并将插入的位置赋给id,以后可以通过id在i2c_adapter_idr中找到相应的i2c_adapter结构体 mutex_unlock(&core_lists); if (res < 0) {
if (res == -EAGAIN)
goto retry;
return res;
}
adapter->nr = id;
return i2c_register_adapter(adapter); //调用i2c_register_adapter()函数进一步来注册.
}

static int i2c_register_adapter(struct i2c_adapter *adap)
{
struct list_head *item; //链表头,用来存放i2c_driver结构体的表头
struct i2c_driver *driver; //i2c_driver,用来描述一个IIC设备驱动
list_add_tail(&adap->list, &adapters); //添加到内核的adapter链表中
... ...
list_for_each(item,&drivers) { //for循环,从drivers链表里找到i2c_driver结构体的表头
driver = list_entry(item, struct i2c_driver, list); //通过list_head表头,找到i2c_driver结构体
if (driver->attach_adapter)
/* We ignore the return code; if it fails, too bad */
driver->attach_adapter(adap);
//调用i2c_driver的attach_adapter函数来看看,这个新注册的设配器是否支持i2c_driver }
}

struct i2c_adapter { struct module *owner;//所属模块
unsigned int id;//algorithm的类型，定义于i2c-id.h,
unsigned int class;
const struct i2c_algorithm *algo; //总线通信方法结构体指针
void *algo_data; //algorithm数据
struct rt_mutex bus_lock;//控制并发访问的自旋锁
int timeout;
int retries;//重试次数
struct device dev; //适配器设备
int nr; //存放在i2c_adapter_idr里的位置号
char name[48];//适配器名称
struct completion dev_released;//用于同步
struct list_head userspace_clients; //client链表头 };

static const struct i2c_algorithm s3c24xx_i2c_algorithm = {
.master_xfer = s3c24xx_i2c_xfer, //主机传输
.functionality = s3c24xx_i2c_func,
};static struct s3c24xx_i2c s3c24xx_i2c = {
.lock = __SPIN_LOCK_UNLOCKED(s3c24xx_i2c.lock),
.wait = __WAIT_QUEUE_HEAD_INITIALIZER(s3c24xx_i2c.wait),
.tx_setup = 50, //用来延时,等待SCL被释放
.adap = { // i2c_adapter适配器结构体
.name = "s3c2410-i2c",
.owner = THIS_MODULE,
.algo = &s3c24xx_i2c_algorithm, //存放i2c_algorithm算法结构体
.retries = 2, //重试次数
.class = I2C_CLASS_HWMON,
},
};

static void s3c24xx_i2c_message_start(struct s3c24xx_i2c *i2c, struct i2c_msg *msg)
{ unsigned int addr = (msg->addr & 0x7f) << 1; //IIC从设备地址的最低位为读写标志位
... ... stat = 0;
stat |= S3C2410_IICSTAT_TXRXEN; //设置标志位启动IIC收发使能 if (msg->flags & I2C_M_RD) { //判断是读,还是写
stat |= S3C2410_IICSTAT_MASTER_RX;
addr |= 1; //设置从IIC设备地址为读标志
} else
stat |= S3C2410_IICSTAT_MASTER_TX; s3c24xx_i2c_enable_ack(i2c); //使能ACK信号iiccon = readl(i2c->regs + S3C2410_IICCON); //读出IICCON寄存器 writel(stat, i2c->regs + S3C2410_IICSTAT); //写入IICSTAT寄存器,使能IIC的读或写标志 dev_dbg(i2c->dev, "START: %08lx to IICSTAT, %02x to DS\n", stat, addr); writeb(addr, i2c->regs + S3C2410_IICDS); //将IIC从设备地址写入IICDS寄存器 /* delay here to ensure the data byte has gotten onto the bus
* before the transaction is started */ ndelay(i2c->tx_setup); //延时,等待SCL被释放,下面便可以发送起始信号+IIC设备地址值 dev_dbg(i2c->dev, "iiccon, %08lx\n", iiccon);
writel(iiccon, i2c->regs + S3C2410_IICCON); stat |= S3C2410_IICSTAT_START;
writel(stat, i2c->regs + S3C2410_IICSTAT);
//设置IICSTAT寄存器的bit5=1,开始发送起始信号+IIC从设备地址值,并回应ACK
}

static struct i2c_driver eeprom_driver = {
.driver = {
.name = "eeprom", //名称
},
.id = I2C_DRIVERID_EEPROM, //IIC设备标识ID
.attach_adapter = eeprom_attach_adapter, //用来与总线驱动的适配器匹配,匹配成功添加到适配器adapter中
.detach_client = eeprom_detach_client, //与总线驱动的适配器解绑,分离这个IIC从设备
};

int i2c_add_driver(struct module *owner, struct i2c_driver *driver)
{
driver->driver.owner = owner;
driver->driver.bus = &i2c_bus_type; //将i2c_driver放在i2c_bus_type链表中 res = driver_register(&driver->driver); //注册一个i2c_driver
... ... if (driver->attach_adapter) {
struct i2c_adapter *adapter; //定义一个i2c_adapter适配器
list_for_each_entry(adapter, &adapters, list) //for循环提取出adapters链表中所有的i2c_adapter适配器,放入到adapter结构体中
{
driver->attach_adapter(adapter); //来匹配取出来的i2c_adapter适配器
}
}
... ...
return 0;
}

struct i2c_client_address_data {
unsigned short *normal_i2c; //存放正常的设备高7位地址数据
unsigned short *probe; //存放不受*ignore影响的高7位设备地址数据
unsigned short *ignore; //存放*ignore的高7位设备地址数据
unsigned short **forces; //forces表示适配器匹配不了该设备,也要将其放入适配器中};

#define AT24C02_ADDR (0xA0>>1) //AT24C02地址static unsigned short ignore[] = { I2C_CLIENT_END };
static unsigned short normal_addr[] = { AT24C02_ADDR, I2C_CLIENT_END };
static unsigned short force_addr[] = {ANY_I2C_BUS, AT24C02_ADDR ,2C_CLIENT_END};
static unsigned short * forces[] = {force_addr, NULL};
//ANY_I2C_BUS:表示支持所有适配器总线,若填指定的适配器总线ID,则表示该设备只支持指定的那个适配器static struct i2c_client_address_data addr_data = {
.normal_i2c = normal_addr, //存放at24c02地址
.probe = ignore, //表示无地址
.ignore = ignore, //表示无地址
. forces = forces, //存放强制的at24c02地址,表示强制支持};

int i2c_probe(struct i2c_adapter *adapter,struct i2c_client_address_data *address_data,int (*found_proc) (struct i2c_adapter *, int, int))
{
... ...
err = i2c_probe_address(adapter,forces[kind][i + 1],kind, found_proc);
}

static int i2c_probe_address(struct i2c_adapter *adapter, int addr, int kind,int (*found_proc) (struct i2c_adapter *, int, int))
{ /*判断设备地址是否有效,addr里存放的是设备地址前7位,比如AT24C02=0xA0,那么addr=0x50*/
if (addr < 0x03 || addr > 0x77) {
dev_warn(&adapter->dev, "Invalid probe address 0x%02x\n",addr); //打印地址无效,并退出
return -EINVAL;
} /*查找链表中其它IIC设备的设备地址,若这个设备地址已经被使用,则return*/
if (i2c_check_addr(adapter, addr))
return 0; if (kind < 0) {
if (i2c_smbus_xfer(adapter, addr, 0, 0, 0,I2C_SMBUS_QUICK, NULL) < 0) //进入I2C传输函数
return 0;
... ...
}

s32 i2c_smbus_xfer(struct i2c_adapter * adapter, u16 addr, unsigned short flags,char read_write, u8 command, int size,union i2c_smbus_data * data)
{
s32 res; flags &= I2C_M_TEN | I2C_CLIENT_PEC; if (adapter->algo->smbus_xfer) { //如果adapter适配器有smbus_xfer这个函数
mutex_lock(&adapter->bus_lock); //加互斥锁
res = adapter->algo->smbus_xfer(adapter,addr,flags,read_write,command,size,data);
//调用adapter适配器里的传输函数
mutex_unlock(&adapter->bus_lock); //解互斥锁
} else //否则使用默认函数传输设备地址
res = i2c_smbus_xfer_emulated(adapter,addr,flags,read_write,command,size,data);
return res;
}

static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,unsigned short flags,char read_write, u8 command, int size, union i2c_smbus_data * data)
{
unsigned char msgbuf0[I2C_SMBUS_BLOCK_MAX+3]; //属于 msg[0]的buf成员
unsigned char msgbuf1[I2C_SMBUS_BLOCK_MAX+2]; //属于 msg[1]的buf成员
int num = read_write == I2C_SMBUS_READ?2:1; //如果为读命令,就等于2,表示要执行两次数据传输
struct i2c_msg msg[2] = { { addr, flags, 1, msgbuf0 },
{ addr, flags | I2C_M_RD, 0, msgbuf1 }}; //定义两个i2c_msg结构体, msgbuf0[0] = command; //IIC设备地址最低位为读写命令
... ...
if (i2c_transfer(adapter, msg, num) < 0)
return -1; /*设置i2c_msg结构体成员*/
if (read_write == I2C_SMBUS_READ)
switch(size) {
... ...
case I2C_SMBUS_BYTE_DATA: //如果是读字节
if (read_write == I2C_SMBUS_READ)
msg[1].len = 1;
else {
msg[0].len = 2;
msgbuf0[1] = data->byte;
}
break;
... ...
}
... ... if (i2c_transfer(adapter, msg, num) < 0) //将 i2c_msg结构体的内容发送给I2C设备
return -1;
... ...
}

struct i2c_msg {
__u16 addr; //I2C从机的设备地址
__u16 flags; //当flags=0表示写, flags= I2C_M_RD表示读
__u16 len; //传输的数据长度,等于buf数组里的字节数
__u8 *buf; //存放数据的数组
};

struct i2c_client { unsigned short flags；//标志 unsigned short addr; //该i2c从设备的设备地址,存放地址高7位 char name[I2C_NAME_SIZE]; //设备名字 struct i2c_adapter *adapter;//依附的i2c_adapter,表示该IIC设备支持哪个适配器 struct i2c_driver *driver;//依附的i2c_driver ,表示该IIC从设备的驱动是哪个 struct device dev;//设备结构体 int irq;//设备所使用的结构体 struct list_head detected;//链表头 };

static int eeprom_detect(struct i2c_adapter *adapter, int address, int kind)
{
struct i2c_client *new_client; //定义一个i2c_client结构体局部变量new_client =kzalloc(sizeof(struct i2c_client), GFP_KERNEL); //分配i2c_client结构体为全局变量/*设置i2c_client结构体*/
new_client->addr = address; //设置设备地址
new_client->adapter = adapter; //设置依附的i2c_adapter
new_client->driver = &eeprom_driver; //设置依附的i2c_driver
new_client->flags = 0; //设置标志位为初始值
strlcpy(new_client->name, "eeprom", I2C_NAME_SIZE); //设置名字 /*注册i2c_client*/
if ((err = i2c_attach_client(new_client)))
goto exit_kfree; //注册失败,便释放i2c_client这个全局变量
... ...
exit_kfree:
kfree(new_client);
exit:
return err;
}

/*
* I2C-24C02
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/jiffies.h>
#include <linux/i2c.h>
#include <linux/mutex.h>
#include <linux/fs.h>
#include <asm/uaccess.h>static struct i2c_client *at24c02_client; //从设备结构体
static struct class *at24c02_class; //类结构体
static unsigned int at24c02_major; /*1.定义file_operations结构体 ,
* 设置字符设备的读写函数(实现对24C02的读写操作)
*/
static ssize_t at24c02_read(struct file *file, char __user *buf, size_t size, loff_t * offset)
{
struct i2c_msg msg[2];
u8 addr;
u8 data;
int ret; if(size!=1)
return -EINVAL; copy_from_user(&addr,buf,1); //获取读地址 msg[0].addr=at24c02_client->addr;
msg[0].flags=0; //写标志
msg[0].len =1;
msg[0].buf =&addr; //写入要读的地址 msg[1].addr=at24c02_client->addr;
msg[1].flags=I2C_M_RD; //读标志
msg[1].len =1;
msg[1].buf =&data; //读出数据 ret=i2c_transfer(at24c02_client->adapter, msg, 2);
if(ret==2) //表示2个msg传输成功
{
copy_to_user(buf,&data,1); //上传数据
return 0;
}
else
return -EAGAIN;
}static ssize_t at24c02_write(struct file *file, const char __user *buf, size_t size, loff_t *offset)
{
struct i2c_msg msg[1];
u8 val[2];
int ret; if(size!=2) //地址 数据
return -EINVAL; copy_from_user(val,buf,2); //获取 地址 数据
msg[0].addr=at24c02_client->addr;
msg[0].flags=0; //写标志
msg[0].len =2;
msg[0].buf =val; //写入要写的地址 数据 ret=i2c_transfer(at24c02_client->adapter, msg, 1);
if(ret==1) //表示1个msg传输成功
{
return 0;
}
else
return -EAGAIN;
}static struct file_operations at24c02_fops={
.owner = THIS_MODULE,
.read = at24c02_read,
.write = at24c02_write,
};/*2.定义i2c_client_address_data结构体,保存24C02的设备地址*/
static unsigned short ignore[] = { I2C_CLIENT_END };
static unsigned short normal_addr[] = {0X50, I2C_CLIENT_END };
static unsigned short force_addr[] = {ANY_I2C_BUS, 0x60, I2C_CLIENT_END};
static unsigned short * forces[] = {force_addr, NULL};
static struct i2c_client_address_data at24c02_addr={
.normal_i2c=normal_addr,
.probe=ignore,
.ignore=ignore,
// .forces=forces, // 强制地址
};/*3. 定义一个i2c_driver驱动结构体*/
static int at24c02_attach_adapter(struct i2c_adapter *adapter);
static int at24c02_detach_client(struct i2c_client *client);
static int at24c02_detect(struct i2c_adapter *adap, int addr, int kind);/* This is the driver that will be inserted */
static struct i2c_driver at24c02_driver = {
.driver = {
.name = "at24c02",
}, .attach_adapter = at24c02_attach_adapter, //绑定回调函数
.detach_client = at24c02_detach_client, //解绑回调函数
};/*3.1 设置i2c_driver-> attach_adapter*/
static int at24c02_attach_adapter(struct i2c_adapter *adapter)
{
return i2c_probe(adapter,&at24c02_addr, at24c02_detect);
}/*3.2 设置i2c_driver-> detach_client*/
static int at24c02_detach_client(struct i2c_client *client)
{
printk("at24c02_detach_client\n"); i2c_detach_client(at24c02_client) ;
kfree(at24c02_client);

class_device_destroy(at24c02_class,MKDEV(at24c02_major, 0));
class_destroy(at24c02_class); return 0;
}/*4.写回调函数,里面注册i2c_client,字符设备*/
static int at24c02_detect(struct i2c_adapter *adap, int addr, int kind)
{
printk("at24c02_detect\n"); /* 4.1 分配并设置i2c_client */
at24c02_client= kzalloc(sizeof(struct i2c_client), GFP_KERNEL); at24c02_client->addr = addr;
at24c02_client->adapter = adap;
at24c02_client->driver = &at24c02_driver;
at24c02_client->flags = 0;
strlcpy(at24c02_client->name, "at24c02", I2C_NAME_SIZE); /*4.2 使用i2c_attach_client()将i2c_client与适配器进行连接*/
i2c_attach_client(at24c02_client) ; /*4.3 注册字符设备*/
at24c02_major= register_chrdev(0, "at24c02", &at24c02_fops);
at24c02_class=class_create(THIS_MODULE, "at24c02");
class_device_create(at24c02_class,0, MKDEV(at24c02_major, 0),0,"at24c02");
return 0;
}/*5. 写init入口函数,exit出口函数*/
static int at24c02_init(void)
{
i2c_add_driver(&at24c02_driver);
return 0;
}
static void at24c02_exit(void)
{
i2c_del_driver(&at24c02_driver);
}
module_init(at24c02_init);
module_exit(at24c02_exit);
MODULE_LICENSE("GPL");