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研发客服s3c2440的i2c控制器驱动(精简DIY)，直接上代码，注释很详细：
#include
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//#define PRINTK printk
#define PRINTK(...)
enum s3c24xx_i2c_state {
STATE_IDLE,
STATE_START,
STATE_READ,
STATE_WRITE,
STATE_STOP
};
//i2c控制器寄存器
struct s3c2440_i2c_regs {
unsigned int iiccon;
unsigned int iicstat;
unsigned int iicadd;
unsigned int iicds;
unsigned int iiclc;
};
//i2c数据传输载体
struct s3c2440_i2c_xfer_data {
struct i2c_msg *msgs;
int msn_num;
int cur_msg;
int cur_ptr;
int state;
int err;
wait_queue_head_t wait;
};
static struct s3c2440_i2c_xfer_data s3c2440_i2c_xfer_data;
static struct s3c2440_i2c_regs *s3c2440_i2c_regs;
static void s3c2440_i2c_start(void)
{
s3c2440_i2c_xfer_data.state = STATE_START;
if (s3c2440_i2c_xfer_data.msgs->flags & I2C_M_RD) /* 读 */
{
s3c2440_i2c_regs->iicds = s3c2440_i2c_xfer_data.msgs->addr << 1;
s3c2440_i2c_regs->iicstat = 0xb0; // 主机接收，启动
}
else /* 写 */
{
s3c2440_i2c_regs->iicds = s3c2440_i2c_xfer_data.msgs->addr << 1;
s3c2440_i2c_regs->iicstat = 0xf0; // 主机发送，启动
}
}
static void s3c2440_i2c_stop(int err)
{
s3c2440_i2c_xfer_data.state = STATE_STOP;
s3c2440_i2c_xfer_data.err = err;
PRINTK("STATE_STOP, err = %dn", err);
if (s3c2440_i2c_xfer_data.msgs->flags & I2C_M_RD) /* 读 */
{
// 下面两行恢复I2C操作，发出P信号
s3c2440_i2c_regs->iicstat = 0x90;
s3c2440_i2c_regs->iiccon = 0xaf;
ndelay(50); // 等待一段时间以便P信号已经发出
}
else /* 写 */
{
// 下面两行用来恢复I2C操作，发出P信号
s3c2440_i2c_regs->iicstat = 0xd0;
s3c2440_i2c_regs->iiccon = 0xaf;
ndelay(50); // 等待一段时间以便P信号已经发出
}
/* 唤醒 */
wake_up(&s3c2440_i2c_xfer_data.wait);
}
//i2c总线数据传输处理函数
static int s3c2440_i2c_xfer(struct i2c_adapter *adap,
struct i2c_msg *msgs, int num)
{
unsigned long timeout;
/* 把num个msg的I2C数据发送出去/读进来 */
s3c2440_i2c_xfer_data.msgs = msgs;
s3c2440_i2c_xfer_data.msn_num = num;
s3c2440_i2c_xfer_data.cur_msg = 0;
s3c2440_i2c_xfer_data.cur_ptr = 0;
s3c2440_i2c_xfer_data.err = -ENODEV; //确认是否有ack应答
s3c2440_i2c_start(); //发出start信号，判断read or write
/* 休眠-等待i2c读写状态改变 */
timeout = wait_event_timeout(s3c2440_i2c_xfer_data.wait, (s3c2440_i2c_xfer_data.state == STATE_STOP), HZ * 5); //等待状态成立或5s
if (0 == timeout)
{
printk("s3c2440_i2c_xfer time outn");
return -ETIMEDOUT;
}
else
{
return s3c2440_i2c_xfer_data.err;
}
}
static u32 s3c2440_i2c_func(struct i2c_adapter *adap)
{
return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_PROTOCOL_MANGLING;
}
static const struct i2c_algorithm s3c2440_i2c_algo = {
// .smbus_xfer = , //smbus是i2c传输的一个子集,支持的话可以在这里指定处理函数
.master_xfer = s3c2440_i2c_xfer, //传输函数
.functionality = s3c2440_i2c_func,
};
/* 1. 分配/设置i2c_adapter
*/
static struct i2c_adapter s3c2440_i2c_adapter = {
.name = "s3c2440_sheldon",
.algo = &s3c2440_i2c_algo, //算法函数
.owner = THIS_MODULE,
};
static int isLastMsg(void)
{
return (s3c2440_i2c_xfer_data.cur_msg == s3c2440_i2c_xfer_data.msn_num - 1);
}
static int isEndData(void)
{
return (s3c2440_i2c_xfer_data.cur_ptr >= s3c2440_i2c_xfer_data.msgs->len);
}
static int isLastData(void)
{
return (s3c2440_i2c_xfer_data.cur_ptr == s3c2440_i2c_xfer_data.msgs->len - 1);
}
static irqreturn_t s3c2440_i2c_xfer_irq(int irq, void *dev_id)
{
unsigned int iicSt;
iicSt = s3c2440_i2c_regs->iicstat; //读取i2c控制器的状态寄存器，判断是否读写成功
if(iicSt & 0x8){ printk("Bus arbitration failednr"); }
switch (s3c2440_i2c_xfer_data.state)
{
case STATE_START : /* 发出S和设备地址后,产生中断 */
{
PRINTK("Startn");
/* 如果没有ACK, 返回错误 */
if (iicSt & S3C2410_IICSTAT_LASTBIT)
{
s3c2440_i2c_stop(-ENODEV);
break;
}
if (isLastMsg() && isEndData())
{
s3c2440_i2c_stop(0);
break;
}
/* 进入下一个状态 */
if (s3c2440_i2c_xfer_data.msgs->flags & I2C_M_RD) /* 读 */
{
s3c2440_i2c_xfer_data.state = STATE_READ;
goto next_read;
}
else
{
s3c2440_i2c_xfer_data.state = STATE_WRITE;
}
}
case STATE_WRITE:
{
PRINTK("STATE_WRITEn");
/* 如果没有ACK, 返回错误 */
if (iicSt & S3C2410_IICSTAT_LASTBIT)
{
s3c2440_i2c_stop(-ENODEV);
break;
}
if (!isEndData()) /* 如果当前msg还有数据要发送 */
{
s3c2440_i2c_regs->iicds = s3c2440_i2c_xfer_data.msgs->buf[s3c2440_i2c_xfer_data.cur_ptr];
s3c2440_i2c_xfer_data.cur_ptr++;
// 将数据写入IICDS后，需要一段时间才能出现在SDA线上
ndelay(50);
s3c2440_i2c_regs->iiccon = 0xaf; // 恢复I2C传输
break;
}
else if (!isLastMsg())
{
/* 开始处理下一个消息 */
s3c2440_i2c_xfer_data.msgs++;
s3c2440_i2c_xfer_data.cur_msg++;
s3c2440_i2c_xfer_data.cur_ptr = 0;
s3c2440_i2c_xfer_data.state = STATE_START;
/* 发出START信号和发出设备地址 */
s3c2440_i2c_start();
break;
}
else
{
/* 是最后一个消息的最后一个数据 */
s3c2440_i2c_stop(0);
break;
}
break;
}
case STATE_READ:
{
PRINTK("STATE_READn");
/* 读出数据 */
s3c2440_i2c_xfer_data.msgs->buf[s3c2440_i2c_xfer_data.cur_ptr] = s3c2440_i2c_regs->iicds;
s3c2440_i2c_xfer_data.cur_ptr++;
next_read:
if (!isEndData()) /* 如果数据没读写, 继续发起读操作 */
{
if (isLastData()) /* 如果即将读的数据是最后一个, 不发ack */
{
s3c2440_i2c_regs->iiccon = 0x2f; // 恢复I2C传输，接收到下一数据时无ACK
}
else
{
s3c2440_i2c_regs->iiccon = 0xaf; // 恢复I2C传输，接收到下一数据时发出ACK
}
break;
}
else if (!isLastMsg())
{
/* 开始处理下一个消息 */
s3c2440_i2c_xfer_data.msgs++;
s3c2440_i2c_xfer_data.cur_msg++;
s3c2440_i2c_xfer_data.cur_ptr = 0;
s3c2440_i2c_xfer_data.state = STATE_START;
/* 发出START信号和发出设备地址 */
s3c2440_i2c_start();
break;
}
else
{
/* 是最后一个消息的最后一个数据 */
s3c2440_i2c_stop(0);
break;
}
break;
}