s3c2410_i2c总线驱动及at24c02设备驱动实例

 

/* linux/drivers/i2c/busses/i2c-s3c2410.c
 *
 * Copyright (C) 2004,2005 Simtec Electronics
 * Ben Dooks <[e-mail]>
 *
 * S3C2410 I2C Controller
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/i2c.h>
#include <linux/i2c-id.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/platform_device.h>
#include <linux/clk.h>

#include <asm/hardware.h>
#include <asm/irq.h>
#include <asm/io.h>

#include <asm/arch/regs-gpio.h>
#include <asm/arch/regs-iic.h>
#include <asm/arch/iic.h>

/* i2c controller state */

enum s3c24xx_i2c_state {
 STATE_IDLE,
 STATE_START,
 STATE_READ,
 STATE_WRITE,
 STATE_STOP
};

struct s3c24xx_i2c {  //i2c结构体
 spinlock_t  lock;
 wait_queue_head_t wait;

 struct i2c_msg  *msg;
 unsigned int  msg_num;
 unsigned int  msg_idx;
 unsigned int  msg_ptr;

 unsigned int  tx_setup;

 enum s3c24xx_i2c_state state;

 void __iomem  *regs;
 struct clk  *clk;
 struct device  *dev;
 struct resource  *irq;
 struct resource  *ioarea;
 struct i2c_adapter adap;
};

/* default platform data to use if not supplied in the platform_device
*/

static struct s3c2410_platform_i2c s3c24xx_i2c_default_platform = {
 .flags  = 0,
 .slave_addr = 0x10,
 .bus_freq = 100*1000,
 .max_freq = 400*1000,
 .sda_delay = S3C2410_IICLC_SDA_DELAY5 | S3C2410_IICLC_FILTER_ON,
};

/* s3c24xx_i2c_is2440()
 *
 * return true is this is an s3c2440
*/

static inline int s3c24xx_i2c_is2440(struct s3c24xx_i2c *i2c)
{
 struct platform_device *pdev = to_platform_device(i2c->dev);

 return !strcmp(pdev->name, "s3c2440-i2c");
}

/* s3c24xx_i2c_get_platformdata
 *
 * get the platform data associated with the given device, or return
 * the default if there is none
*/

static inline struct s3c2410_platform_i2c *s3c24xx_i2c_get_platformdata(struct device *dev)
{
 if (dev->platform_data != NULL)
  return (struct s3c2410_platform_i2c *)dev->platform_data;

 return &s3c24xx_i2c_default_platform;
}

/* s3c24xx_i2c_master_complete
 *
 * complete the message and wake up the caller, using the given return code,
 * or zero to mean ok.
*/

static inline void s3c24xx_i2c_master_complete(struct s3c24xx_i2c *i2c, int ret)
{
 dev_dbg(i2c->dev, "master_complete %d\n", ret);

 i2c->msg_ptr = 0;
 i2c->msg = NULL;
 i2c->msg_idx ++;
 i2c->msg_num = 0;
 if (ret)
  i2c->msg_idx = ret;

 wake_up(&i2c->wait);
}

static inline void s3c24xx_i2c_disable_ack(struct s3c24xx_i2c *i2c)
{
 unsigned long tmp;
 
 tmp = readl(i2c->regs + S3C2410_IICCON);
 writel(tmp & ~S3C2410_IICCON_ACKEN, i2c->regs + S3C2410_IICCON);

}

static inline void s3c24xx_i2c_enable_ack(struct s3c24xx_i2c *i2c)
{
 unsigned long tmp;
 
 tmp = readl(i2c->regs + S3C2410_IICCON);
 writel(tmp | S3C2410_IICCON_ACKEN, i2c->regs + S3C2410_IICCON);

}

/* irq enable/disable functions */

static inline void s3c24xx_i2c_disable_irq(struct s3c24xx_i2c *i2c)
{
 unsigned long tmp;
 
 tmp = readl(i2c->regs + S3C2410_IICCON);
 writel(tmp & ~S3C2410_IICCON_IRQEN, i2c->regs + S3C2410_IICCON);
}

static inline void s3c24xx_i2c_enable_irq(struct s3c24xx_i2c *i2c)
{
 unsigned long tmp;
 
 tmp = readl(i2c->regs + S3C2410_IICCON);
 writel(tmp | S3C2410_IICCON_IRQEN, i2c->regs + S3C2410_IICCON);
}

/* s3c24xx_i2c_message_start
 *
 * put the start of a message onto the bus
*/

static void s3c24xx_i2c_message_start(struct s3c24xx_i2c *i2c,
          struct i2c_msg *msg)
{
 unsigned int addr = (msg->addr & 0x7f) << 1;
 unsigned long stat;
 unsigned long iiccon;
//写对应的适配器控制器
 stat = 0;
 stat |=  S3C2410_IICSTAT_TXRXEN;

 if (msg->flags & I2C_M_RD) {
  stat |= S3C2410_IICSTAT_MASTER_RX;
  addr |= 1;
 } else
  stat |= S3C2410_IICSTAT_MASTER_TX;

 if (msg->flags & I2C_M_REV_DIR_ADDR)
  addr ^= 1;

 // todo - check for wether ack wanted or not
 s3c24xx_i2c_enable_ack(i2c);//使能应答
//向i2c从设备传递开始位和从设备地址
 iiccon = readl(i2c->regs + S3C2410_IICCON);
 writel(stat, i2c->regs + S3C2410_IICSTAT);
 
 dev_dbg(i2c->dev, "START: %08lx to IICSTAT, %02x to DS\n", stat, addr);
 writeb(addr, i2c->regs + S3C2410_IICDS);
 
 /* delay here to ensure the data byte has gotten onto the bus
  * before the transaction is started */

 ndelay(i2c->tx_setup);

 dev_dbg(i2c->dev, "iiccon, %08lx\n", iiccon);
 writel(iiccon, i2c->regs + S3C2410_IICCON);
 
 stat |=  S3C2410_IICSTAT_START;
 writel(stat, i2c->regs + S3C2410_IICSTAT);
}

static inline void s3c24xx_i2c_stop(struct s3c24xx_i2c *i2c, int ret)
{
 unsigned long iicstat = readl(i2c->regs + S3C2410_IICSTAT);

 dev_dbg(i2c->dev, "STOP\n");

 /* stop the transfer */
 iicstat &= ~ S3C2410_IICSTAT_START;
 writel(iicstat, i2c->regs + S3C2410_IICSTAT);
 
 i2c->state = STATE_STOP;
 
 s3c24xx_i2c_master_complete(i2c, ret);
 s3c24xx_i2c_disable_irq(i2c);
}

/* helper functions to determine the current state in the set of
 * messages we are sending */

/* is_lastmsg()
 *
 * returns TRUE if the current message is the last in the set
*/

static inline int is_lastmsg(struct s3c24xx_i2c *i2c)
{
 return i2c->msg_idx >= (i2c->msg_num - 1);
}

/* is_msglast
 *
 * returns TRUE if we this is the last byte in the current message
*/

static inline int is_msglast(struct s3c24xx_i2c *i2c)
{
 return i2c->msg_ptr == i2c->msg->len-1;
}

/* is_msgend
 *
 * returns TRUE if we reached the end of the current message
*/

static inline int is_msgend(struct s3c24xx_i2c *i2c)
{
 return i2c->msg_ptr >= i2c->msg->len;
}

/* i2s_s3c_irq_nextbyte
 *
 * process an interrupt and work out what to do
 把传输工作进一步推进
 */

static int i2s_s3c_irq_nextbyte(struct s3c24xx_i2c *i2c, unsigned long iicstat)
{
 unsigned long tmp;
 unsigned char byte;
 int ret = 0;

 switch (i2c->state) {

 case STATE_IDLE:
  dev_err(i2c->dev, "%s: called in STATE_IDLE\n", __FUNCTION__);
  goto out;
  break;

 case STATE_STOP:
  dev_err(i2c->dev, "%s: called in STATE_STOP\n", __FUNCTION__);
  s3c24xx_i2c_disable_irq(i2c);  
  goto out_ack;

 case STATE_START:
  /* last thing we did was send a start condition on the
   * bus, or started a new i2c message
   我们最近做的一件事是启动一个新的i2c消息
   */
  
  if (iicstat  & S3C2410_IICSTAT_LASTBIT &&
      !(i2c->msg->flags & I2C_M_IGNORE_NAK)) {
   /* ack was not received... 没有收到ACK*/

   dev_dbg(i2c->dev, "ack was not received\n");
   s3c24xx_i2c_stop(i2c, -EREMOTEIO);
   goto out_ack;
  }

  if (i2c->msg->flags & I2C_M_RD)
   i2c->state = STATE_READ;
  else
   i2c->state = STATE_WRITE;

  /* terminate the transfer if there is nothing to do
   * (used by the i2c probe to find devices */

  if (is_lastmsg(i2c) && i2c->msg->len == 0) {
   s3c24xx_i2c_stop(i2c, 0);
   goto out_ack;
  }

  if (i2c->state == STATE_READ)
   goto prepare_read;

  /* fall through to the write state, as we will need to
   * send a byte as well 进入写状态*/

 case STATE_WRITE:
  /* we are writing data to the device... check for the
   * end of the message, and if so, work out what to do
   */

 retry_write:
  if (!is_msgend(i2c)) {
   byte = i2c->msg->buf[i2c->msg_ptr++];
   writeb(byte, i2c->regs + S3C2410_IICDS);

   /* delay after writing the byte to allow the
    * data setup time on the bus, as writing the
    * data to the register causes the first bit
    * to appear on SDA, and SCL will change as
    * soon as the interrupt is acknowledged */

   ndelay(i2c->tx_setup);

  } else if (!is_lastmsg(i2c)) {
   /* we need to go to the next i2c message 推进到下一条消息*/

   dev_dbg(i2c->dev, "WRITE: Next Message\n");

   i2c->msg_ptr = 0;
   i2c->msg_idx ++;
   i2c->msg++;
   
   /* check to see if we need to do another message 检查是否要为该消息产生开始位*/
   if (i2c->msg->flags & I2C_M_NOSTART) {

    if (i2c->msg->flags & I2C_M_RD) {
     /* cannot do this, the controller
      * forces us to send a new START
      * when we change direction */

     s3c24xx_i2c_stop(i2c, -EINVAL);
    }

    goto retry_write;
   } else {
   
    /* send the new start 发送新的开始位*/
    s3c24xx_i2c_message_start(i2c, i2c->msg);
    i2c->state = STATE_START;
   }

  } else {
   /* send stop */

   s3c24xx_i2c_stop(i2c, 0);
  }
  break;

 case STATE_READ:
  /* we have a byte of data in the data register, do
   * something with it, and then work out wether we are
   * going to do any more read/write
   */

  if (!(i2c->msg->flags & I2C_M_IGNORE_NAK) &&
      !(is_msglast(i2c) && is_lastmsg(i2c))) {

   if (iicstat & S3C2410_IICSTAT_LASTBIT) {
    dev_dbg(i2c->dev, "READ: No Ack\n");

    s3c24xx_i2c_stop(i2c, -ECONNREFUSED);
    goto out_ack;
   }
  }

  byte = readb(i2c->regs + S3C2410_IICDS);
  i2c->msg->buf[i2c->msg_ptr++] = byte;

 prepare_read:
  if (is_msglast(i2c)) {
   /* last byte of buffer */

   if (is_lastmsg(i2c))
    s3c24xx_i2c_disable_ack(i2c);
   
  } else if (is_msgend(i2c)) {
   /* ok, we've read the entire buffer, see if there
    * is anything else we need to do */

   if (is_lastmsg(i2c)) {
    /* last message, send stop and complete */
    dev_dbg(i2c->dev, "READ: Send Stop\n");

    s3c24xx_i2c_stop(i2c, 0);
   } else {
    /* go to the next transfer */
    dev_dbg(i2c->dev, "READ: Next Transfer\n");

    i2c->msg_ptr = 0;
    i2c->msg_idx++;
    i2c->msg++;
   }
  }

  break;
 }

 /* acknowlegde the IRQ and get back on with the work */

 out_ack:
 tmp = readl(i2c->regs + S3C2410_IICCON); 
 tmp &= ~S3C2410_IICCON_IRQPEND;
 writel(tmp, i2c->regs + S3C2410_IICCON);
 out:
 return ret;
}

/* s3c24xx_i2c_irq
 *
 * top level IRQ servicing routine
*/

static irqreturn_t s3c24xx_i2c_irq(int irqno, void *dev_id)//适配器中断处理函数
{
 struct s3c24xx_i2c *i2c = dev_id;
 unsigned long status;
 unsigned long tmp;

 status = readl(i2c->regs + S3C2410_IICSTAT);

 if (status & S3C2410_IICSTAT_ARBITR) {
  // deal with arbitration loss
  dev_err(i2c->dev, "deal with arbitration loss\n");
 }

 if (i2c->state == STATE_IDLE) {
  dev_dbg(i2c->dev, "IRQ: error i2c->state == IDLE\n");

  tmp = readl(i2c->regs + S3C2410_IICCON); 
  tmp &= ~S3C2410_IICCON_IRQPEND;
  writel(tmp, i2c->regs +  S3C2410_IICCON);
  goto out;
 }
 
 /* pretty much this leaves us with the fact that we've
  * transmitted or received whatever byte we last sent */

 i2s_s3c_irq_nextbyte(i2c, status);//把传输工作进一步推进

 out:
 return IRQ_HANDLED;
}

/* s3c24xx_i2c_set_master
 *
 * get the i2c bus for a master transaction
*/

static int s3c24xx_i2c_set_master(struct s3c24xx_i2c *i2c)
{
 unsigned long iicstat;
 int timeout = 400;

 while (timeout-- > 0) {
  iicstat = readl(i2c->regs + S3C2410_IICSTAT);
  
  if (!(iicstat & S3C2410_IICSTAT_BUSBUSY))
   return 0;

  msleep(1);
 }

 dev_dbg(i2c->dev, "timeout: GPEDAT is %08x\n",
  __raw_readl(S3C2410_GPEDAT));

 return -ETIMEDOUT;
}

/* s3c24xx_i2c_doxfer
 *
 * this starts an i2c transfer
*/

static int s3c24xx_i2c_doxfer(struct s3c24xx_i2c *i2c, struct i2c_msg *msgs, int num)
{
 unsigned long timeout;
 int ret;

 ret = s3c24xx_i2c_set_master(i2c);//设置为i2c主设备
 if (ret != 0) {
  dev_err(i2c->dev, "cannot get bus (error %d)\n", ret);
  ret = -EAGAIN;
  goto out;
 }

 spin_lock_irq(&i2c->lock);
//初始化s3c24xx_i2c 结构体
 i2c->msg     = msgs;
 i2c->msg_num = num;
 i2c->msg_ptr = 0;
 i2c->msg_idx = 0;
 i2c->state   = STATE_START;

 s3c24xx_i2c_enable_irq(i2c);//中断使能
 s3c24xx_i2c_message_start(i2c, msgs);//启动i2c消息传输
 spin_unlock_irq(&i2c->lock);
 
 timeout = wait_event_timeout(i2c->wait, i2c->msg_num == 0, HZ * 5);

 ret = i2c->msg_idx;

 /* having these next two as dev_err() makes life very
  * noisy when doing an i2cdetect */

 if (timeout == 0)
  dev_dbg(i2c->dev, "timeout\n");
 else if (ret != num)
  dev_dbg(i2c->dev, "incomplete xfer (%d)\n", ret);

 /* ensure the stop has been through the bus */

 msleep(1);

 out:
 return ret;
}

/* s3c24xx_i2c_xfer
 *
 * first port of call from the i2c bus code when an message needs
 * transferring across the i2c bus.
*/
//.master_xfer  = s3c24xx_i2c_xfer,
static int s3c24xx_i2c_xfer(struct i2c_adapter *adap,
   struct i2c_msg *msgs, int num)
{
 struct s3c24xx_i2c *i2c = (struct s3c24xx_i2c *)adap->algo_data;
 int retry;
 int ret;

 for (retry = 0; retry < adap->retries; retry++) {

  ret = s3c24xx_i2c_doxfer(i2c, msgs, num);//传输i2c消息

  if (ret != -EAGAIN)
   return ret;

  dev_dbg(i2c->dev, "Retrying transmission (%d)\n", retry);

  udelay(100);
 }

 return -EREMOTEIO;
}

/* declare our i2c functionality */
static u32 s3c24xx_i2c_func(struct i2c_adapter *adap)
{
 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_PROTOCOL_MANGLING;
}

/* i2c bus registration info */

static const struct i2c_algorithm s3c24xx_i2c_algorithm = {
 .master_xfer  = s3c24xx_i2c_xfer,
 .functionality  = s3c24xx_i2c_func,
};

static struct s3c24xx_i2c s3c24xx_i2c = {//结构体
 .lock  = __SPIN_LOCK_UNLOCKED(s3c24xx_i2c.lock),
 .wait  = __WAIT_QUEUE_HEAD_INITIALIZER(s3c24xx_i2c.wait),
 .tx_setup = 50,
 .adap  = {
  .name   = "s3c2410-i2c",
  .owner   = THIS_MODULE,
  .algo   = &s3c24xx_i2c_algorithm,
  .retries  = 2,
  .class   = I2C_CLASS_HWMON,
 },
};

/* s3c24xx_i2c_calcdivisor
 *
 * return the divisor settings for a given frequency
*/

static int s3c24xx_i2c_calcdivisor(unsigned long clkin, unsigned int wanted,
       unsigned int *div1, unsigned int *divs)
{
 unsigned int calc_divs = clkin / wanted;
 unsigned int calc_div1;

 if (calc_divs > (16*16))
  calc_div1 = 512;
 else
  calc_div1 = 16;

 calc_divs += calc_div1-1;
 calc_divs /= calc_div1;

 if (calc_divs == 0)
  calc_divs = 1;
 if (calc_divs > 17)
  calc_divs = 17;

 *divs = calc_divs;
 *div1 = calc_div1;

 return clkin / (calc_divs * calc_div1);
}

/* freq_acceptable
 *
 * test wether a frequency is within the acceptable range of error
*/

static inline int freq_acceptable(unsigned int freq, unsigned int wanted)
{
 int diff = freq - wanted;

 return (diff >= -2 && diff <= 2);
}

/* s3c24xx_i2c_getdivisor
 *
 * work out a divisor for the user requested frequency setting,
 * either by the requested frequency, or scanning the acceptable
 * range of frequencies until something is found
*/

static int s3c24xx_i2c_getdivisor(struct s3c24xx_i2c *i2c,
      struct s3c2410_platform_i2c *pdata,
      unsigned long *iicon,
      unsigned int *got)
{
 unsigned long clkin = clk_get_rate(i2c->clk);
 
 unsigned int divs, div1;
 int freq;
 int start, end;

 clkin /= 1000;  /* clkin now in KHz */
    
 dev_dbg(i2c->dev,  "pdata %p, freq %lu %lu..%lu\n",
   pdata, pdata->bus_freq, pdata->min_freq, pdata->max_freq);

 if (pdata->bus_freq != 0) {
  freq = s3c24xx_i2c_calcdivisor(clkin, pdata->bus_freq/1000,
            &div1, &divs);
  if (freq_acceptable(freq, pdata->bus_freq/1000))
   goto found;
 }

 /* ok, we may have to search for something suitable... */

 start = (pdata->max_freq == 0) ? pdata->bus_freq : pdata->max_freq;
 end = pdata->min_freq;

 start /= 1000;
 end /= 1000;

 /* search loop... */

 for (; start > end; start--) {
  freq = s3c24xx_i2c_calcdivisor(clkin, start, &div1, &divs);
  if (freq_acceptable(freq, start))
   goto found;
 }

 /* cannot find frequency spec */

 return -EINVAL;

 found:
 *got = freq;
 *iicon |= (divs-1);
 *iicon |= (div1 == 512) ? S3C2410_IICCON_TXDIV_512 : 0;
 return 0;
}

/* s3c24xx_i2c_init
 *
 * initialise the controller, set the IO lines and frequency
*/

static int s3c24xx_i2c_init(struct s3c24xx_i2c *i2c)
{
 unsigned long iicon = S3C2410_IICCON_IRQEN | S3C2410_IICCON_ACKEN;
 struct s3c2410_platform_i2c *pdata;
 unsigned int freq;

 /* get the plafrom data */

 pdata = s3c24xx_i2c_get_platformdata(i2c->adap.dev.parent);

 /* inititalise the gpio */

 s3c2410_gpio_cfgpin(S3C2410_GPE15, S3C2410_GPE15_IICSDA);
 s3c2410_gpio_cfgpin(S3C2410_GPE14, S3C2410_GPE14_IICSCL);

 /* write slave address */
 
 writeb(pdata->slave_addr, i2c->regs + S3C2410_IICADD);

 dev_info(i2c->dev, "slave address 0x%02x\n", pdata->slave_addr);

 /* we need to work out the divisors for the clock... */

 if (s3c24xx_i2c_getdivisor(i2c, pdata, &iicon, &freq) != 0) {
  dev_err(i2c->dev, "cannot meet bus frequency required\n");
  return -EINVAL;
 }

 /* todo - check that the i2c lines aren't being dragged anywhere */

 dev_info(i2c->dev, "bus frequency set to %d KHz\n", freq);
 dev_dbg(i2c->dev, "S3C2410_IICCON=0x%02lx\n", iicon);
 
 writel(iicon, i2c->regs + S3C2410_IICCON);

 /* check for s3c2440 i2c controller  */

 if (s3c24xx_i2c_is2440(i2c)) {
  dev_dbg(i2c->dev, "S3C2440_IICLC=%08x\n", pdata->sda_delay);

  writel(pdata->sda_delay, i2c->regs + S3C2440_IICLC);
 }

 return 0;
}

/* s3c24xx_i2c_probe
 *初始化适配器硬件
 * called by the bus driver when a suitable device is found
*/

static int s3c24xx_i2c_probe(struct platform_device *pdev)
{  
 struct s3c24xx_i2c *i2c = &s3c24xx_i2c;
 struct resource *res;
 int ret;

 /* find the clock and enable it 发现时钟并使能它*/

 i2c->dev = &pdev->dev;
 i2c->clk = clk_get(&pdev->dev, "i2c");
 if (IS_ERR(i2c->clk)) {
  dev_err(&pdev->dev, "cannot get clock\n");
  ret = -ENOENT;
  goto err_noclk;
 }

 dev_dbg(&pdev->dev, "clock source %p\n", i2c->clk);

 clk_enable(i2c->clk);

 /* map the registers 映射寄存器*/
     //申请i2c适配器使用的i/o地址
 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 if (res == NULL) {
  dev_err(&pdev->dev, "cannot find IO resource\n");
  ret = -ENOENT;
  goto err_clk;
 }
       //请求内存区域
 i2c->ioarea = request_mem_region(res->start, (res->end-res->start)+1,
      pdev->name);

 if (i2c->ioarea == NULL) {
  dev_err(&pdev->dev, "cannot request IO\n");//控制输出信息
  ret = -ENXIO;
  goto err_clk;
 }
//物理地址到虚拟地址的映射
 i2c->regs = ioremap(res->start, (res->end-res->start)+1);

 if (i2c->regs == NULL) {
  dev_err(&pdev->dev, "cannot map IO\n");
  ret = -ENXIO;
  goto err_ioarea;
 }

 dev_dbg(&pdev->dev, "registers %p (%p, %p)\n", i2c->regs, i2c->ioarea, res);

 /* setup info block for the i2c core 设置i2c核心需要的信息*/

 i2c->adap.algo_data = i2c;
 i2c->adap.dev.parent = &pdev->dev;

 /* initialise the i2c controller */

 ret = s3c24xx_i2c_init(i2c);
 if (ret != 0)
  goto err_iomap;

 /* find the IRQ for this unit (note, this relies on the init call to
  * ensure no current IRQs pending
  */

 res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 if (res == NULL) {
  dev_err(&pdev->dev, "cannot find IRQ\n");
  ret = -ENOENT;
  goto err_iomap;
 }
//申请中断
 ret = request_irq(res->start, s3c24xx_i2c_irq, IRQF_DISABLED,
     pdev->name, i2c);

 if (ret != 0) {
  dev_err(&pdev->dev, "cannot claim IRQ\n");
  goto err_iomap;
 }

 i2c->irq = res;
  
 dev_dbg(&pdev->dev, "irq resource %p (%lu)\n", res,
  (unsigned long)res->start);

 ret = i2c_add_adapter(&i2c->adap);//增加i2c_adapter适配器
 if (ret < 0) {
  dev_err(&pdev->dev, "failed to add bus to i2c core\n");
  goto err_irq;
 }

 platform_set_drvdata(pdev, i2c);

 dev_info(&pdev->dev, "%s: S3C I2C adapter\n", i2c->adap.dev.bus_id);
 return 0;

 err_irq:
 free_irq(i2c->irq->start, i2c);

 err_iomap:
 iounmap(i2c->regs);

 err_ioarea:
 release_resource(i2c->ioarea);
 kfree(i2c->ioarea);

 err_clk:
 clk_disable(i2c->clk);
 clk_put(i2c->clk);

 err_noclk:
 return ret;
}

/* s3c24xx_i2c_remove
 *
 * called when device is removed from the bus
*/

static int s3c24xx_i2c_remove(struct platform_device *pdev)
{
 struct s3c24xx_i2c *i2c = platform_get_drvdata(pdev);

 i2c_del_adapter(&i2c->adap);
 free_irq(i2c->irq->start, i2c);

 clk_disable(i2c->clk);
 clk_put(i2c->clk);

 iounmap(i2c->regs);

 release_resource(i2c->ioarea);
 kfree(i2c->ioarea);

 return 0;
}

#ifdef CONFIG_PM
static int s3c24xx_i2c_resume(struct platform_device *dev)
{
 struct s3c24xx_i2c *i2c = platform_get_drvdata(dev);

 if (i2c != NULL)
  s3c24xx_i2c_init(i2c);

 return 0;
}

#else
#define s3c24xx_i2c_resume NULL
#endif

/* device driver for platform bus bits */

static struct platform_driver s3c2410_i2c_driver = {
 .probe  = s3c24xx_i2c_probe,
 .remove  = s3c24xx_i2c_remove,
 .resume  = s3c24xx_i2c_resume,
 .driver  = {
  .owner = THIS_MODULE,
  .name = "s3c2410-i2c",
 },
};

static struct platform_driver s3c2440_i2c_driver = {//platform_driver结构体
 .probe  = s3c24xx_i2c_probe,
 .remove  = s3c24xx_i2c_remove,
 .resume  = s3c24xx_i2c_resume,
 .driver  = {
  .owner = THIS_MODULE,
  .name = "s3c2440-i2c",
 },
};

static int __init i2c_adap_s3c_init(void)
{
 int ret;

 ret = platform_driver_register(&s3c2410_i2c_driver);//注册
 if (ret == 0) {
  ret = platform_driver_register(&s3c2440_i2c_driver);
  if (ret)
   platform_driver_unregister(&s3c2410_i2c_driver);
 }

 return ret;
}

static void __exit i2c_adap_s3c_exit(void)
{
 platform_driver_unregister(&s3c2410_i2c_driver);
 platform_driver_unregister(&s3c2440_i2c_driver);
}

module_init(i2c_adap_s3c_init);
module_exit(i2c_adap_s3c_exit);

MODULE_DESCRIPTION("S3C24XX I2C Bus driver");
MODULE_AUTHOR("Ben Dooks, <[e-mail]>");
MODULE_LICENSE("GPL");

 

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/string.h>
#include <linux/rtc.h>  /* get the user-level API */
#include <linux/bcd.h>
#include <linux/list.h>

static unsigned short ignore[] = { I2C_CLIENT_END };

/* 每个I2C设备都有一个规定的地址,看芯片手册 */
static unsigned short at24c02_addr[] = { 0x50, I2C_CLIENT_END };
static struct i2c_driver at24c02_driver;

static struct i2c_client_address_data at24c02_addr_data = {
 .normal_i2c = at24c02_addr,
 .probe      = ignore,
 .ignore     = ignore,
};

static struct i2c_client *at24c02_client;
static char name[] = "at24c02";

static int major;
static struct class *at24c02_class;
static unsigned char at24c02_buf[1024];

static int at24c02_read_byte(struct i2c_client *client, u8 reg, u8 *value)
{
 s32 tmp = i2c_smbus_read_byte_data(client, reg);

 if (tmp < 0)
  return -EIO;

 *value = tmp;

 return 0;
}

static int at24c02_write_byte(struct i2c_client *client, u8 reg, u8 value)
{
 s32 tmp = i2c_smbus_write_byte_data(client, reg, value);

 if (tmp < 0)
  return -EIO;

 return 0;
}

static int at24c02_read(struct file *filp, char __user *buff,
                                         size_t count, loff_t *offp)
{
    int ret;
 struct i2c_msg msg[2];
    char addr = 0;
   
    if (count > 1024)
    {
        return -EINVAL;
    }

    /* 先写地址 */
 msg[0].addr  = at24c02_client->addr;
 msg[0].flags = 0;       /* 0  表示写 */
 msg[0].len   = 1; /* 1个地址 */
 msg[0].buf   = &addr;

    /* 再读数据 */
 msg[1].addr  = at24c02_client->addr;
 msg[1].flags = I2C_M_RD;       /* 1: 表示读 */
 msg[1].len   = count;              /* 要读的数据个数 */
 msg[1].buf   = at24c02_buf;

 ret = i2c_transfer(at24c02_client->adapter, msg, 2);
   
 if (ret == 2)
 {
        copy_to_user(buff, at24c02_buf, count);
  return count;
 }
    else
        return -EIO;
   
}

static ssize_t at24c02_write(struct file *filp, const char __user *buff, size_t count, loff_t *offp)
{
    int ret;
 struct i2c_msg msg[1];
   
    if (count > 1024)
    {
        return -EINVAL;
    }

    copy_from_user(&at24c02_buf[1], buff, count);

    at24c02_buf[0] = 0; /* 表示写到哪里 */

 msg[0].addr  = at24c02_client->addr;
 msg[0].flags = 0;       /* 0  表示写 */
 msg[0].len   = count + 1; /* 1个地址+count个数据 */
 msg[0].buf   = at24c02_buf;

 ret = i2c_transfer(at24c02_client->adapter, msg, 1);
   
 if (ret == 1)
  return count;
    else
        return -EIO;
}

static struct file_operations at24c02_fops = {
    .owner   =   THIS_MODULE,    /* 这是一个宏，指向编译模块时自动创建的__this_module变量 */
    .read    =   at24c02_read,
    .write   =   at24c02_write,
};

static int at24c02_detect(struct i2c_adapter *adap, int addr, int kind)
{
    int rc;
    u8 value;

    printk("at24c02_detect\n");

   
    /* 分配一个i2c_client结构体 */
 at24c02_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
 if (!at24c02_client)
  return -ENOMEM;

 strncpy(at24c02_client->name, name, strlen(name)+1);
   
 at24c02_client->addr = addr;    /* 0x50 */
 at24c02_client->adapter = adap;
 at24c02_client->driver = &at24c02_driver;
   
#if 0   
    /* 发出I2C信号, 进一步确定at24c02是否存在 */

    rc = at24c02_read_byte(at24c02_client, 0, &value);
    if (0 != rc)
    {
        printk("AT24C02 not exist\n");
  kfree(at24c02_client);
  return -ENODEV;       
    }

    printk("Detect AT24C02\n");
#endif
    /* 注册i2c_client */
 if ((rc = i2c_attach_client(at24c02_client)) != 0) {
  kfree(at24c02_client);
  return rc;
 }

    /* register_chrdev,.. */
    major = register_chrdev(0, "at24c02", &at24c02_fops);
   
 // 构造供udev/mdev创建设备节点用的信息
 at24c02_class = class_create(THIS_MODULE, "at24c02");
 if (IS_ERR(at24c02_class))
 {
  unregister_chrdev(major, "buttons");
  return -1;
 }
 class_device_create(at24c02_class, NULL, MKDEV(major, 0), NULL, "at24c02"); 
   
    return 0;   
}

/* 识别/枚举 I2C设备 */
static int at24c02_attach_adapter(struct i2c_adapter *adapter)
{
    /* i2c_probe首先会确定是否存在地址为0x50的设备
     * 如果存在, 则使用at24c02_detect进一步处理
     */
 return i2c_probe(adapter, &at24c02_addr_data, at24c02_detect);
}

static int at24c02_detach_client(struct i2c_client *client)
{
    int err;
   
 if ((err = i2c_detach_client(at24c02_client)))
  return err;
   
    kfree(at24c02_client);

    unregister_chrdev(major, "at24c02");
 class_device_destroy(at24c02_class, MKDEV(major, 0));
 class_destroy(at24c02_class); 
   
 return 0;
}

/* 1. 构造i2c_driver */
static struct i2c_driver at24c02_driver = {
 .driver = {
  .name = "at24c02",
 },
 .attach_adapter = at24c02_attach_adapter,
 .detach_client = at24c02_detach_client,
};

int at24c02_init(void)
{
    i2c_add_driver(&at24c02_driver);
    return 0;
}

void at24c02_exit(void)
{
    i2c_del_driver(&at24c02_driver);
}

module_init(at24c02_init);
module_exit(at24c02_exit);

MODULE_LICENSE("GPL");

 测试程序：

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

/* at24c02_test r
 * at24c02_test w val
 */

void print_usage(char *str)
{
    printf("%s r     : read at24c02 addresss 0\n", str);
    printf("%s w val : write at24c02 addresss 0\n", str);
}

int main(int argc, char **argv)
{
    int fd;
    int ret;
    unsigned char buf[100];
   
    if (argc < 2)
    {
        print_usage(argv[0]);
        return -1;
    }

    fd = open("/dev/at24c02", O_RDWR);
    if (fd < 0)
    {
        printf("can't open /dev/at24c02\n");
        return -1;
    }

    if (strcmp(argv[1], "r") == 0)
    {
        ret = read(fd, buf, 100);  
        if (ret == 100)
        {
            printf("get data: %s\n", buf);
            return 0;
        }
        else
        {
            printf("can't get data\n");
            return -1;
        }
    }
    else if ((strcmp(argv[1], "w") == 0) && (argc == 3))
    {
        ret = write(fd, argv[2], strlen(argv[2]) + 1);
        if (ret >= 0)
        {
            printf("write data ok!\n");
            return 0;
        }
        else
        {
            printf("can't write\n");
            return -1;
        }
    }

    return 0;
   
}

 

 

1. at24c02_1.c
   加载后，会打印：Detect AT24C02
   修改at24c02_addr里的0x50为0x60，at24c02_detect不会被调用, 这表明：

    /* i2c_probe首先会确定是否存在地址为0x50的设备
     * 如果存在, 则使用at24c02_detect进一步处理
     */
    return i2c_probe(adapter, &at24c02_addr_data, at24c02_detect);

2. at24c02_2.c
  
   at24c02_test r
   at24c02_test w 0x12
   at24c02_test r          /* 可以读出0x12 */

3. at24c02_2.c
   at24c02_test r
   at24c02_test w abcdef
   at24c02_test r          /* 可以读出"abcdef" */