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_PMstatic 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" */

来源：http://blog.csdn.net/huang879135/article/details/6632960