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本文主要分析：
1. i2c设备注册
2. i2c驱动注册
3. 上层调用过程
参考：
http://www.cnblogs.com/helloworldtoyou/p/5126618.html
1. i2c设备注册 kernel/arch/arm/mach-mx6/board-mx6q_sabresd.c static void __init mx6_sabresd_board_init(void) { mxc_iomux_v3_setup_multiple_pads(mx6q_sabresd_pads, ---------------+ ARRAY_SIZE(mx6q_sabresd_pads)); | ... ... | strcpy(mxc_i2c0_board_info[0].type, "wm8962"); | mxc_i2c0_board_info[0].platform_data = &wm8962_config_data; | | //注册i2c总线 | imx6q_add_imx_i2c(0, &mx6q_sabresd_i2c_data); ------------+ | imx6q_add_imx_i2c(1, &mx6q_sabresd_i2c_data); ----+ | | imx6q_add_imx_i2c(2, &mx6q_sabresd_i2c_data); | | | | | | i2c_register_board_info(0, mxc_i2c0_board_info, ----------------+ | ARRAY_SIZE(mxc_i2c0_board_info)); | | | | i2c_register_board_info(1, mxc_i2c1_board_info, | | | | ARRAY_SIZE(mxc_i2c1_board_info)); | | | | i2c_register_board_info(2, mxc_i2c2_board_info, | | | | ARRAY_SIZE(mxc_i2c2_board_info)); | | | | ... ... | | | | } | | | | | | | | static iomux_v3_cfg_t mx6q_sabresd_pads[] = { <----------|-----|--+ /* I2C1, WM8958 */ | | | MX6Q_PAD_CSI0_DAT8__I2C1_SDA, | | | MX6Q_PAD_CSI0_DAT9__I2C1_SCL, | | | | | | /* I2C2, Camera, MIPI */ | | | MX6Q_PAD_KEY_COL3__I2C2_SCL, | | | MX6Q_PAD_KEY_ROW3__I2C2_SDA, | | | | | | #ifdef CONFIG_MX6_ENET_IRQ_TO_GPIO | | | MX6Q_PAD_GPIO_6__OBSERVE_MUX_OBSRV_INT_OUT1, | | | #else | | | /* I2C3 */ | | | MX6Q_PAD_GPIO_3__I2C3_SCL, /* GPIO1[3] */ | | | MX6Q_PAD_GPIO_6__I2C3_SDA, | | | #endif | | | }; | | | | | | //总线速率 V | | static struct imxi2c_platform_data mx6q_sabresd_i2c_data = { | | .bitrate = 100000, | | }; | | | | #define imx6q_add_imx_i2c(id, pdata) \ <-----------+ | imx_add_imx_i2c(&imx6q_imx_i2c_data[id], pdata) | | | | struct platform_device *__init imx_add_imx_i2c( <-----------+ | const struct imx_imx_i2c_data *data, | const struct imxi2c_platform_data *pdata) | { | struct resource res[] = { | { | .start = data->iobase, | .end = data->iobase + data->iosize - 1, | .flags = IORESOURCE_MEM, | }, { | .start = data->irq, | .end = data->irq, | .flags = IORESOURCE_IRQ, | }, | }; | | return imx_add_platform_device("imx-i2c", data->id, | res, ARRAY_SIZE(res), | pdata, sizeof(*pdata)); | } | | //指定i2c链接设备的名称，和地址 | static struct i2c_board_info mxc_i2c0_board_info[] __initdata = { <-+ { | I2C_BOARD_INFO("wm89**", 0x1a), | }, | /* | { | I2C_BOARD_INFO("ov564x", 0x3c), | .platform_data = (void *)&camera_data, | }, | { | I2C_BOARD_INFO("mma8451", 0x1d), | .platform_data = (void *)&mma8451_position, | }, | { | I2C_BOARD_INFO("isl1208", 0x6f), | }, | */ | }; | | int __init | i2c_register_board_info(int busnum, <------------------+ struct i2c_board_info const *info, unsigned len) { int status; down_write(&__i2c_board_lock); //动态更新总线个数 /* dynamic bus numbers will be assigned after the last static one */ if (busnum >= __i2c_first_dynamic_bus_num) __i2c_first_dynamic_bus_num = busnum + 1; //将同一个i2c接口的所有设备都添加到一个链表中 for (status = 0; len; len--, info++) { struct i2c_devinfo *devinfo; devinfo = kzalloc(sizeof(*devinfo), GFP_KERNEL); if (!devinfo) { pr_debug("i2c-core: can‘t register boardinfo!\n"); status = -ENOMEM; break; } devinfo->busnum = busnum; devinfo->board_info = *info; list_add_tail(&devinfo->list, &__i2c_board_list); } up_write(&__i2c_board_lock); return status; } 2. i2c驱动注册 kernel/drivers/i2c/busses/i2c-imx.c static int __init i2c_adap_imx_init(void) { return platform_driver_probe(&i2c_imx_driver, i2c_imx_probe); ----------+ } | | int __init_or_module platform_driver_probe(struct platform_driver *drv, | int (*probe)(struct platform_device *)) | { | int retval, code; | | drv->driver.suppress_bind_attrs = true; | //指定驱动的probe函数 | drv->probe = probe; | //注册平台驱动 | retval = code = platform_driver_register(drv); | | spin_lock(&drv->driver.bus->p->klist_drivers.k_lock); | drv->probe = NULL; | if (code == 0 && list_empty(&drv->driver.p->klist_devices.k_list)) | retval = -ENODEV; | drv->driver.probe = platform_drv_probe_fail; | spin_unlock(&drv->driver.bus->p->klist_drivers.k_lock); | | if (code != retval) | platform_driver_unregister(drv); | return retval; | } | EXPORT_SYMBOL_GPL(platform_driver_probe); | | static struct platform_driver i2c_imx_driver = { <-----------------+ .remove = __exit_p(i2c_imx_remove), | .driver = { | .name = DRIVER_NAME, // "imx-i2c" | .owner = THIS_MODULE, | } | }; | | static int __init i2c_imx_probe(struct platform_device *pdev) <---------+ { struct imx_i2c_struct *i2c_imx; struct resource *res; struct imxi2c_platform_data *pdata; void __iomem *base; resource_size_t res_size; int irq; int ret; dev_dbg(&pdev->dev, "<%s>\n", __func__); //获得i2c寄存器地址的信息 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); if (!res) { dev_err(&pdev->dev, "can‘t get device resources\n"); return -ENOENT; } irq = platform_get_irq(pdev, 0); if (irq < 0) { dev_err(&pdev->dev, "can‘t get irq number\n"); return -ENOENT; } pdata = pdev->dev.platform_data; if (pdata && pdata->init) { ret = pdata->init(&pdev->dev); if (ret) return ret; } res_size = resource_size(res); if (!request_mem_region(res->start, res_size, DRIVER_NAME)) { ret = -EBUSY; goto fail0; } base = ioremap(res->start, res_size); if (!base) { dev_err(&pdev->dev, "ioremap failed\n"); ret = -EIO; goto fail1; } i2c_imx = kzalloc(sizeof(struct imx_i2c_struct), GFP_KERNEL); if (!i2c_imx) { dev_err(&pdev->dev, "can‘t allocate interface\n"); ret = -ENOMEM; goto fail2; } /* Setup i2c_imx driver structure */ strcpy(i2c_imx->adapter.name, pdev->name); i2c_imx->adapter.owner = THIS_MODULE; i2c_imx->adapter.algo = &i2c_imx_algo; // i2c算法 ---------------+ i2c_imx->adapter.dev.parent = &pdev->dev; | i2c_imx->adapter.nr = pdev->id; | i2c_imx->irq = irq; | i2c_imx->base = base; | i2c_imx->res = res; | | /* Get I2C clock */ | i2c_imx->clk = clk_get(&pdev->dev, "i2c_clk"); | if (IS_ERR(i2c_imx->clk)) { | ret = PTR_ERR(i2c_imx->clk); | dev_err(&pdev->dev, "can‘t get I2C clock\n"); | goto fail3; | } | | /* Request IRQ */ | ret = request_irq(i2c_imx->irq, i2c_imx_isr, 0, pdev->name, i2c_imx); | if (ret) { | dev_err(&pdev->dev, "can‘t claim irq %d\n", i2c_imx->irq); | goto fail4; | } | | /* Init queue */ | init_waitqueue_head(&i2c_imx->queue); | | /* Set up adapter data */ | i2c_set_adapdata(&i2c_imx->adapter, i2c_imx); | | /* Set up clock divider */ | if (pdata && pdata->bitrate) | i2c_imx_set_clk(i2c_imx, pdata->bitrate); | else | i2c_imx_set_clk(i2c_imx, IMX_I2C_BIT_RATE); | | /* Set up chip registers to defaults */ | writeb(0, i2c_imx->base + IMX_I2C_I2CR); | writeb(0, i2c_imx->base + IMX_I2C_I2SR); | //添加adapter，一个i2c对应一个adapter | /* Add I2C adapter */ | ret = i2c_add_numbered_adapter(&i2c_imx->adapter); -----------------+ | if (ret < 0) { | | dev_err(&pdev->dev, "registration failed\n"); | | goto fail5; | | } | | | | /* Set up platform driver data */ | | platform_set_drvdata(pdev, i2c_imx); | | | | dev_dbg(&i2c_imx->adapter.dev, "claimed irq %d\n", i2c_imx->irq); | | dev_dbg(&i2c_imx->adapter.dev, "device resources from 0x%x to 0x%x\n",| | i2c_imx->res->start, i2c_imx->res->end); | | dev_dbg(&i2c_imx->adapter.dev, "allocated %d bytes at 0x%x \n", | | res_size, i2c_imx->res->start); | | dev_dbg(&i2c_imx->adapter.dev, "adapter name: \"%s\"\n", | | i2c_imx->adapter.name); | | dev_dbg(&i2c_imx->adapter.dev, "IMX I2C adapter registered\n"); | | | | return 0; /* Return OK */ | | | | fail5: | | free_irq(i2c_imx->irq, i2c_imx); | | fail4: | | clk_put(i2c_imx->clk); | | fail3: | | kfree(i2c_imx); | | fail2: | | iounmap(base); | | fail1: | | release_mem_region(res->start, resource_size(res)); | | fail0: | | if (pdata && pdata->exit) | | pdata->exit(&pdev->dev); | | return ret; /* Return error number */ | | } | |
| | kernel/drivers/i2c/i2c-core.c | | int i2c_add_numbered_adapter(struct i2c_adapter *adap) <----------+ | { | int id; | int status; | | if (adap->nr & ~MAX_ID_MASK) | return -EINVAL; | | retry: | if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0) | return -ENOMEM; | | mutex_lock(&core_lock); | /* "above" here means "above or equal to", sigh; | * we need the "equal to" result to force the result | */ | status = idr_get_new_above(&i2c_adapter_idr, adap, adap->nr, &id); | if (status == 0 && id != adap->nr) { | status = -EBUSY; | idr_remove(&i2c_adapter_idr, id); | } | mutex_unlock(&core_lock); | if (status == -EAGAIN) | goto retry; | | if (status == 0) | status = i2c_register_adapter(adap); ---------------+ | return status; | | } | | EXPORT_SYMBOL_GPL(i2c_add_numbered_adapter); | | | | static int i2c_register_adapter(struct i2c_adapter *adap) <--+ | { | int res = 0; | | /* Can‘t register until after driver model init */ | if (unlikely(WARN_ON(!i2c_bus_type.p))) { | res = -EAGAIN; | goto out_list; | } | | /* Sanity checks */ | if (unlikely(adap->name[0] == ‘\0‘)) { | pr_err("i2c-core: Attempt to register an adapter with " | "no name!\n"); | return -EINVAL; | } | if (unlikely(!adap->algo)) { | pr_err("i2c-core: Attempt to register adapter ‘%s‘ with " | "no algo!\n", adap->name); | return -EINVAL; | } | | rt_mutex_init(&adap->bus_lock); | mutex_init(&adap->userspace_clients_lock); | INIT_LIST_HEAD(&adap->userspace_clients); | | /* Set default timeout to 1 second if not already set */ | if (adap->timeout == 0) | adap->timeout = HZ; | //设置设备名，这里就是/dev显示的 /dev/i2c-1, /dev/i2c-2... | dev_set_name(&adap->dev, "i2c-%d", adap->nr); | adap->dev.bus = &i2c_bus_type; | adap->dev.type = &i2c_adapter_type; | res = device_register(&adap->dev); | if (res) | goto out_list; | | dev_dbg(&adap->dev, "adapter [%s] registered\n", adap->name); | | #ifdef CONFIG_I2C_COMPAT | res = class_compat_create_link(i2c_adapter_compat_class, &adap->dev, | adap->dev.parent); | if (res) | dev_warn(&adap->dev, | "Failed to create compatibility class link\n"); | #endif | | /* create pre-declared device nodes */ | if (adap->nr < __i2c_first_dynamic_bus_num) | i2c_scan_static_board_info(adap); | | /* Notify drivers */ | mutex_lock(&core_lock); | bus_for_each_drv(&i2c_bus_type, NULL, adap, __process_new_adapter); | mutex_unlock(&core_lock); | | return 0; | | out_list: | mutex_lock(&core_lock); | idr_remove(&i2c_adapter_idr, adap->nr); | mutex_unlock(&core_lock); | return res; | } | kernel/driver/i2c/busses/i2c-imx.c | static struct i2c_algorithm i2c_imx_algo = { <--------------------+ .master_xfer = i2c_imx_xfer, ----------------------------------+ .functionality = i2c_imx_func, | }; | static u32 i2c_imx_func(struct i2c_adapter *adapter) | { | return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL; | } | //发送接收会调用的函数 | static int i2c_imx_xfer(struct i2c_adapter *adapter, <---------------------+ struct i2c_msg *msgs, int num) | { | unsigned int i, temp; | int result; | struct imx_i2c_struct *i2c_imx = i2c_get_adapdata(adapter); | | dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__); | | /* Start I2C transfer */ | result = i2c_imx_start(i2c_imx); | if (result) | goto fail0; | | /* read/write data */ | for (i = 0; i < num; i++) { | if (i) { | dev_dbg(&i2c_imx->adapter.dev, | "<%s> repeated start\n", __func__); | temp = readb(i2c_imx->base + IMX_I2C_I2CR); | temp |= I2CR_RSTA; | writeb(temp, i2c_imx->base + IMX_I2C_I2CR); | result = i2c_imx_bus_busy(i2c_imx, 1); | if (result) | goto fail0; | } | dev_dbg(&i2c_imx->adapter.dev, | "<%s> transfer message: %d\n", __func__, i); | /* write/read data */ | #ifdef CONFIG_I2C_DEBUG_BUS | temp = readb(i2c_imx->base + IMX_I2C_I2CR); | dev_dbg(&i2c_imx->adapter.dev, "<%s> CONTROL: IEN=%d, IIEN=%d, " | "MSTA=%d, MTX=%d, TXAK=%d, RSTA=%d\n", __func__, | (temp & I2CR_IEN ? 1 : 0), (temp & I2CR_IIEN ? 1 : 0), | (temp & I2CR_MSTA ? 1 : 0), (temp & I2CR_MTX ? 1 : 0), | (temp & I2CR_TXAK ? 1 : 0), (temp & I2CR_RSTA ? 1 : 0)); | temp = readb(i2c_imx->base + IMX_I2C_I2SR); | dev_dbg(&i2c_imx->adapter.dev, | "<%s> STATUS: ICF=%d, IAAS=%d, IBB=%d, " | "IAL=%d, SRW=%d, IIF=%d, RXAK=%d\n", __func__, | (temp & I2SR_ICF ? 1 : 0), (temp & I2SR_IAAS ? 1 : 0), | (temp & I2SR_IBB ? 1 : 0), (temp & I2SR_IAL ? 1 : 0), | (temp & I2SR_SRW ? 1 : 0), (temp & I2SR_IIF ? 1 : 0), | (temp & I2SR_RXAK ? 1 : 0)); | #endif | if (msgs[i].flags & I2C_M_RD) | result = i2c_imx_read(i2c_imx, &msgs[i]); | else | result = i2c_imx_write(i2c_imx, &msgs[i]); | if (result) | goto fail0; | } | | fail0: | /* Stop I2C transfer */ | i2c_imx_stop(i2c_imx); | | dev_dbg(&i2c_imx->adapter.dev, "<%s> exit with: %s: %d\n", __func__, | (result < 0) ? "error" : "success msg", | (result < 0) ? result : num); | return (result < 0) ? result : num; | } | | // i2c_msg记录了i2c地址 | struct i2c_msg { | __u16 addr; /* slave address */ | __u16 flags; | #define I2C_M_TEN 0x0010 /* this is a ten bit chip address */ | #define I2C_M_RD 0x0001 /* read data, from slave to master */ | #define I2C_M_NOSTART 0x4000 /* if I2C_FUNC_PROTOCOL_MANGLING */ | #define I2C_M_REV_DIR_ADDR 0x2000 /* if I2C_FUNC_PROTOCOL_MANGLING */ | #define I2C_M_IGNORE_NAK 0x1000 /* if I2C_FUNC_PROTOCOL_MANGLING */ | #define I2C_M_NO_RD_ACK 0x0800 /* if I2C_FUNC_PROTOCOL_MANGLING */ | #define I2C_M_RECV_LEN 0x0400 /* length will be first received byte */| __u16 len; /* msg length */ | __u8 *buf; /* pointer to msg data */ | }; | | | 3. 上层应用调用 | kernel/driver/i2c/busses/i2c-dev.c | static int __init i2c_dev_init(void) | { | int res; | | printk(KERN_INFO "i2c /dev entries driver\n"); | | res = register_chrdev(I2C_MAJOR, "i2c", &i2cdev_fops); ------------+ | if (res) | | goto out; | | | | i2c_dev_class = class_create(THIS_MODULE, "i2c-dev"); | | if (IS_ERR(i2c_dev_class)) { | | res = PTR_ERR(i2c_dev_class); | | goto out_unreg_chrdev; | | } | | | | /* Keep track of adapters which will be added or removed later */ | | res = bus_register_notifier(&i2c_bus_type, &i2cdev_notifier); | | if (res) | | goto out_unreg_class; | | | | /* Bind to already existing adapters right away */ | | i2c_for_each_dev(NULL, i2cdev_attach_adapter); | | | | return 0; | | | | out_unreg_class: | | class_destroy(i2c_dev_class); | | out_unreg_chrdev: | | unregister_chrdev(I2C_MAJOR, "i2c"); | | out: | | printk(KERN_ERR "%s: Driver Initialisation failed\n", __FILE__); | | return res; | | } | | static const struct file_operations i2cdev_fops = { <-------------+ | .owner = THIS_MODULE, | .llseek = no_llseek, | .read = i2cdev_read, ----------+ | .write = i2cdev_write, | | .unlocked_ioctl = i2cdev_ioctl, | | .open = i2cdev_open, | | .release = i2cdev_release, | | }; | | V | static ssize_t i2cdev_read(struct file *file, char __user *buf, size_t count, | loff_t *offset) | { | char *tmp; | int ret; | | struct i2c_client *client = file->private_data; | | if (count > 8192) | count = 8192; | | tmp = kmalloc(count, GFP_KERNEL); | if (tmp == NULL) | return -ENOMEM; | | pr_debug("i2c-dev: i2c-%d reading %zu bytes.\n", | iminor(file->f_path.dentry->d_inode), count); | | ret = i2c_master_recv(client, tmp, count); ---------------+ | if (ret >= 0) | | ret = copy_to_user(buf, tmp, count) ? -EFAULT : ret; | | kfree(tmp); | | return ret; | | } | | V | int i2c_master_recv(const struct i2c_client *client, char *buf, int count) | { | struct i2c_adapter *adap = client->adapter; | struct i2c_msg msg; | int ret; | | msg.addr = client->addr; //地址 | msg.flags = client->flags & I2C_M_TEN; //判断是否使用10位地址 | msg.flags |= I2C_M_RD; //读操作 | msg.len = count; //发送个数 | msg.buf = buf; //发送数据 | | ret = i2c_transfer(adap, &msg, 1); ---------------------------+ | | | /* If everything went ok (i.e. 1 msg transmitted), return #bytes | | transmitted, else error code. */ | | return (ret == 1) ? count : ret; | | } | | | | int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num) <--+ | { | unsigned long orig_jiffies; | int ret, try; | | /* REVISIT the fault reporting model here is weak: | * | * - When we get an error after receiving N bytes from a slave, | * there is no way to report "N". | * | * - When we get a NAK after transmitting N bytes to a slave, | * there is no way to report "N" ... or to let the master | * continue executing the rest of this combined message, if | * that‘s the appropriate response. | * | * - When for example "num" is two and we successfully complete | * the first message but get an error part way through the | * second, it‘s unclear whether that should be reported as | * one (discarding status on the second message) or errno | * (discarding status on the first one). | */ | //判断master_xfer函数指针是否存在，存在的话就是指向i2c_imx_xfer | if (adap->algo->master_xfer) { <-----------+ #ifdef DEBUG | for (ret = 0; ret < num; ret++) { | dev_dbg(&adap->dev, "master_xfer[%d] %c, addr=0x%02x, " | "len=%d%s\n", ret, (msgs[ret].flags & I2C_M_RD) | ? ‘R‘ : ‘W‘, msgs[ret].addr, msgs[ret].len, | (msgs[ret].flags & I2C_M_RECV_LEN) ? "+" : ""); | } | #endif | | if (in_atomic() || irqs_disabled()) { | ret = i2c_trylock_adapter(adap); | if (!ret) | /* I2C activity is ongoing. */ | return -EAGAIN; | } else { | i2c_lock_adapter(adap); | } | | /* Retry automatically on arbitration loss */ | orig_jiffies = jiffies; | for (ret = 0, try = 0; try <= adap->retries; try++) { | //调用 i2c_imx_xfer函数 | ret = adap->algo->master_xfer(adap, msgs, num); <---------+ if (ret != -EAGAIN) break; if (time_after(jiffies, orig_jiffies + adap->timeout)) break; } i2c_unlock_adapter(adap); return ret; } else { dev_dbg(&adap->dev, "I2C level transfers not supported\n"); return -EOPNOTSUPP; } } //同理write函数也是一样 static ssize_t i2cdev_write(struct file *file, const char __user *buf, size_t count, loff_t *offset) { int ret; char *tmp; struct i2c_client *client = file->private_data; if (count > 8192) count = 8192; tmp = memdup_user(buf, count); if (IS_ERR(tmp)) return PTR_ERR(tmp); pr_debug("i2c-dev: i2c-%d writing %zu bytes.\n", iminor(file->f_path.dentry->d_inode), count); ret = i2c_master_send(client, tmp, count); -----------+ kfree(tmp); | return ret; | } | V int i2c_master_send(const struct i2c_client *client, const char *buf, int count) { int ret; struct i2c_adapter *adap = client->adapter; struct i2c_msg msg; msg.addr = client->addr; msg.flags = client->flags & I2C_M_TEN; msg.len = count; msg.buf = (char *)buf; ret = i2c_transfer(adap, &msg, 1); /* If everything went ok (i.e. 1 msg transmitted), return #bytes transmitted, else error code. */ return (ret == 1) ? count : ret; }
kernel/drivers/i2c/busses/i2c-imx.c
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原文地址：http://www.cnblogs.com/helloworldtoyou/p/5386580.html
