驱动加载到I2C总线，如何运行到probe

为了简短文章长度，一些检查和调试信息被删除

1. 在xxx_init()中会调用i2c_add_driver()函数   

static int __init ltr559_init(void){    return i2c_add_driver(&ltr_ps_driver);//ltr_ps_driver是一个struct i2c_driver} static void __exit ltr559_exit(void){    i2c_del_driver(&ltr_ps_driver);    }module_init(ltr559_init);module_exit(ltr559_exit);

2. i2c_add_driver

        是一个宏命令,调用 i2c_register_driver

/*************************  include/linux/i2c.h  *******************************/#define i2c_add_driver(driver) \         i2c_register_driver(THIS_MODULE, driver)

3.  i2c_register_driver

     在一些 i2c_adapter 相关总线实例， 一个 i2c_driver 可以被一个或多个 i2c_client 设备节点使用去访问 i2c_slave_chip

     该函数

/**********************  kernel/drivers/i2c/i2c_core.c   ************************/int i2c_register_driver(struct module *owner, struct i2c_driver *driver){int res;/*在驱动模块初始化完成后才可以注册 */if (unlikely(WARN_ON(!i2c_bus_type.p)))return -EAGAIN;/* 添加该驱动到i2c驱动链表上 */driver->driver.owner = owner; driver->driver.bus = &i2c_bus_type;/* 当注册完成，驱动代码将调用probe()去匹配设备 */res = driver_register(&driver->driver);INIT_LIST_HEAD(&driver->clients);i2c_for_each_dev(driver, __process_new_driver);return 0;}

4. driver_register

    主要的工作还是由 bus_add_driver 来操作

/***************************    kernel/driver/base/driver.c  **************************/int driver_register(struct device_driver *drv){int ret;struct device_driver *other;BUG_ON(!drv->bus->p);other = driver_find(drv->name, drv->bus);//通过driver_name在bus上查找该driver，正常返回0ret = bus_add_driver(drv); //主要ret = driver_add_groups(drv, drv->groups);if (ret) {bus_remove_driver(drv);return ret;}kobject_uevent(&drv->p->kobj, KOBJ_ADD);return ret;}

5. bus_add_driver

/****************  kernel/driver/base/bus.c **********************************/int bus_add_driver(struct device_driver *drv){    struct bus_type *bus;    struct driver_private *priv;    int error = 0;    bus = bus_get(drv->bus);       priv = kzalloc(sizeof(*priv), GFP_KERNEL);     klist_init(&priv->klist_devices, NULL, NULL);    priv->driver = drv;    drv->p = priv;    priv->kobj.kset = bus->p->drivers_kset;    error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,                     "%s", drv->name);       klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);    if (drv->bus->p->drivers_autoprobe) {        error = driver_attach(drv);  //尝试绑定            }    module_add_driver(drv->owner, drv);    error = driver_create_file(drv, &driver_attr_uevent); //为驱动创建文件，继续调用sysfs_create_file()        error = driver_add_attrs(bus, drv);        if (!drv->suppress_bind_attrs) {        error = add_bind_files(drv);            }    return 0;}

6. driver_attach

/** * driver_attach - try to bind driver to devices. * @drv: driver. * * Walk the list of devices that the bus has on it and try to * match the driver with each one.  If driver_probe_device() * returns 0 and the @dev->driver is set, we've found a * compatible pair. */int driver_attach(struct device_driver *drv){return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);}

7. bus_for_each_dev

     参数 fn 就是__driver_attach()函数

/** * bus_for_each_dev - device iterator. * @bus: bus type. * @start: device to start iterating from. * @data: data for the callback. * @fn: function to be called for each device.  */int bus_for_each_dev(struct bus_type *bus, struct device *start,     void *data, int (*fn)(struct device *, void *)){struct klist_iter i;struct device *dev;int error = 0;if (!bus || !bus->p)return -EINVAL;klist_iter_init_node(&bus->p->klist_devices, &i,     (start ? &start->p->knode_bus : NULL));while ((dev = next_device(&i)) && !error)error = fn(dev, data);klist_iter_exit(&i);return error;}

8. __driver_attach

static int __driver_attach(struct device *dev, void *data){struct device_driver *drv = data;if (!driver_match_device(drv, dev))return 0;if (dev->parent)/* 如果是被usb接口调用，父设备也要上锁*/device_lock(dev->parent);device_lock(dev);if (!dev->driver)driver_probe_device(drv, dev); //device_unlock(dev);if (dev->parent)device_unlock(dev->parent);return 0;}

9. driver_probe_device

    如果设备没有注册，则该函数返回 -ENODEV , probe 成功 返回 1 ，失败 返回 0 。该函数被调用时，设备一定要上锁

/**********************  kernel/drivers/base/dd.c ********************************* * driver_probe_device - attempt to bind device & driver together * @drv: driver to bind a device to * @dev: device to try to bind to the driver */int driver_probe_device(struct device_driver *drv, struct device *dev){int ret = 0;if (!device_is_registered(dev))  //判断设备是否注册return -ENODEV;pm_runtime_barrier(dev); ret = really_probe(dev, drv);pm_request_idle(dev);return ret;}

10. really_probe

/**********************  kernel/drivers/base/dd.c *********************************/static int really_probe(struct device *dev, struct device_driver *drv){int ret = 0;atomic_inc(&probe_count);WARN_ON(!list_empty(&dev->devres_head));dev->driver = drv;ret = pinctrl_bind_pins(dev);if (ret)goto probe_failed;if (driver_sysfs_add(dev)) {printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",__func__, dev_name(dev));goto probe_failed;}if (dev->bus->probe) {ret = dev->bus->probe(dev);if (ret)goto probe_failed;} else if (drv->probe) {ret = drv->probe(dev); //这里才是正在调用驱动中实现的probe函数if (ret)goto probe_failed;}driver_bound(dev);ret = 1;goto done;probe_failed:devres_release_all(dev);driver_sysfs_remove(dev);dev->driver = NULL;dev_set_drvdata(dev, NULL);if (ret == -EPROBE_DEFER) {/* Driver requested deferred probing */dev_info(dev, "Driver %s requests probe deferral\n", drv->name);driver_deferred_probe_add(dev);} else if (ret != -ENODEV && ret != -ENXIO) {/* driver matched but the probe failed */printk(KERN_WARNING       "%s: probe of %s failed with error %d\n",       drv->name, dev_name(dev), ret);} else {pr_debug("%s: probe of %s rejects match %d\n",       drv->name, dev_name(dev), ret);}/* * Ignore errors returned by ->probe so that the next driver can try * its luck. */ret = 0;done:atomic_dec(&probe_count);wake_up(&probe_waitqueue);return ret;}