linux powerpc i2c驱动 之 i2c设备层的注册过程

 

Linux下i2c驱动的加载过程，分为i2c设备层、i2c adapter层与i2c核心层

i2c设备驱动层也就是我们为特定i2c设备编写的驱动，下面是我自己理解的i2c驱动的注册过程

在我们写的i2c设备驱动中，我们会调用i2c_add_driver()开始i2c设备驱动的注册，该函数调用i2c_register_driver完成所有注册操作

 

 

static inline int i2c_add_driver(struct i2c_driver *driver){return i2c_register_driver(THIS_MODULE, driver);}

i2c_register_driver会调用driver_register() 来将设备驱动添加到总线的设备驱动链表中：

int i2c_register_driver(struct module *owner, struct i2c_driver *driver){int res;/* Can't register until after driver model init */if (unlikely(WARN_ON(!i2c_bus_type.p)))return -EAGAIN;driver->driver.owner = owner;driver->driver.bus = &i2c_bus_type;/* When registration returns, the driver core * will have called probe() for all matching-but-unbound devices. */res = driver_register(&driver->driver);if (res)return res;pr_debug("i2c-core: driver [%s] registered\n", driver->driver.name);INIT_LIST_HEAD(&driver->clients);/* Walk the adapters that are already present */mutex_lock(&core_lock);bus_for_each_dev(&i2c_bus_type, NULL, driver, __attach_adapter);mutex_unlock(&core_lock);return 0;}

在driver_register中，通过driver_find来判断驱动是否已经注册，然后会调用

bus_add_drive

将设备驱动添加到总线上

int driver_register(struct device_driver *drv){int ret;struct device_driver *other;BUG_ON(!drv->bus->p);if ((drv->bus->probe && drv->probe) ||    (drv->bus->remove && drv->remove) ||    (drv->bus->shutdown && drv->shutdown))printk(KERN_WARNING "Driver '%s' needs updating - please use ""bus_type methods\n", drv->name);other = driver_find(drv->name, drv->bus);if (other) {put_driver(other);printk(KERN_ERR "Error: Driver '%s' is already registered, ""aborting...\n", drv->name);return -EBUSY;}ret = bus_add_driver(drv);if (ret)return ret;ret = driver_add_groups(drv, drv->groups);if (ret)bus_remove_driver(drv);return ret;}

在bus_add_driver中初始化priv->klist_devices的值，并将priv赋值给drv->p

通过调用klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers)将驱动信息保存到总线结构中，在此之前将调用driver_attach()

int bus_add_driver(struct device_driver *drv){struct bus_type *bus;struct driver_private *priv;int error = 0;bus = bus_get(drv->bus);if (!bus)return -EINVAL;pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name);priv = kzalloc(sizeof(*priv), GFP_KERNEL);if (!priv) {error = -ENOMEM;goto out_put_bus;}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);if (error)goto out_unregister;if (drv->bus->p->drivers_autoprobe) {error = driver_attach(drv);if (error)goto out_unregister;}klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);module_add_driver(drv->owner, drv);error = driver_create_file(drv, &driver_attr_uevent);if (error) {printk(KERN_ERR "%s: uevent attr (%s) failed\n",__func__, drv->name);}error = driver_add_attrs(bus, drv);if (error) {/* How the hell do we get out of this pickle? Give up */printk(KERN_ERR "%s: driver_add_attrs(%s) failed\n",__func__, drv->name);}if (!drv->suppress_bind_attrs) {error = add_bind_files(drv);if (error) {/* Ditto */printk(KERN_ERR "%s: add_bind_files(%s) failed\n",__func__, drv->name);}}kobject_uevent(&priv->kobj, KOBJ_ADD);return 0;out_unregister:kfree(drv->p);drv->p = NULL;kobject_put(&priv->kobj);out_put_bus:bus_put(bus);return error;}

在driver_attach中，通过调用bus_for_each_dev，遍历在总线上挂载的所有设备，并对每个设备(dev)调用__driver_attach()

int driver_attach(struct device_driver *drv){return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);}

在__driver_attach里会调用driver_match_device()来判断dev与driv的id是否相同，在i2c驱动里就会调用i2c_bus_type->match程序进行判断，

当id相同时，将会调用driver_probe_device()

static int __driver_attach(struct device *dev, void *data){struct device_driver *drv = data;/* * Lock device and try to bind to it. We drop the error * here and always return 0, because we need to keep trying * to bind to devices and some drivers will return an error * simply if it didn't support the device. * * driver_probe_device() will spit a warning if there * is an error. */if (!driver_match_device(drv, dev))return 0;if (dev->parent) /* Needed for USB */down(&dev->parent->sem);down(&dev->sem);if (!dev->driver)driver_probe_device(drv, dev);up(&dev->sem);if (dev->parent)up(&dev->parent->sem);return 0;}

在driver_probe_device(),首先会调用device_is_registered()判断dev是否注册，若没注册则返回；若已经注册，则调用really_probe

int driver_probe_device(struct device_driver *drv, struct device *dev){int ret = 0;if (!device_is_registered(dev))return -ENODEV;pr_debug("bus: '%s': %s: matched device %s with driver %s\n", drv->bus->name, __func__, dev_name(dev), drv->name);pm_runtime_get_noresume(dev);pm_runtime_barrier(dev);ret = really_probe(dev, drv);pm_runtime_put_sync(dev);return ret;}

在really_probe()里，首先将drv赋值给dev->driver，然后会调用总线的probe函数，在i2c驱动里，

此时将会调用i2c总线的probe函数：i2c_device_probe

static int really_probe(struct device *dev, struct device_driver *drv){int ret = 0;atomic_inc(&probe_count);pr_debug("bus: '%s': %s: probing driver %s with device %s\n", drv->bus->name, __func__, drv->name, dev_name(dev));WARN_ON(!list_empty(&dev->devres_head));dev->driver = drv;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) {//此处调用i2c总线的probe函数ret = dev->bus->probe(dev);if (ret)goto probe_failed;} else if (drv->probe) {ret = drv->probe(dev);if (ret)goto probe_failed;}driver_bound(dev);ret = 1;pr_debug("bus: '%s': %s: bound device %s to driver %s\n", drv->bus->name, __func__, dev_name(dev), drv->name);goto done;probe_failed:devres_release_all(dev);driver_sysfs_remove(dev);dev->driver = NULL;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);}/* * 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;}

在i2c_device_probe()里，会根据to_i2c_driver(dev->driver)获取i2c驱动，也就是我们编写的具体的i2c设备驱动的结构体i2c_driver，即

static struct i2c_driver XXX_driver = {.driver = {.name = "XXXX_name",.owner = THIS_MODULE,},.probe = XXX_probe,.remove = XXX_remove,.id_table = XXX_id,};

这样就调用了我们驱动的probe()了，这就是我们在驱动里调用i2c_add_driver()，通过driver_register()的一系列调用，最后执行我们所写的probe()

static int i2c_device_probe(struct device *dev){struct i2c_client *client = i2c_verify_client(dev);struct i2c_driver *driver;int status;if (!client)return 0;driver = to_i2c_driver(dev->driver);if (!driver->probe || !driver->id_table)return -ENODEV;client->driver = driver;if (!device_can_wakeup(&client->dev))device_init_wakeup(&client->dev,client->flags & I2C_CLIENT_WAKE);dev_dbg(dev, "probe\n");status = driver->probe(client, i2c_match_id(driver->id_table, client));//执行我们写的probe函数if (status)client->driver = NULL;return status;}