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