接着上回分解：
上节向系统注册了I2C client设备，光有设备不行啊，还要有驱动才能工作，下面就看他们驱动，还以isa1200马达为例。
static const struct i2c_device_id isa1200_id[] = {
{ "isa1200_1", 0 },
{ },
};
/*isa1200马达的驱动结构体*/
static struct i2c_driver isa1200_driver = {
.driver = {
.name = "isa1200",
},
.probe = isa1200_probe,
.remove = __devexit_p(isa1200_remove),
.suspend = isa1200_suspend,
.resume = isa1200_resume,
.id_table = isa1200_id,
};
/*该驱动结构的注册函数*/
static int __init isa1200_init(void)
{
return i2c_add_driver(&isa1200_driver);
}
module_init(isa1200_init);
下面分析i2c_add_driver(&isa1200_driver)是个这么样的过程。
static inline int i2c_add_driver(struct i2c_driver *driver)
{
return i2c_register_driver(THIS_MODULE, driver);
}
这个函数没什么看的，继续往下跟踪：
int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
{
/*把该驱动挂载到I2C总线上*/
driver->driver.owner = owner;
driver->driver.bus = &i2c_bus_type;
/*向该总线注册该驱动，在注册该驱动时，由于总线有probe函数，所有先调用总线的probe函数*/
res = driver_register(&driver->driver);
/*初始化该driver所支持的client链表*/
INIT_LIST_HEAD(&driver->clients);
/*遍历该I2C总线上的adapter设备，并为每一个设备和该driver调用__process_new_driver函数*/
bus_for_each_dev(&i2c_bus_type, NULL, driver, __process_new_driver);
return 0;
}
遍历的目的是：该驱动支持的设备有可能在不同的adapter上都有。
跟进__process_new_driver函数，看看是什么东东。
static int __process_new_driver(struct device *dev, void *data)
{
/*设备类型必须为i2c_adapter_type*/
if (dev->type != &i2c_adapter_type)
return 0;
return i2c_do_add_adapter(data, to_i2c_adapter(dev));
}
继续分解
static int i2c_do_add_adapter(struct i2c_driver *driver,
struct i2c_adapter *adap)
{
/*该函数马达驱动没有用到*/
i2c_detect(adap, driver);
/*如果该函数不为空，则调用该函数，其实也是空函数*/
if (driver->attach_adapter) {
driver->attach_adapter(adap);
}
return 0;
}
下面看下I2C总线的注册过程：
先看下其结构体：
struct bus_type i2c_bus_type = {
.name = "i2c",
.match = i2c_device_match,
.probe = i2c_device_probe,
.remove = i2c_device_remove,
.shutdown = i2c_device_shutdown,
.pm = &i2c_device_pm_ops,
};
其中总线的probe函数会在，挂载该总线上得驱动和设备匹配的时候调用，驱动的probe函数得不到调用
static int __init i2c_init(void)
{
retval = bus_register(&i2c_bus_type);
}
postcore_initcall(i2c_init);
下面看下i2c_device_probe函数是怎么探测的。
static int i2c_device_probe(struct device *dev)
{
/*从设备找到client*/
struct i2c_client *client = i2c_verify_client(dev);
struct i2c_driver *driver;
/*从设备driver找到该设备的i2c驱动*/
driver = to_i2c_driver(dev->driver);
/*把该I2C的驱动和client的driver绑定*/
client->driver = driver;
/*调用该driver的probe函数*/
status = driver->probe(client, i2c_match_id(driver->id_table, client));
}
关于匹配的过程，是调用总线的match函数：
static int i2c_device_match(struct device *dev, struct device_driver *drv)
{
struct i2c_client *client = i2c_verify_client(dev);
struct i2c_driver *driver;
driver = to_i2c_driver(drv);
/*有client的name与i2c driver的id_table匹配比较*/
if (driver->id_table)
return i2c_match_id(driver->id_table, client) != NULL;
return 0;
}
今天就写到这吧，有空了明天继续写。
