I2C子系统之I2C bus初始化——I2C_init()
I2C子系统之I2C bus初始化——I2C_init()
根据前文的分析(
),在linux内核启动的时候最先执行的和I2C子系统相关的函数应该是driver/i2c/i2c-core.c文件中的
i2c_init()函数。下面具体此函数具体做了那些预备工作。
1.i2c总线的注册
i2c_init()的函数实现如下:
- static int __init i2c_init(void)
- {
- ... ...
- retval = bus_register(&i2c_bus_type);
- ... ...
- }
2.i2c_bus_type总线
- 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,
- };
总线提供了match和probe方法:match方法的用来进行client device和client driver的配对。
在向总线i2c_bus_type注册设备或者驱动时会调用此方法。
2.6.37.1中的at24c02采用的是i2c_match_id这种方法,本质上还是通过name来配对。
- static int i2c_device_match(struct device *dev, struct device_driver *drv)
- {
- struct i2c_client *client = i2c_verify_client(dev);
- struct i2c_driver *driver;
- if (!client) //判断当前的dev是否是client类型,假如不是立即返回
- return 0;
- /* Attempt an OF style match */
- if (of_driver_match_device(dev, drv)) //条件drv->of_match_table,对at24来说是at24_driver->drv->of_match_table
- return 1;
- driver = to_i2c_driver(drv);
- /* match on an id table if there is one */
- if (driver->id_table)
- return i2c_match_id(driver->id_table, client) != NULL;
- return 0;
- }
probe方法在完成设备和驱动的配对后调用执行,i2c_bus_type的probe方法是通过传递进来的drv找到
包含此drv的i2c_driver驱动,然后再去调用i2c_driver的probe方法,此处就是at24_probe。为什么要这
样呢?因为driver_register后,注册的是i2_driver->drv,而drv中的probe未初始化,我们需要调用的是
i2c-driver的probe方法。
- 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));
- if (status) {
- client->driver = NULL;
- i2c_set_clientdata(client, NULL);
- }
- return status;
- }
相关阅读:
I2C子系统之at24c02读写测试
I2C子系统之ioctl()
I2C子系统之at24c02简介
I2C子系统之总结
I2C子系统之内核中I2C子系统的结构
I2C子系统之I2C bus初始化——I2C_init()
I2C子系统之platfor_device初始化——smdk2440_machine_init()
I2C子系统之platform_driver初始化——I2C_adap_s3c_init()
I2C子系统之I2C总线时钟频率设置
I2C子系统之adapter device和client device注册——I2C_add_number_adapter()
I2C子系统之__I2C_first_dynamic_bus_num变量的相关分析
I2C子系统之 adapter driver注册——I2C_dev_init()
I2C子系统之write()
评论暂时关闭