基于at91rm9200的i2c分析（DS1307实时时钟芯片）
board-ek.c
构造i2c_board_info结构体
static struct i2c_board_info __initdata ek_i2c_devices[] = {
{
I2C_BOARD_INFO("ds1307", 0x68),
},
};
at91_add_device_i2c(ek_i2c_devices, ARRAY_SIZE(ek_i2c_devices));
->
i2c_register_board_info(0, devices, nr_devices);
->
将i2c_board_info添加到__i2c_board_list，总线0
struct i2c_devinfo *devinfo;
devinfo->busnum = busnum;
devinfo->board_info = *info;
list_add_tail(&devinfo->list, &__i2c_board_list);
注册at91rm9200_twi_device平台device
platform_device_register(&at91rm9200_twi_device);
static struct platform_device at91rm9200_twi_device = {
.name = "at91_i2c",
.id = -1,
.resource = twi_resources,
.num_resources = ARRAY_SIZE(twi_resources),
};
i2c-at91.c
static struct platform_driver at91_i2c_driver = {
.probe = at91_i2c_probe,
.remove = __devexit_p(at91_i2c_remove),
.suspend = at91_i2c_suspend,
.resume = at91_i2c_resume,
.driver = {
.name = "at91_i2c",
.owner = THIS_MODULE,
},
};
注册平台driver
platform_driver_register(&at91_i2c_driver);
当发现device链表有与”at91_i2c“同名的device就调用at91_i2c_probe
at91_i2c_probe->
构造adapter
struct i2c_adapter *adapter;
snprintf(adapter->name, sizeof(adapter->name), "AT91");
adapter->algo = &at91_algorithm;
/* 通信算法 */
clk_enable(twi_clk);
/* enable peripheral clock */
at91_twi_hwinit();
/* initialize TWI controller */
at91_twi_hwinit();
/* initialize TWI controller */
注册adapter
i2c_add_numbered_adapter(adapter)->
i2c_register_adapter(adap)->
device_register(&adap->dev);
/* create pre-declared device nodes */
i2c_scan_static_board_info(adap);
->
list_for_each_entry(devinfo, &__i2c_board_list, list)
如果busnum相等则调用i2c_new_device
if (devinfo->busnum == adapter->nr && !i2c_new_device(adapter, &devinfo->board_info))->
构造client
struct i2c_client *client;
client->adapter = adap;
/* 检查设备地址是否有效 */
i2c_check_client_addr_validity(client);
/* 检查地址是否被占用 */
i2c_check_addr_busy(adap, client->addr);
注册device
device_register(&client->dev);
i2c-dev.c
i2c_dev_init->
申请设备号，并创建cdev，初始化cdev
register_chrdev(I2C_MAJOR, "i2c", &i2cdev_fops);
创建class：/sys/class/i2c-dev
i2c_dev_class = class_create(THIS_MODULE, "i2c-dev");
注册i2c_driver
i2c_add_driver(&i2cdev_driver);
->
i2c_register_driver(THIS_MODULE, driver);
->
注册driver
driver_register(&driver->driver);
在链表i2c_bus_type中遍历每一个device，对每一个device调用__process_new_driver
bus_for_each_dev(&i2c_bus_type, NULL, driver, __process_new_driver);
__process_new_driver->
i2c_do_add_adapter(data, to_i2c_adapter(dev))
调用driver的attach_adapter函数，即i2cdev_attach_adapter
driver->attach_adapter(adap)->
/* 构造i2c_dev */
i2c_dev = get_free_i2c_dev(adap);
->
/* 将i2c_dev添加到i2c_dev_list */
list_add_tail(&i2c_dev->list, &i2c_dev_list);
/* 在/dev/目录下创建设备节点i2c-0 */
i2c_dev->dev = device_create(i2c_dev_class, &adap->dev, MKDEV(I2C_MAJOR, adap->nr), NULL, "i2c-%d", adap->nr);
这样我们就可以通过i2cdev_fops来操作i2c设备了
static const struct file_operations i2cdev_fops = {
.owner = THIS_MODULE,
.llseek = no_llseek,
.read = i2cdev_read,
.write = i2cdev_write,
.unlocked_ioctl = i2cdev_ioctl,
.open = i2cdev_open,
.release = i2cdev_release,
};
我们也可以不通过/dev/i2c-0这种操作方式，单独实现特定的i2c_driver和i2c_client
rtc-ds1307.c
static const struct i2c_device_id ds1307_id[] = {
{ "ds1307", ds_1307 },
{ "ds1337", ds_1337 },
{ "ds1338", ds_1338 },
{ "ds1339", ds_1339 },
{ "ds1388", ds_1388 },
{ "ds1340", ds_1340 },
{ "ds3231", ds_3231 },
{ "m41t00", m41t00 },
{ "rx8025", rx_8025 },
{ }
};
MODULE_DEVICE_TABLE(i2c, ds1307_id);
static struct i2c_driver ds1307_driver = {
.driver = {
.name = "rtc-ds1307",
.owner = THIS_MODULE,
},
.probe = ds1307_probe,
.remove = __devexit_p(ds1307_remove),
.id_table = ds1307_id,
};
i2c_add_driver(&ds1307_driver)->
i2c_register_driver(THIS_MODULE, driver)->
driver->driver.bus = &i2c_bus_type;
注册driver
driver_register(&driver->driver)->
检查driver是否已存在
driver_find(drv->name, drv->bus)->
bus_add_driver(drv)->
driver_attach(drv)->
遍历drv->bus链表上的每一个device，为每一个device调用__driver_attach
bus_for_each_dev(drv->bus, NULL, drv, __driver_attach)->
__driver_attach(struct device *dev, void *data)->
driver_match_device(drv, dev))->
如果总线i2c_bus_type存在match函数则调用match
drv->bus->match ? drv->bus->match(dev, drv) : 1;
i2c-core.c中定义了i2c_bus_type，同时定义了i2c_device_match函数
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,
};
i2c_device_match(struct device *dev, struct device_driver *drv)->
匹配i2c_device_id(ds1307_id)里的名称
i2c_match_id(driver->id_table, client)->
如果匹配成功，继续driver_attach->
driver_probe_device(drv, dev)->
really_probe(dev, drv)->
调用i2c_device_probe
dev->bus->probe(dev)->
struct i2c_driver *driver = to_i2c_driver(dev->driver)
调用ds1307_probe
driver->probe(client, i2c_match_id(driver->id_table, client))->
注册rtcdevice
ds1307->rtc = rtc_device_register(client->name, &client->dev, &ds13xx_rtc_ops, THIS_MODULE)->
注册device
device_register(&rtc->dev);
推荐阅读
- 热闹中的孤独
- JAVA（抽象类与接口的区别&重载与重写&内存泄漏）
- 放屁有这三个特征的，请注意啦！这说明你的身体毒素太多
- 一个人的旅行，三亚
- 布丽吉特，人生绝对的赢家
- 慢慢的美丽
- 尽力
- 一个小故事，我的思考。
- 家乡的那条小河
- 《真与假的困惑》???|《真与假的困惑》??? ——致良知是一种伟大的力量