I2C子系統之adapter device和client device注冊——I2C_add_number_adapter()

如前文所述（http://www.linuxidc.com/Linux/2012-08/68263.htm），在probe函數會調用函數i2c_add_number_adapter()，通過此函數來實現adapter device和client device的注冊

i2c_add_number_adapter()函數如下：

1. int i2c_add_numbered_adapter(struct i2c_adapter *adap)
2. {
3. int id;
4. int status;
6. if (adap->nr & ~MAX_ID_MASK)
7. return -EINVAL;
9. retry:
10. if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0)
11. return -ENOMEM;
13. mutex_lock(&core_lock);
14. /* "above" here means "above or equal to", sigh;
15. * we need the "equal to" result to force the result
16. */
17. status = idr_get_new_above(&i2c_adapter_idr, adap, adap->nr, &id);
18. if (status == 0 && id != adap->nr) {
19. status = -EBUSY;
20. idr_remove(&i2c_adapter_idr, id);
21. }
22. mutex_unlock(&core_lock);
23. if (status == -EAGAIN)
24. goto retry;
26. if (status == 0)
27. status = i2c_register_adapter(adap);
28. return status;
29. }

函數前面部分應該是用來提高搜索效率相關，此處省略分析。直接分析

i2c_register_adapter()函數，如下：

1. static int i2c_register_adapter(struct i2c_adapter *adap)
2. {
3. int res = 0;
5. 。。。 。。。
6. dev_set_name(&adap->dev, "i2c-%d", adap->nr);
7. adap->dev.bus = &i2c_bus_type;
8. adap->dev.type = &i2c_adapter_type;
9. res = device_register(&adap->dev);
10. 。。。 。。。
12. /* create pre-declared device nodes */
13. if (adap->nr < __i2c_first_dynamic_bus_num)
14. i2c_scan_static_board_info(adap);
16. /* Notify drivers */
17. printk("bus_search\n");
18. mutex_lock(&core_lock);
19. bus_for_each_drv(&i2c_bus_type, NULL, adap, __process_new_adapter);
20. mutex_unlock(&core_lock);
22. return 0;
24. out_list:
25. mutex_lock(&core_lock);
26. idr_remove(&i2c_adapter_idr, adap->nr);
27. mutex_unlock(&core_lock);
28. return res;
29. }

1. dev_set_name(&adap->dev, "i2c-%d", adap->nr);
2. adap->dev.bus = &i2c_bus_type;
3. adap->dev.type = &i2c_adapter_type;
4. res = device_register(&adap->dev);

語句，將名為i2c-0的adapter設備注冊到i2c_bus_type型的i2c總線上上，其中通過

1. adap->dev.type = &i2c_adapter_type;