Linux USB subsystem --- USBFS driver registration

目的：對USB作深入學習，在此留下筆記。歡迎討論。

[Linux 3.2] [driver/usb/core/devio.c]

定義：usbfs_driver

1. struct usb_driver usbfs_driver = {
2. .name = "usbfs",
3. .probe = driver_probe,
4. .disconnect = driver_disconnect,
5. .suspend = driver_suspend,
6. .resume = driver_resume,
7. };

[Linux 3.2] [include/linux/usb.h]

函數：usb_register();

1. /* use a define to avoid include chaining to get THIS_MODULE & friends */
2. #define usb_register(driver) \
3. usb_register_driver(driver, THIS_MODULE, KBUILD_MODNAME)

[Linux 3.2] [driver/usb/core/driver.c]

函數：usb_register_driver();

1. /**
2. * usb_register_driver - register a USB interface driver
3. * @new_driver: USB operations for the interface driver
4. * @owner: module owner of this driver.
5. * @mod_name: module name string
6. *
7. * Registers a USB interface driver with the USB core. The list of
8. * unattached interfaces will be rescanned whenever a new driver is
9. * added, allowing the new driver to attach to any recognized interfaces.
10. * Returns a negative error code on failure and 0 on success.
11. *
12. * NOTE: if you want your driver to use the USB major number, you must call
13. * usb_register_dev() to enable that functionality. This function no longer
14. * takes care of that.
15. */
16. int usb_register_driver(struct usb_driver *new_driver, struct module *owner,
17. const char *mod_name)
18. {
19. int retval = 0;
21. if (usb_disabled())
22. return -ENODEV;
24. new_driver->drvwrap.for_devices = 0;
25. new_driver->drvwrap.driver.name = (char *) new_driver->name;
26. new_driver->drvwrap.driver.bus = &usb_bus_type;
27. new_driver->drvwrap.driver.probe = usb_probe_interface;
28. new_driver->drvwrap.driver.remove = usb_unbind_interface;
29. new_driver->drvwrap.driver.owner = owner;
30. new_driver->drvwrap.driver.mod_name = mod_name;
31. spin_lock_init(&new_driver->dynids.lock);
32. INIT_LIST_HEAD(&new_driver->dynids.list);
34. retval = driver_register(&new_driver->drvwrap.driver);
35. if (retval)
36. goto out;
38. usbfs_update_special();
40. retval = usb_create_newid_file(new_driver);
41. if (retval)
42. goto out_newid;
44. retval = usb_create_removeid_file(new_driver);
45. if (retval)
46. goto out_removeid;
48. pr_info("%s: registered new interface driver %s\n",
49. usbcore_name, new_driver->name);
51. out:
52. return retval;
54. out_removeid:
55. usb_remove_newid_file(new_driver);
56. out_newid:
57. driver_unregister(&new_driver->drvwrap.driver);
59. printk(KERN_ERR "%s: error %d registering interface "
60. " driver %s\n",
61. usbcore_name, retval, new_driver->name);
62. goto out;
63. }

此函數主要功能實現是通過driver_register實現。後面會詳細分析。

其余功能如下：

1. usbfs_update_special() ==> 跟usb文件系統相關，暫時不分析。

2. usb_create_newid_file() ==> 創建newid屬性文件，在/sys/bus/usb/drivers/usbfs/下面可以看到此文件。

3. usb_create_removeid_file() ==> 創建removeid屬性文件，在/sys/bus/usb/drivers/usbfs/下面可以看到此文件。

4. 輸出信息：usbcore: registered new interface driver usbfs

問題：newid與removeid屬性文件的作用是什麼？

回答：等待解答。

現在分析driver_register功能：

1. 首先判斷，些驅動所屬bus的subsys_private結構有沒有初始化。如果沒有，報bug信息。

2. 判斷需要注冊的driver和driver所屬的bus是否都有probe, remove, shutdown函數。如有，打印kernel warning信息。

3. 判斷此driver已經在driver所屬的bus上面注冊過了。如果注冊過了，打印錯誤信息，並返回。

4. 調用bus_add_driver來注冊driver。

5. 調用driver_add_groups來添加組屬性。

6. 返回。

最後對bus_add_driver進行分析。

1. /**
2. * bus_add_driver - Add a driver to the bus.
3. * @drv: driver.
4. */
5. int bus_add_driver(struct device_driver *drv)
6. {
7. struct bus_type *bus;
8. struct driver_private *priv;
9. int error = 0;
11. bus = bus_get(drv->bus);
12. if (!bus)
13. return -EINVAL;
15. pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name);
17. priv = kzalloc(sizeof(*priv), GFP_KERNEL);
18. if (!priv) {
19. error = -ENOMEM;
20. goto out_put_bus;
21. }
22. klist_init(&priv->klist_devices, NULL, NULL);
23. priv->driver = drv;
24. drv->p = priv;
25. priv->kobj.kset = bus->p->drivers_kset;
26. error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,
27. "%s", drv->name);
28. if (error)
29. goto out_unregister;
31. if (drv->bus->p->drivers_autoprobe) {
32. error = driver_attach(drv);
33. if (error)
34. goto out_unregister;
35. }
36. klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
37. module_add_driver(drv->owner, drv);
39. error = driver_create_file(drv, &driver_attr_uevent);
40. if (error) {
41. printk(KERN_ERR "%s: uevent attr (%s) failed\n",
42. __func__, drv->name);
43. }
44. error = driver_add_attrs(bus, drv);
45. if (error) {
46. /* How the hell do we get out of this pickle? Give up */
47. printk(KERN_ERR "%s: driver_add_attrs(%s) failed\n",
48. __func__, drv->name);
49. }
51. if (!drv->suppress_bind_attrs) {
52. error = add_bind_files(drv);
53. if (error) {
54. /* Ditto */
55. printk(KERN_ERR "%s: add_bind_files(%s) failed\n",
56. __func__, drv->name);
57. }
58. }
60. kobject_uevent(&priv->kobj, KOBJ_ADD);
61. return 0;
63. out_unregister:
64. kobject_put(&priv->kobj);
65. kfree(drv->p);
66. drv->p = NULL;
67. out_put_bus:
68. bus_put(bus);
69. return error;
70. }

其功能是向bus中添加一個driver。

1. bus_get() ==> bus的計數加1;

2. kzalloc，分配driver_private內存空間。

3. 初始化此driver的klist_devices鏈表。

4. kobject_init_and_add() ==> 在/sys/bus/usb/drivers/下面創建usbfs文件夾。

5. 如果總線支持drivers_autoprobe，調用driver_attach。（USB 總線支持）

6. driver_create_file ==> 在/sys/bus/usb/drivers/usbfs下面創建uevent屬性文件。

7. driver_add_attrs() ==> 將總線的屬性也加到/sys/bus/usb/drivers/usbfs

8. add_bind_files() ==> 在/sys/bus/usb/drivers/usbfs創建bind和unbind屬性文件。

9. kobject_uevent() ==> 發送一個KOBJ_ADD的事件。

在/sys/bus/usb/drivers/usbfs下面的文件：

bind module new_id remove_id uevent unbind