linux中OTG识别到一个U盘后产生一个sg节点的全过程

static int __init usb_init(void)
{
...
	retval = usb_hub_init();//注册hub驱动
...
}　　

static struct usb_driver hub_driver = {
	.name =		"hub",
...
};

int usb_hub_init(void)
{
	if (usb_register(&hub_driver) < 0) {
		printk(KERN_ERR "%s: can‘t register hub driver\n",
			usbcore_name);
		return -1;
	}
...
}

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

int usb_register_driver(struct usb_driver *new_driver, struct module *owner,
			const char *mod_name)
{
...
	new_driver->drvwrap.driver.name = (char *) new_driver->name;
	new_driver->drvwrap.driver.bus = &usb_bus_type;
	new_driver->drvwrap.driver.probe = usb_probe_interface;
...
	retval = driver_register(&new_driver->drvwrap.driver);
	if (retval)
		goto out;
...
}
EXPORT_SYMBOL_GPL(usb_register_driver);　

int driver_register(struct device_driver *drv)
{
...
	ret = bus_add_driver(drv);
...
}

int bus_add_driver(struct device_driver *drv)
{
...
	error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,
				     "%s", drv->name);
...

	klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
...	
　　　　 module_add_driver(drv->owner, drv);
...

}

static int __init usb_init(void)
{
...
	retval = usb_register_device_driver(&usb_generic_driver, THIS_MODULE);
...
}

int usb_register_device_driver(struct usb_device_driver *new_udriver,
		struct module *owner)
{
...
	new_udriver->drvwrap.driver.name = (char *) new_udriver->name;
	new_udriver->drvwrap.driver.bus = &usb_bus_type;
	new_udriver->drvwrap.driver.probe = usb_probe_device;
...
	retval = driver_register(&new_udriver->drvwrap.driver);

...
}
EXPORT_SYMBOL_GPL(usb_register_device_driver);

static struct usb_driver usb_storage_driver = {
	.name =		"usb-storage",
...
};

module_usb_driver(usb_storage_driver);

#define module_usb_driver(__usb_driver) 	module_driver(__usb_driver, usb_register, 		       usb_deregister)

#define module_driver(__driver, __register, __unregister, ...) static int __init __driver##_init(void) { 	return __register(&(__driver) , ##__VA_ARGS__); } module_init(__driver##_init); static void __exit __driver##_exit(void) { 	__unregister(&(__driver) , ##__VA_ARGS__); } module_exit(__driver##_exit);　　

int usb_hub_init(void)
{
...
	khubd_task = kthread_run(hub_thread, NULL, "khubd");
...
}

static int hub_thread(void *__unused)
{
...
	do {
		hub_events();
		wait_event_freezable(khubd_wait,
				!list_empty(&hub_event_list) ||
				kthread_should_stop());
	} while (!kthread_should_stop() || !list_empty(&hub_event_list));
...
}

static void hub_events(void)
{
...
	while (1) {
...　　　　　　　　　　　　
　　　　　　　　　　　　   hdev = hub->hdev; //这里有一段获取usb驱动设备过程，忽略，因为我还没仔细研究过

...
			if (connect_change)
				hub_port_connect_change(hub, i,
						portstatus, portchange);
		}
...
}

static void hub_port_connect_change(struct usb_hub *hub, int port1,
					u16 portstatus, u16 portchange)
{
...
		/* Run it through the hoops (find a driver, etc) */
		if (!status) {
			status = usb_new_device(udev);
...
}

int usb_new_device(struct usb_device *udev)
{
...
	err = device_add(&udev->dev);
...
}

int device_add(struct device *dev)
{
...
	bus_probe_device(dev);
...
}

void bus_probe_device(struct device *dev)
{
...
		ret = device_attach(dev);
...
}

int device_attach(struct device *dev)
{
...
		ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
...
}

int bus_for_each_drv(struct bus_type *bus, struct device_driver *start,
		     void *data, int (*fn)(struct device_driver *, void *))
{
...
		error = fn(drv, data);
...
}

static int __device_attach(struct device_driver *drv, void *data)
{
...
	return driver_probe_device(drv, dev);
}

int driver_probe_device(struct device_driver *drv, struct device *dev)
{
...
	ret = really_probe(dev, drv);
....
}

static int really_probe(struct device *dev, struct device_driver *drv)
{
...
	} else if (drv->probe) {
		ret = drv->probe(dev);
		if (ret)
			goto probe_failed;
	}
...
}

int usb_register_device_driver(struct usb_device_driver *new_udriver,
		struct module *owner)
{
...
	new_udriver->drvwrap.driver.probe = usb_probe_device;
...
}

static int usb_probe_device(struct device *dev)
{
	struct usb_device_driver *udriver = to_usb_device_driver(dev->driver);
...
		error = udriver->probe(udev);
...
}

#define	to_usb_device_driver(d) container_of(d, struct usb_device_driver, 		drvwrap.driver)

retval = usb_register_device_driver(&usb_generic_driver, THIS_MODULE);

struct usb_device_driver usb_generic_driver = {
	.name =	"usb",
	.probe = generic_probe,
...
};

static int generic_probe(struct usb_device *udev)
{
...
			err = usb_set_configuration(udev, c);
...
}

int usb_set_configuration(struct usb_device *dev, int configuration)
{
...
		ret = device_add(&intf->dev);
...
}

static int usb_probe_interface(struct device *dev)
{
　　    struct usb_driver *driver = to_usb_driver(dev->driver);
...
	error = driver->probe(intf, id);
...
}

static int storage_probe(struct usb_interface *intf,
			 const struct usb_device_id *id)
{
...
　　　　 result = usb_stor_probe1(&us, intf, id, unusual_dev);
...
	result = usb_stor_probe2(us);
...
}

static struct usb_driver usb_storage_driver = {
	.name =		"usb-storage",
　　　　 .probe = storage_probe,
...
};

int usb_stor_probe1(struct us_data **pus,
		struct usb_interface *intf,
		const struct usb_device_id *id,
		struct us_unusual_dev *unusual_dev)
{
...
	INIT_DELAYED_WORK(&us->scan_dwork, usb_stor_scan_dwork);
...
}

int usb_stor_probe2(struct us_data *us)
{
...
	queue_delayed_work(system_freezable_wq, &us->scan_dwork,
			delay_use * HZ);
...
}

static void usb_stor_scan_dwork(struct work_struct *work)
{
...
	scsi_scan_host(us_to_host(us));
...
}

void scsi_scan_host(struct Scsi_Host *shost)
{
...
	async_schedule(do_scan_async, data);
...
}

static void do_scan_async(void *_data, async_cookie_t c)
{
...
	scsi_finish_async_scan(data);
}

static void scsi_finish_async_scan(struct async_scan_data *data)
{
...
	scsi_sysfs_add_devices(shost);
...
}

static void scsi_sysfs_add_devices(struct Scsi_Host *shost)
{
...
		if (!scsi_host_scan_allowed(shost) ||
		    scsi_sysfs_add_sdev(sdev) != 0)
			__scsi_remove_device(sdev);
	}
}

int scsi_sysfs_add_sdev(struct scsi_device *sdev)
{
...
	error = device_add(&sdev->sdev_dev);
...
} 

int device_add(struct device *dev)
{
...
			if (class_intf->add_dev)
				class_intf->add_dev(dev, class_intf);
...
}　　

static int __init
init_sg(void)
{
...
	rc = scsi_register_interface(&sg_interface);
...
}

static struct class_interface sg_interface = {
	.add_dev	= sg_add,
	.remove_dev	= sg_remove,
};

static int
sg_add(struct device *cl_dev, struct class_interface *cl_intf)
{
...
	sdp = sg_alloc(disk, scsidp);
...
}

static Sg_device *sg_alloc(struct gendisk *disk, struct scsi_device *scsidp)
{
...
	sprintf(disk->disk_name, "sg%d", k);
...
}