hub_thread

1. 流程图



2. usb_hub_init()

int usb_hub_init(void)
{
	//1. 注册usb hub驱动
	if (usb_register(&hub_driver) < 0) { //注册hub驱动到usb子系统总线上
		printk(KERN_ERR "%s: can't register hub driver\n",
			usbcore_name);
		return -1;
	}

	//2. hub_thread内部是完成设备的枚举,即创建usb设备,最终调用1.中的驱动match完成相应的驱动注册
	khubd_task = kthread_run(hub_thread, NULL, "khubd"); //创建hub内核线程
	if (!IS_ERR(khubd_task))
		return 0;

	/* Fall through if kernel_thread failed */
	usb_deregister(&hub_driver);
	printk(KERN_ERR "%s: can't start khubd\n", usbcore_name);

	return -1;
}

前面已经分析过了hub驱动的注册流程,详见:点击打开链接,这里主要分析hub_thread线程内部的工作原理。

3. hub_thread()

khubd_task = kthread_run(hub_thread, NULL, "khubd"); //创建hub内核线程
static int hub_thread(void *__unused)
{
	/* khubd needs to be freezable to avoid intefering with USB-PERSIST
	 * port handover.  Otherwise it might see that a full-speed device
	 * was gone before the EHCI controller had handed its port over to
	 * the companion full-speed controller.
	 */
	set_freezable();

	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));

	pr_debug("%s: khubd exiting\n", usbcore_name);
	return 0;
}

hub_thread()函数内部的主要工作是等待khubd_wait事件的发生,前提是该事件的条件hub_event_list不为NULL,在ehci主机控制器这一节(详见:点击打开链接, “第5.4 usb_hcd_request_irqs()”)我们分析过是如何唤醒该khubd_wait,等待事件的,这里不再赘述!所以当主机控制器ehci上有设备接入时(如U盘),ehci将唤醒khubd_wait,这里wait_event_freezable()等待事件成立将调用hub_event()事件函数。

4. hub_event()

static void hub_events(void)
{
	struct list_head *tmp;
	struct usb_device *hdev;
	struct usb_interface *intf;
	struct usb_hub *hub;
	struct device *hub_dev;
	u16 hubstatus;
	u16 hubchange;
	u16 portstatus;
	u16 portchange;
	int i, ret;
	int connect_change, wakeup_change;

	/*
	 *  We restart the list every time to avoid a deadlock with
	 * deleting hubs downstream from this one. This should be
	 * safe since we delete the hub from the event list.
	 * Not the most efficient, but avoids deadlocks.
	 */
	while (1) {

		/* Grab the first entry at the beginning of the list */
		spin_lock_irq(&hub_event_lock);
		if (list_empty(&hub_event_list)) {
			spin_unlock_irq(&hub_event_lock);
			break;
		}

		tmp = hub_event_list.next; //获取hub_event_list.next的指针,即当前hub
		list_del_init(tmp); //将当前hub从hub_event_list链表中删除

		hub = list_entry(tmp, struct usb_hub, event_list); //这里需要看下是如何将hub设备添加到链表中的???
		kref_get(&hub->kref);
		spin_unlock_irq(&hub_event_lock);

		hdev = hub->hdev; //从usb-hub中获取usb设备
		hub_dev = hub->intfdev; 
		intf = to_usb_interface(hub_dev); //获取接口
		dev_dbg(hub_dev, "state %d ports %d chg %04x evt %04x\n",
				hdev->state, hub->descriptor
					? hub->descriptor->bNbrPorts
					: 0,
				/* NOTE: expects max 15 ports... */
				(u16) hub->change_bits[0],
				(u16) hub->event_bits[0]);

		/* Lock the device, then check to see if we were
		 * disconnected while waiting for the lock to succeed. */
		usb_lock_device(hdev);
		if (unlikely(hub->disconnected))
			goto loop_disconnected;

		/* If the hub has died, clean up after it */
		if (hdev->state == USB_STATE_NOTATTACHED) { /*判定当前的hub是否没有被附上(断开)*/
			hub->error = -ENODEV;
			hub_quiesce(hub, HUB_DISCONNECT);
			goto loop;
		}

		/* Autoresume */
		ret = usb_autopm_get_interface(intf);
		if (ret) {
			dev_dbg(hub_dev, "Can't autoresume: %d\n", ret);
			goto loop;
		}

		/* If this is an inactive hub, do nothing */
		if (hub->quiescing) //quiescing:静默
			goto loop_autopm;

		if (hub->error) {
			dev_dbg (hub_dev, "resetting for error %d\n",
				hub->error);

			ret = usb_reset_device(hdev);
			if (ret) {
				dev_dbg (hub_dev,
					"error resetting hub: %d\n", ret);
				goto loop_autopm;
			}

			hub->nerrors = 0;
			hub->error = 0;
		}

		/* deal with port status changes */
		for (i = 1; i <= hub->descriptor->bNbrPorts; i++) { //遍历端口
			if (test_bit(i, hub->busy_bits))
				continue;
			connect_change = test_bit(i, hub->change_bits);
			wakeup_change = test_and_clear_bit(i, hub->wakeup_bits);
			if (!test_and_clear_bit(i, hub->event_bits) &&
					!connect_change && !wakeup_change)
				continue;

			ret = hub_port_status(hub, i,
					&portstatus, &portchange);
			if (ret < 0)
				continue;

			if (portchange & USB_PORT_STAT_C_CONNECTION) { //端口状态连接?
				usb_clear_port_feature(hdev, i,
					USB_PORT_FEAT_C_CONNECTION);
				connect_change = 1;
			}

			if (portchange & USB_PORT_STAT_C_ENABLE) { //端口状态使能?
				if (!connect_change)
					dev_dbg (hub_dev,
						"port %d enable change, "
						"status %08x\n",
						i, portstatus);
				usb_clear_port_feature(hdev, i,
					USB_PORT_FEAT_C_ENABLE);

				/*
				 * EM interference sometimes causes badly
				 * shielded USB devices to be shutdown by
				 * the hub, this hack enables them again.
				 * Works at least with mouse driver. 
				 */
				if (!(portstatus & USB_PORT_STAT_ENABLE)
				    && !connect_change
				    && hub->ports[i - 1]->child) {
					dev_err (hub_dev,
					    "port %i "
					    "disabled by hub (EMI?), "
					    "re-enabling...\n",
						i);
					connect_change = 1;
				}
			}

			//确定是否远程唤醒,如usb模块进入了休眠
			if (hub_handle_remote_wakeup(hub, i,
						portstatus, portchange))
				connect_change = 1;

			if (portchange & USB_PORT_STAT_C_OVERCURRENT) { //端口状态过流?
				u16 status = 0;
				u16 unused;

				dev_dbg(hub_dev, "over-current change on port "
					"%d\n", i);
				usb_clear_port_feature(hdev, i,
					USB_PORT_FEAT_C_OVER_CURRENT);
				msleep(100);	/* Cool down */
				hub_power_on(hub, true);
				hub_port_status(hub, i, &status, &unused);
				if (status & USB_PORT_STAT_OVERCURRENT)
					dev_err(hub_dev, "over-current "
						"condition on port %d\n", i);
			}

			if (portchange & USB_PORT_STAT_C_RESET) { //端口状态复位?
				dev_dbg (hub_dev,
					"reset change on port %d\n",
					i);
				usb_clear_port_feature(hdev, i,
					USB_PORT_FEAT_C_RESET);
			}
			if ((portchange & USB_PORT_STAT_C_BH_RESET) &&
					hub_is_superspeed(hub->hdev)) {
				dev_dbg(hub_dev,
					"warm reset change on port %d\n",
					i);
				usb_clear_port_feature(hdev, i,
					USB_PORT_FEAT_C_BH_PORT_RESET);
			}
			if (portchange & USB_PORT_STAT_C_LINK_STATE) {
				usb_clear_port_feature(hub->hdev, i,
						USB_PORT_FEAT_C_PORT_LINK_STATE);
			}
			if (portchange & USB_PORT_STAT_C_CONFIG_ERROR) {
				dev_warn(hub_dev,
					"config error on port %d\n",
					i);
				usb_clear_port_feature(hub->hdev, i,
						USB_PORT_FEAT_C_PORT_CONFIG_ERROR);
			}

			/* Warm reset a USB3 protocol port if it's in
			 * SS.Inactive state.
			 */
			if (hub_port_warm_reset_required(hub, portstatus)) {
				int status;
				struct usb_device *udev =
					hub->ports[i - 1]->child;

				dev_dbg(hub_dev, "warm reset port %d\n", i);
				if (!udev ||
				    !(portstatus & USB_PORT_STAT_CONNECTION) ||
				    udev->state == USB_STATE_NOTATTACHED) {
					status = hub_port_reset(hub, i,
							NULL, HUB_BH_RESET_TIME,
							true);
					if (status < 0)
						hub_port_disable(hub, i, 1);
				} else {
					usb_lock_device(udev);
					status = usb_reset_device(udev);
					usb_unlock_device(udev);
					connect_change = 0;
				}
			}

			if (connect_change) //从上面遍历的端口中获取到usb口有改变,将调用如下接口!!!
				hub_port_connect_change(hub, i,
						portstatus, portchange);
		} /* end for i */

		/* deal with hub status changes */
		if (test_and_clear_bit(0, hub->event_bits) == 0)
			;	/* do nothing */
		else if (hub_hub_status(hub, &hubstatus, &hubchange) < 0)
			dev_err (hub_dev, "get_hub_status failed\n");
		else {
			if (hubchange & HUB_CHANGE_LOCAL_POWER) {
				dev_dbg (hub_dev, "power change\n");
				clear_hub_feature(hdev, C_HUB_LOCAL_POWER);
				if (hubstatus & HUB_STATUS_LOCAL_POWER)
					/* FIXME: Is this always true? */
					hub->limited_power = 1;
				else
					hub->limited_power = 0;
			}
			if (hubchange & HUB_CHANGE_OVERCURRENT) {
				u16 status = 0;
				u16 unused;

				dev_dbg(hub_dev, "over-current change\n");
				clear_hub_feature(hdev, C_HUB_OVER_CURRENT);
				msleep(500);	/* Cool down */
                        	hub_power_on(hub, true);
				hub_hub_status(hub, &status, &unused);
				if (status & HUB_STATUS_OVERCURRENT)
					dev_err(hub_dev, "over-current "
						"condition\n");
			}
		}

 loop_autopm:
		/* Balance the usb_autopm_get_interface() above */
		usb_autopm_put_interface_no_suspend(intf);
 loop:
		/* Balance the usb_autopm_get_interface_no_resume() in
		 * kick_khubd() and allow autosuspend.
		 */
		usb_autopm_put_interface(intf);
 loop_disconnected:
		usb_unlock_device(hdev);
		kref_put(&hub->kref, hub_release);

        } /* end while (1) */
}

从hub_event_list链表中获取当前的hub,然后遍历该hub的端口,判断该端口对应的状态(状态包括:是否过流、端口是否使能、端口复位...)是否改变正确(正确connect_change=1,反之=0),正确将调用hub_port_connect_change()。

5. hub_port_connect_change()

static void hub_port_connect_change(struct usb_hub *hub, int port1,
					u16 portstatus, u16 portchange)
{
	struct usb_device *hdev = hub->hdev; //这个值在usb_hcd_poll_rh_status()函数内部有操作
	struct device *hub_dev = hub->intfdev;
	struct usb_hcd *hcd = bus_to_hcd(hdev->bus);
	unsigned wHubCharacteristics =
			le16_to_cpu(hub->descriptor->wHubCharacteristics);
	struct usb_device *udev;
	int status, i;
	unsigned unit_load;

	dev_dbg (hub_dev,
		"port %d, status %04x, change %04x, %s\n",
		port1, portstatus, portchange, portspeed(hub, portstatus));

	if (hub->has_indicators) { 
		set_port_led(hub, port1, HUB_LED_AUTO);
		hub->indicator[port1-1] = INDICATOR_AUTO;
	}

#ifdef	CONFIG_USB_OTG
	/* during HNP, don't repeat the debounce */
	if (hdev->bus->is_b_host)
		portchange &= ~(USB_PORT_STAT_C_CONNECTION |
				USB_PORT_STAT_C_ENABLE);
#endif

	/* Try to resuscitate an existing device */
	udev = hub->ports[port1 - 1]->child;
	if ((portstatus & USB_PORT_STAT_CONNECTION) && udev &&
			udev->state != USB_STATE_NOTATTACHED) {
		usb_lock_device(udev);
		if (portstatus & USB_PORT_STAT_ENABLE) {
			status = 0;		/* Nothing to do */

#ifdef CONFIG_PM_RUNTIME
		} else if (udev->state == USB_STATE_SUSPENDED &&
				udev->persist_enabled) {
			/* For a suspended device, treat this as a
			 * remote wakeup event.
			 */
			status = usb_remote_wakeup(udev);
#endif

		} else {
			status = -ENODEV;	/* Don't resuscitate */
		}
		usb_unlock_device(udev);

		if (status == 0) {
			clear_bit(port1, hub->change_bits);
			return;
		}
	}

	/* Disconnect any existing devices under this port */
	if (udev) {
		if (hcd->phy && !hdev->parent &&
				!(portstatus & USB_PORT_STAT_CONNECTION))
			usb_phy_notify_disconnect(hcd->phy, udev->speed);
		usb_disconnect(&hub->ports[port1 - 1]->child);
	}
	clear_bit(port1, hub->change_bits);

	/* We can forget about a "removed" device when there's a physical
	 * disconnect or the connect status changes.
	 */
	if (!(portstatus & USB_PORT_STAT_CONNECTION) || //端口状态为链接
			(portchange & USB_PORT_STAT_C_CONNECTION)) //端口改变为链接
		clear_bit(port1, hub->removed_bits);

	if (portchange & (USB_PORT_STAT_C_CONNECTION |
				USB_PORT_STAT_C_ENABLE)) {
		status = hub_port_debounce_be_stable(hub, port1); //防抖处理
		if (status < 0) {
			if (status != -ENODEV && printk_ratelimit())
				dev_err(hub_dev, "connect-debounce failed, "
						"port %d disabled\n", port1);
			portstatus &= ~USB_PORT_STAT_CONNECTION;
		} else {
			portstatus = status;
		}
	}

	/* Return now if debouncing failed or nothing is connected or
	 * the device was "removed".
	 */
	if (!(portstatus & USB_PORT_STAT_CONNECTION) ||
			test_bit(port1, hub->removed_bits)) {

		/* maybe switch power back on (e.g. root hub was reset) */
		if ((wHubCharacteristics & HUB_CHAR_LPSM) < 2
				&& !port_is_power_on(hub, portstatus))
			set_port_feature(hdev, port1, USB_PORT_FEAT_POWER);

		if (portstatus & USB_PORT_STAT_ENABLE)
  			goto done;
		return;
	}
	if (hub_is_superspeed(hub->hdev))
		unit_load = 150;
	else
		unit_load = 100;

	status = 0;
	for (i = 0; i < SET_CONFIG_TRIES; i++) {

		/* reallocate for each attempt, since references
		 * to the previous one can escape in various ways
		 */
		udev = usb_alloc_dev(hdev, hdev->bus, port1); //分配一个usb设备
		if (!udev) {
			dev_err (hub_dev,
				"couldn't allocate port %d usb_device\n",
				port1);
			goto done;
		}

		usb_set_device_state(udev, USB_STATE_POWERED);
 		udev->bus_mA = hub->mA_per_port;
		udev->level = hdev->level + 1;
		udev->wusb = hub_is_wusb(hub);

		/* Only USB 3.0 devices are connected to SuperSpeed hubs. */
		if (hub_is_superspeed(hub->hdev))
			udev->speed = USB_SPEED_SUPER;
		else
			udev->speed = USB_SPEED_UNKNOWN;

		choose_devnum(udev); //选择一个usb设备编号
		if (udev->devnum <= 0) {
			status = -ENOTCONN;	/* Don't retry */
			goto loop;
		}

		/* reset (non-USB 3.0 devices) and get descriptor */
		status = hub_port_init(hub, udev, port1, i);
		if (status < 0)
			goto loop;

		usb_detect_quirks(udev);
		if (udev->quirks & USB_QUIRK_DELAY_INIT)
			msleep(1000);

		/* consecutive bus-powered hubs aren't reliable; they can
		 * violate the voltage drop budget.  if the new child has
		 * a "powered" LED, users should notice we didn't enable it
		 * (without reading syslog), even without per-port LEDs
		 * on the parent.
		 */
		if (udev->descriptor.bDeviceClass == USB_CLASS_HUB
				&& udev->bus_mA <= unit_load) {
			u16	devstat;

			status = usb_get_status(udev, USB_RECIP_DEVICE, 0,
					&devstat);
			if (status < 2) {
				dev_dbg(&udev->dev, "get status %d ?\n", status);
				goto loop_disable;
			}
			le16_to_cpus(&devstat);
			if ((devstat & (1 << USB_DEVICE_SELF_POWERED)) == 0) {
				dev_err(&udev->dev,
					"can't connect bus-powered hub "
					"to this port\n");
				if (hub->has_indicators) {
					hub->indicator[port1-1] =
						INDICATOR_AMBER_BLINK;
					schedule_delayed_work (&hub->leds, 0);
				}
				status = -ENOTCONN;	/* Don't retry */
				goto loop_disable;
			}
		}
 
		/* check for devices running slower than they could */
		if (le16_to_cpu(udev->descriptor.bcdUSB) >= 0x0200
				&& udev->speed == USB_SPEED_FULL
				&& highspeed_hubs != 0)
			check_highspeed (hub, udev, port1);

		/* Store the parent's children[] pointer.  At this point
		 * udev becomes globally accessible, although presumably
		 * no one will look at it until hdev is unlocked.
		 */
		status = 0;

		/* We mustn't add new devices if the parent hub has
		 * been disconnected; we would race with the
		 * recursively_mark_NOTATTACHED() routine.
		 */
		spin_lock_irq(&device_state_lock);
		if (hdev->state == USB_STATE_NOTATTACHED)
			status = -ENOTCONN;
		else
			hub->ports[port1 - 1]->child = udev;
		spin_unlock_irq(&device_state_lock);

		/* Run it through the hoops (find a driver, etc) */
		if (!status) {
			status = usb_new_device(udev); //新建一个usb设备
			if (status) {
				spin_lock_irq(&device_state_lock);
				hub->ports[port1 - 1]->child = NULL;
				spin_unlock_irq(&device_state_lock);
			}
		}

		if (status)
			goto loop_disable;

		status = hub_power_remaining(hub);
		if (status)
			dev_dbg(hub_dev, "%dmA power budget left\n", status);

		return;

loop_disable:
		hub_port_disable(hub, port1, 1);
loop:
		usb_ep0_reinit(udev);
		release_devnum(udev);
		hub_free_dev(udev);
		usb_put_dev(udev);
		if ((status == -ENOTCONN) || (status == -ENOTSUPP))
			break;
	}
	if (hub->hdev->parent ||
			!hcd->driver->port_handed_over ||
			!(hcd->driver->port_handed_over)(hcd, port1)) {
		if (status != -ENOTCONN && status != -ENODEV)
			dev_err(hub_dev, "unable to enumerate USB device on port %d\n",
					port1);
	}
 
done:
	hub_port_disable(hub, port1, 1);
	if (hcd->driver->relinquish_port && !hub->hdev->parent)
		hcd->driver->relinquish_port(hcd, port1);
}

该函数通过对端口状态的改变进行端口连接状态的判定(包括是否重新复位端口、对端口防抖处理...),最后通过分配一个usb设备usb_alloc_dev()、选择设备编号choose_devnum(udev), hub_port_init()端口初始化、usb_new_device()新建一个usb设备。

5.1 usb_alloc_dev()

struct usb_device *usb_alloc_dev(struct usb_device *parent,
				 struct usb_bus *bus, unsigned port1)
{
	struct usb_device *dev;
	struct usb_hcd *usb_hcd = bus_to_hcd(bus);
	unsigned root_hub = 0;

	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (!dev)
		return NULL;

	if (!usb_get_hcd(usb_hcd)) {
		kfree(dev);
		return NULL;
	}
	/* Root hubs aren't true devices, so don't allocate HCD resources */
	if (usb_hcd->driver->alloc_dev && parent &&
		!usb_hcd->driver->alloc_dev(usb_hcd, dev)) {
		usb_put_hcd(bus_to_hcd(bus));
		kfree(dev);
		return NULL;
	}

	device_initialize(&dev->dev);
	dev->dev.bus = &usb_bus_type; //绑定设备的总线为“usb”
	dev->dev.type = &usb_device_type; //设备的类型
	dev->dev.groups = usb_device_groups;
	dev->dev.dma_mask = bus->controller->dma_mask;
	set_dev_node(&dev->dev, dev_to_node(bus->controller));
	dev->state = USB_STATE_ATTACHED; //设置usb状态为绑定
	dev->lpm_disable_count = 1;
	atomic_set(&dev->urbnum, 0);

	INIT_LIST_HEAD(&dev->ep0.urb_list);
	dev->ep0.desc.bLength = USB_DT_ENDPOINT_SIZE; //设置断点长度
	dev->ep0.desc.bDescriptorType = USB_DT_ENDPOINT; //设置端点描述符
	/* ep0 maxpacket comes later, from device descriptor */
	usb_enable_endpoint(dev, &dev->ep0, false);
	dev->can_submit = 1;

	/* Save readable and stable topology id, distinguishing devices
	 * by location for diagnostics, tools, driver model, etc.  The
	 * string is a path along hub ports, from the root.  Each device's
	 * dev->devpath will be stable until USB is re-cabled, and hubs
	 * are often labeled with these port numbers.  The name isn't
	 * as stable:  bus->busnum changes easily from modprobe order,
	 * cardbus or pci hotplugging, and so on.
	 */
	if (unlikely(!parent)) {
		dev->devpath[0] = '0';
		dev->route = 0;

		dev->dev.parent = bus->controller;
		dev_set_name(&dev->dev, "usb%d", bus->busnum);
		root_hub = 1;
	} else {
		/* match any labeling on the hubs; it's one-based */
		if (parent->devpath[0] == '0') {
			snprintf(dev->devpath, sizeof dev->devpath,
				"%d", port1);
			/* Root ports are not counted in route string */
			dev->route = 0;
		} else {
			snprintf(dev->devpath, sizeof dev->devpath,
				"%s.%d", parent->devpath, port1);
			/* Route string assumes hubs have less than 16 ports */
			if (port1 < 15)
				dev->route = parent->route +
					(port1 << ((parent->level - 1)*4));
			else
				dev->route = parent->route +
					(15 << ((parent->level - 1)*4));
		}

		dev->dev.parent = &parent->dev;
		dev_set_name(&dev->dev, "%d-%s", bus->busnum, dev->devpath);

		/* hub driver sets up TT records */
	}

	dev->portnum = port1;
	dev->bus = bus;
	dev->parent = parent;
	INIT_LIST_HEAD(&dev->filelist);

#ifdef	CONFIG_PM
	pm_runtime_set_autosuspend_delay(&dev->dev,
			usb_autosuspend_delay * 1000);
	dev->connect_time = jiffies;
	dev->active_duration = -jiffies;
#endif
	if (root_hub)	/* Root hub always ok [and always wired] */
		dev->authorized = 1;
	else {
		dev->authorized = usb_hcd->authorized_default;
		dev->wusb = usb_bus_is_wusb(bus)? 1 : 0;
	}
	return dev;
}

分配一个usb设备,包括绑定总线类型为usb,设备的类型为设备(非接口),设置端点0的描述符长度、类型,最后设置该设备的名称:dev_set_name(&dev->dev, "%d-%s", bus->busnum, dev->devpath)。

5.2 choose_devnum()

static void choose_devnum(struct usb_device *udev)
{
	int		devnum;
	struct usb_bus	*bus = udev->bus;

	/* If khubd ever becomes multithreaded, this will need a lock */
	if (udev->wusb) {
		devnum = udev->portnum + 1;
		BUG_ON(test_bit(devnum, bus->devmap.devicemap));
	} else {
		/* Try to allocate the next devnum beginning at
		 * bus->devnum_next. */
		devnum = find_next_zero_bit(bus->devmap.devicemap, 128,
					    bus->devnum_next);
		if (devnum >= 128)
			devnum = find_next_zero_bit(bus->devmap.devicemap,
						    128, 1);
		bus->devnum_next = ( devnum >= 127 ? 1 : devnum + 1);
	}
	if (devnum < 128) {
		set_bit(devnum, bus->devmap.devicemap);
		udev->devnum = devnum;
	}
}

从bus->devmap.devicemap中分配一个未被占用的bit位作为当前分配的设备编号。

5.3 hub_port_init()

static int
hub_port_init (struct usb_hub *hub, struct usb_device *udev, int port1,
		int retry_counter)
{
	static DEFINE_MUTEX(usb_address0_mutex);

	struct usb_device	*hdev = hub->hdev;
	struct usb_hcd		*hcd = bus_to_hcd(hdev->bus);
	int			i, j, retval;
	unsigned		delay = HUB_SHORT_RESET_TIME;
	enum usb_device_speed	oldspeed = udev->speed;
	const char		*speed;
	int			devnum = udev->devnum;

	/* root hub ports have a slightly longer reset period
	 * (from USB 2.0 spec, section 7.1.7.5)
	 */
	if (!hdev->parent) {
		delay = HUB_ROOT_RESET_TIME;
		if (port1 == hdev->bus->otg_port)
			hdev->bus->b_hnp_enable = 0;
	}

	/* Some low speed devices have problems with the quick delay, so */
	/*  be a bit pessimistic with those devices. RHbug #23670 */
	if (oldspeed == USB_SPEED_LOW)
		delay = HUB_LONG_RESET_TIME;

	mutex_lock(&usb_address0_mutex);

	/* Reset the device; full speed may morph to high speed */
	/* FIXME a USB 2.0 device may morph into SuperSpeed on reset. */
	retval = hub_port_reset(hub, port1, udev, delay, false); //复位设备
	if (retval < 0)		/* error or disconnect */
		goto fail;
	/* success, speed is known */

	retval = -ENODEV;

	if (oldspeed != USB_SPEED_UNKNOWN && oldspeed != udev->speed) {
		dev_dbg(&udev->dev, "device reset changed speed!\n");
		goto fail;
	}
	oldspeed = udev->speed;

	/* USB 2.0 section 5.5.3 talks about ep0 maxpacket ...
	 * it's fixed size except for full speed devices.
	 * For Wireless USB devices, ep0 max packet is always 512 (tho
	 * reported as 0xff in the device descriptor). WUSB1.0[4.8.1].
	 */

	//先根据不同的速率,初始化传输包的字节数
	switch (udev->speed) {
	case USB_SPEED_SUPER:
	case USB_SPEED_WIRELESS:	/* fixed at 512 */
		udev->ep0.desc.wMaxPacketSize = cpu_to_le16(512);
		break;
	case USB_SPEED_HIGH:		/* fixed at 64 */
		udev->ep0.desc.wMaxPacketSize = cpu_to_le16(64);
		break;
	case USB_SPEED_FULL:		/* 8, 16, 32, or 64 */
		/* to determine the ep0 maxpacket size, try to read
		 * the device descriptor to get bMaxPacketSize0 and
		 * then correct our initial guess.
		 */
		udev->ep0.desc.wMaxPacketSize = cpu_to_le16(64);
		break;
	case USB_SPEED_LOW:		/* fixed at 8 */
		udev->ep0.desc.wMaxPacketSize = cpu_to_le16(8);
		break;
	default:
		goto fail;
	}

	if (udev->speed == USB_SPEED_WIRELESS)
		speed = "variable speed Wireless";
	else
		speed = usb_speed_string(udev->speed);

	if (udev->speed != USB_SPEED_SUPER)
		dev_info(&udev->dev,
				"%s %s USB device number %d using %s\n",
				(udev->config) ? "reset" : "new", speed,
				devnum, udev->bus->controller->driver->name);

	/* Set up TT records, if needed  */
	//usb2.0与usb1.0、usb1.1转换
	if (hdev->tt) { 
		udev->tt = hdev->tt;
		udev->ttport = hdev->ttport;
	} else if (udev->speed != USB_SPEED_HIGH
			&& hdev->speed == USB_SPEED_HIGH) {
		if (!hub->tt.hub) {
			dev_err(&udev->dev, "parent hub has no TT\n");
			retval = -EINVAL;
			goto fail;
		}
		udev->tt = &hub->tt;
		udev->ttport = port1;
	}
 
	/* Why interleave GET_DESCRIPTOR and SET_ADDRESS this way?
	 * Because device hardware and firmware is sometimes buggy in
	 * this area, and this is how Linux has done it for ages.
	 * Change it cautiously.
	 *
	 * NOTE:  If USE_NEW_SCHEME() is true we will start by issuing
	 * a 64-byte GET_DESCRIPTOR request.  This is what Windows does,
	 * so it may help with some non-standards-compliant devices.
	 * Otherwise we start with SET_ADDRESS and then try to read the
	 * first 8 bytes of the device descriptor to get the ep0 maxpacket
	 * value.
	 */

	//		
	for (i = 0; i < GET_DESCRIPTOR_TRIES; (++i, msleep(100))) {
		if (USE_NEW_SCHEME(retry_counter) && !(hcd->driver->flags & HCD_USB3)) {
			struct usb_device_descriptor *buf;
			int r = 0;

#define GET_DESCRIPTOR_BUFSIZE	64
			buf = kmalloc(GET_DESCRIPTOR_BUFSIZE, GFP_NOIO);
			if (!buf) {
				retval = -ENOMEM;
				continue;
			}

			/* Retry on all errors; some devices are flakey.
			 * 255 is for WUSB devices, we actually need to use
			 * 512 (WUSB1.0[4.8.1]).
			 */
			for (j = 0; j < 3; ++j) {
				buf->bMaxPacketSize0 = 0;
				r = usb_control_msg(udev, usb_rcvaddr0pipe(), //获取64字节的设备描述符
					USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
					USB_DT_DEVICE << 8, 0,
					buf, GET_DESCRIPTOR_BUFSIZE,
					initial_descriptor_timeout);
				switch (buf->bMaxPacketSize0) {
				case 8: case 16: case 32: case 64: case 255:
					if (buf->bDescriptorType ==
							USB_DT_DEVICE) {
						r = 0;
						break;
					}
					/* FALL THROUGH */
				default:
					if (r == 0)
						r = -EPROTO;
					break;
				}
				if (r == 0)
					break;
			}
			udev->descriptor.bMaxPacketSize0 =
					buf->bMaxPacketSize0; //以当前获取到的设备描述符传输包的长度赋值
			kfree(buf);

			retval = hub_port_reset(hub, port1, udev, delay, false); //复位设备
			if (retval < 0)		/* error or disconnect */
				goto fail;
			if (oldspeed != udev->speed) {
				dev_dbg(&udev->dev,
					"device reset changed speed!\n");
				retval = -ENODEV;
				goto fail;
			}
			if (r) {
				if (r != -ENODEV)
					dev_err(&udev->dev, "device descriptor read/64, error %d\n",
							r);
				retval = -EMSGSIZE;
				continue;
			}
#undef GET_DESCRIPTOR_BUFSIZE
		}

 		/*
 		 * If device is WUSB, we already assigned an
 		 * unauthorized address in the Connect Ack sequence;
 		 * authorization will assign the final address.
 		 */
		if (udev->wusb == 0) {
			for (j = 0; j < SET_ADDRESS_TRIES; ++j) {
				retval = hub_set_address(udev, devnum); //设置设备的地址为devnum
				if (retval >= 0)
					break;
				msleep(200);
			}
			if (retval < 0) {
				if (retval != -ENODEV)
					dev_err(&udev->dev, "device not accepting address %d, error %d\n",
							devnum, retval);
				goto fail;
			}
			if (udev->speed == USB_SPEED_SUPER) {
				devnum = udev->devnum;
				dev_info(&udev->dev,
						"%s SuperSpeed USB device number %d using %s\n",
						(udev->config) ? "reset" : "new",
						devnum, udev->bus->controller->driver->name);
			}

			/* cope with hardware quirkiness:
			 *  - let SET_ADDRESS settle, some device hardware wants it
			 *  - read ep0 maxpacket even for high and low speed,
			 */
			msleep(10);
			if (USE_NEW_SCHEME(retry_counter) && !(hcd->driver->flags & HCD_USB3))
				break;
  		}

		retval = usb_get_device_descriptor(udev, 8); //获取长度为8个字节的设备描述,这是因为第8个字节的偏移为bMaxPacketSize0,而下面需要!!
		if (retval < 8) {
			if (retval != -ENODEV)
				dev_err(&udev->dev,
					"device descriptor read/8, error %d\n",
					retval);
			if (retval >= 0)
				retval = -EMSGSIZE;
		} else {
			retval = 0;
			break;
		}
	}
	if (retval)
		goto fail;

	if (hcd->phy && !hdev->parent)
		usb_phy_notify_connect(hcd->phy, udev->speed);

	/*
	 * Some superspeed devices have finished the link training process
	 * and attached to a superspeed hub port, but the device descriptor
	 * got from those devices show they aren't superspeed devices. Warm
	 * reset the port attached by the devices can fix them.
	 */
	if ((udev->speed == USB_SPEED_SUPER) &&
			(le16_to_cpu(udev->descriptor.bcdUSB) < 0x0300)) {
		dev_err(&udev->dev, "got a wrong device descriptor, "
				"warm reset device\n");
		hub_port_reset(hub, port1, udev,
				HUB_BH_RESET_TIME, true);
		retval = -EINVAL;
		goto fail;
	}

	if (udev->descriptor.bMaxPacketSize0 == 0xff ||
			udev->speed == USB_SPEED_SUPER)
		i = 512;
	else
		i = udev->descriptor.bMaxPacketSize0;
	if (usb_endpoint_maxp(&udev->ep0.desc) != i) {
		if (udev->speed == USB_SPEED_LOW ||
				!(i == 8 || i == 16 || i == 32 || i == 64)) {
			dev_err(&udev->dev, "Invalid ep0 maxpacket: %d\n", i);
			retval = -EMSGSIZE;
			goto fail;
		}
		if (udev->speed == USB_SPEED_FULL)
			dev_dbg(&udev->dev, "ep0 maxpacket = %d\n", i);
		else
			dev_warn(&udev->dev, "Using ep0 maxpacket: %d\n", i);
		udev->ep0.desc.wMaxPacketSize = cpu_to_le16(i);
		usb_ep0_reinit(udev);
	}
  
	retval = usb_get_device_descriptor(udev, USB_DT_DEVICE_SIZE); //再次获取USB_DT_DEVICE_SIZE设备描述符的字节数
	if (retval < (signed)sizeof(udev->descriptor)) {
		if (retval != -ENODEV)
			dev_err(&udev->dev, "device descriptor read/all, error %d\n",
					retval);
		if (retval >= 0)
			retval = -ENOMSG;
		goto fail;
	}

	if (udev->wusb == 0 && le16_to_cpu(udev->descriptor.bcdUSB) >= 0x0201) {
		retval = usb_get_bos_descriptor(udev);
		if (!retval) {
			udev->lpm_capable = usb_device_supports_lpm(udev);
			usb_set_lpm_parameters(udev);
		}
	}

	retval = 0;
	/* notify HCD that we have a device connected and addressed */
	if (hcd->driver->update_device)
		hcd->driver->update_device(hcd, udev);
fail:
	if (retval) {
		hub_port_disable(hub, port1, 0);
		update_devnum(udev, devnum);	/* for disconnect processing */
	}
	mutex_unlock(&usb_address0_mutex);
	return retval;
}
该函数主要的功能是:复位设备、分配地址、获取分配地址对应设备的描述符。

5. 4 usb_new_device() 设备枚举

int usb_new_device(struct usb_device *udev)
{
	int err;

	if (udev->parent) {
		/* Initialize non-root-hub device wakeup to disabled;
		 * device (un)configuration controls wakeup capable
		 * sysfs power/wakeup controls wakeup enabled/disabled
		 */
		device_init_wakeup(&udev->dev, 0);
	}

	/* Tell the runtime-PM framework the device is active */
	pm_runtime_set_active(&udev->dev);
	pm_runtime_get_noresume(&udev->dev);
	pm_runtime_use_autosuspend(&udev->dev);
	pm_runtime_enable(&udev->dev);

	/* By default, forbid autosuspend for all devices.  It will be
	 * allowed for hubs during binding.
	 */
	usb_disable_autosuspend(udev);

	//枚举设备
	err = usb_enumerate_device(udev);	/* Read descriptors */
	if (err < 0)
		goto fail;
	dev_dbg(&udev->dev, "udev %d, busnum %d, minor = %d\n",
			udev->devnum, udev->bus->busnum,
			(((udev->bus->busnum-1) * 128) + (udev->devnum-1)));
	/* export the usbdev device-node for libusb */
	udev->dev.devt = MKDEV(USB_DEVICE_MAJOR,
			(((udev->bus->busnum-1) * 128) + (udev->devnum-1)));

	/* Tell the world! */
	announce_device(udev);

	if (udev->serial)
		add_device_randomness(udev->serial, strlen(udev->serial));
	if (udev->product)
		add_device_randomness(udev->product, strlen(udev->product));
	if (udev->manufacturer)
		add_device_randomness(udev->manufacturer,
				      strlen(udev->manufacturer));

	device_enable_async_suspend(&udev->dev);

	/*
	 * check whether the hub marks this port as non-removable. Do it
	 * now so that platform-specific data can override it in
	 * device_add()
	 */
	if (udev->parent)
		set_usb_port_removable(udev);

	/* Register the device.  The device driver is responsible
	 * for configuring the device and invoking the add-device
	 * notifier chain (used by usbfs and possibly others).
	 */
	err = device_add(&udev->dev);
	if (err) {
		dev_err(&udev->dev, "can't device_add, error %d\n", err);
		goto fail;
	}

	/* Create link files between child device and usb port device. */
	if (udev->parent) {
		struct usb_hub *hub = usb_hub_to_struct_hub(udev->parent);
		struct usb_port	*port_dev = hub->ports[udev->portnum - 1];

		err = sysfs_create_link(&udev->dev.kobj,
				&port_dev->dev.kobj, "port");
		if (err)
			goto fail;

		err = sysfs_create_link(&port_dev->dev.kobj,
				&udev->dev.kobj, "device");
		if (err) {
			sysfs_remove_link(&udev->dev.kobj, "port");
			goto fail;
		}

		pm_runtime_get_sync(&port_dev->dev);
	}

	(void) usb_create_ep_devs(&udev->dev, &udev->ep0, udev);
	usb_mark_last_busy(udev);
	pm_runtime_put_sync_autosuspend(&udev->dev);
	return err;

fail:
	usb_set_device_state(udev, USB_STATE_NOTATTACHED);
	pm_runtime_disable(&udev->dev);
	pm_runtime_set_suspended(&udev->dev);
	return err;
}

该函数主要是通过usb_enumerate_device(udev)完成“设备枚举”(设备枚举的具体细节已经分析过,详见:点击打开链接, 5.6 小节),最后通过device_add(&udev->dev)将设备通添加到usb总线上,同时匹配对应的驱动,接下来将详细分析!!!

5.4.1 device_add()

int device_add(struct device *dev)
{
	struct device *parent = NULL;
	struct kobject *kobj;
	struct class_interface *class_intf;
	int error = -EINVAL;

	dev = get_device(dev);
	if (!dev)
		goto done;

	if (!dev->p) {
		error = device_private_init(dev);
		if (error)
			goto done;
	}

	/*
	 * for statically allocated devices, which should all be converted
	 * some day, we need to initialize the name. We prevent reading back
	 * the name, and force the use of dev_name()
	 */
	if (dev->init_name) {
		dev_set_name(dev, "%s", dev->init_name); //dev->init_name = "platform"
		dev->init_name = NULL;
	}

	/* subsystems can specify simple device enumeration */
	if (!dev_name(dev) && dev->bus && dev->bus->dev_name)
		dev_set_name(dev, "%s%u", dev->bus->dev_name, dev->id);

	if (!dev_name(dev)) {
		error = -EINVAL;
		goto name_error;
	}

	pr_debug("device: '%s': %s\n", dev_name(dev), __func__);

	parent = get_device(dev->parent); //dev->parent=platform_bus结构体
	kobj = get_device_parent(dev, parent);
	if (kobj)
		dev->kobj.parent = kobj;

	/* use parent numa_node */
	if (parent)
		set_dev_node(dev, dev_to_node(parent));

	/* first, register with generic layer. */
	/* we require the name to be set before, and pass NULL */
	error = kobject_add(&dev->kobj, dev->kobj.parent, NULL); //对象增加,其实就是在文件系统/sys/device/platform下新建文件pinctrl
	if (error)
		goto Error;

	/* notify platform of device entry */
	if (platform_notify)
		platform_notify(dev);

	error = device_create_file(dev, &uevent_attr);
	if (error)
		goto attrError;

	if (MAJOR(dev->devt)) {
		error = device_create_file(dev, &devt_attr);
		if (error)
			goto ueventattrError;

		error = device_create_sys_dev_entry(dev);
		if (error)
			goto devtattrError;

		devtmpfs_create_node(dev);
	}

	error = device_add_class_symlinks(dev);
	if (error)
		goto SymlinkError;
	error = device_add_attrs(dev); 
	if (error)
		goto AttrsError;
	error = bus_add_device(dev); //增加设备到总线上,是理解设备和驱动匹配的关键因素之一!
	if (error)
		goto BusError;
	error = dpm_sysfs_add(dev);
	if (error)
		goto DPMError;
	device_pm_add(dev);

	/* Notify clients of device addition.  This call must come
	 * after dpm_sysfs_add() and before kobject_uevent().
	 */
	if (dev->bus)
		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
					     BUS_NOTIFY_ADD_DEVICE, dev);

	kobject_uevent(&dev->kobj, KOBJ_ADD); //kobject内核用户层事件增加
	bus_probe_device(dev); //
	if (parent)
		klist_add_tail(&dev->p->knode_parent,
			       &parent->p->klist_children);

	if (dev->class) {
		mutex_lock(&dev->class->p->mutex);
		/* tie the class to the device */
		klist_add_tail(&dev->knode_class,
			       &dev->class->p->klist_devices);

		/* notify any interfaces that the device is here */
		list_for_each_entry(class_intf,
				    &dev->class->p->interfaces, node)
			if (class_intf->add_dev)
				class_intf->add_dev(dev, class_intf);
		mutex_unlock(&dev->class->p->mutex);
	}
done:
	put_device(dev);
	return error;
 DPMError:
	bus_remove_device(dev);
 BusError:
	device_remove_attrs(dev);
 AttrsError:
	device_remove_class_symlinks(dev);
 SymlinkError:
	if (MAJOR(dev->devt))
		devtmpfs_delete_node(dev);
	if (MAJOR(dev->devt))
		device_remove_sys_dev_entry(dev);
 devtattrError:
	if (MAJOR(dev->devt))
		device_remove_file(dev, &devt_attr);
 ueventattrError:
	device_remove_file(dev, &uevent_attr);
 attrError:
	kobject_uevent(&dev->kobj, KOBJ_REMOVE);
	kobject_del(&dev->kobj);
 Error:
	cleanup_device_parent(dev);
	if (parent)
		put_device(parent);
name_error:
	kfree(dev->p);
	dev->p = NULL;
	goto done;
}

该函数内部知识点较多,包括内核对象添加kobject_add()、sys文件系统属性绑定device_create_file()、将当前设备添加到usb总线的设备链表中bus_add_device()、最后通过bus_probe_device()匹配对应的驱动,这里将重点分析!

void bus_probe_device(struct device *dev)
{
	struct bus_type *bus = dev->bus;
	struct subsys_interface *sif;
	int ret;

	if (!bus)
		return;

	if (bus->p->drivers_autoprobe) { //在USB总线注册时,drivers_autoprobe已初始化为1
		ret = device_attach(dev); //设备绑定,见下面分析
		WARN_ON(ret < 0);
	}

	mutex_lock(&bus->p->mutex);
	list_for_each_entry(sif, &bus->p->interfaces, node)
		if (sif->add_dev)
			sif->add_dev(dev, sif);
	mutex_unlock(&bus->p->mutex);
}
int device_attach(struct device *dev)
{
	int ret = 0;

	device_lock(dev);

	//由于设备和驱动有对应的关系,一个设备只能对应一个驱动,而一个驱动可以对应
	//多个设备,所以dev->driver为真就表示当前设备已经绑定了对应的驱动,否则就要
	//遍历驱动链表寻找匹配的
	if (dev->driver) {
		if (klist_node_attached(&dev->p->knode_driver)) {
			ret = 1;
			goto out_unlock;
		}
		ret = device_bind_driver(dev); //确定是否绑定对应的驱动
		if (ret == 0)
			ret = 1;
		else {
			dev->driver = NULL;
			ret = 0;
		}
	} else {
		ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
		pm_request_idle(dev);
	}
out_unlock:
	device_unlock(dev);
	return ret;
}
EXPORT_SYMBOL_GPL(device_attach);

      由于设备和驱动有对应的关系,一个设备只能对应一个驱动,而一个驱动可以对应多个设备,所以dev->driver为真就表示当前设备已经绑定了对应的驱动,否则就要遍历驱动链表寻找匹配的,我们这里时第一次执行,所以条件不成立,要匹配新的驱动。

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 *))
{
	struct klist_iter i;
	struct device_driver *drv;
	int error = 0;

	if (!bus)
		return -EINVAL;

	klist_iter_init_node(&bus->p->klist_drivers, &i,
			     start ? &start->p->knode_bus : NULL); //遍历usb总线上的驱动链表进行匹配
	while ((drv = next_driver(&i)) && !error)
		error = fn(drv, data);
	klist_iter_exit(&i);
	return error;
}
EXPORT_SYMBOL_GPL(bus_for_each_drv);

该函数内部将遍历usb总线上的驱动链表,将当前设备与驱动进行匹配,这里调用回调函数__device_attach(),详见如下:

static int __device_attach(struct device_driver *drv, void *data)
{
	struct device *dev = data;

	if (!driver_match_device(drv, dev)) //驱动和设备匹配判定
		return 0;

	return driver_probe_device(drv, dev); //调用usb总线上的探测函数
}
static inline int driver_match_device(struct device_driver *drv, struct device *dev)
{
	return drv->bus->match ? drv->bus->match(dev, drv) : 1;
}

这里的match函数将调用usb总线上的usb_device_match匹配函数,drv->bus->match=usb_bus_type.usb_device_match:

struct bus_type usb_bus_type = {
	.name =		"usb",
	.match =	usb_device_match, //将被调用
	.uevent =	usb_uevent,
};
static int usb_device_match(struct device *dev, struct device_driver *drv)
{
	/* devices and interfaces are handled separately */
	if (is_usb_device(dev)) { //是否是usb设备

		/* interface drivers never match devices */
		if (!is_usb_device_driver(drv))
			return 0;

		/* TODO: Add real matching code */
		return 1;

	} else if (is_usb_interface(dev)) { //是否是usb接口
		struct usb_interface *intf;
		struct usb_driver *usb_drv;
		const struct usb_device_id *id;

		/* device drivers never match interfaces */
		if (is_usb_device_driver(drv))
			return 0;

		intf = to_usb_interface(dev);
		usb_drv = to_usb_driver(drv);

		id = usb_match_id(intf, usb_drv->id_table);
		if (id)
			return 1;

		id = usb_match_dynamic_id(intf, usb_drv);
		if (id)
			return 1;
	}

	return 0;
}

在该函数内部我们这里匹配的时设备,所以执行if语句,在else语句内部是接口设备,我们知道,在usb驱动里真正与外设设备对应的时驱动而不是设备...现在在回到__device_attach函数内部的driver_probe_device()

int driver_probe_device(struct device_driver *drv, struct device *dev)
{
	int ret = 0;

	if (!device_is_registered(dev)) //判定当前设备是否已经注册过
		return -ENODEV;

	pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
		 drv->bus->name, __func__, dev_name(dev), drv->name);

	pm_runtime_barrier(dev);
	ret = really_probe(dev, drv); //调用真实的probe探测函数
	pm_request_idle(dev);

	return ret;
}
static int really_probe(struct device *dev, struct device_driver *drv)
{
	int ret = 0;

	atomic_inc(&probe_count);
	pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
		 drv->bus->name, __func__, drv->name, dev_name(dev));
	WARN_ON(!list_empty(&dev->devres_head));

	dev->driver = drv;

	/* If using pinctrl, bind pins now before probing */
	ret = pinctrl_bind_pins(dev); //待分析
	if (ret)
		goto probe_failed;

	if (driver_sysfs_add(dev)) {
		printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
			__func__, dev_name(dev));
		goto probe_failed;
	}

	if (dev->bus->probe) { //通过usb_driver_register(...)函数知道该条件不成立
		ret = dev->bus->probe(dev); 
		if (ret)
			goto probe_failed;
	} else if (drv->probe) { //终于找到你了,哈哈哈!!!
		ret = drv->probe(dev); //这里的probe函数就是usb驱动通用probe函数generic_probe
		if (ret)
			goto probe_failed;
	}

	driver_bound(dev);
	ret = 1;
	pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
		 drv->bus->name, __func__, dev_name(dev), drv->name);
	goto done;

probe_failed:
	devres_release_all(dev);
	driver_sysfs_remove(dev);
	dev->driver = NULL;
	dev_set_drvdata(dev, NULL);

	if (ret == -EPROBE_DEFER) {
		/* Driver requested deferred probing */
		dev_info(dev, "Driver %s requests probe deferral\n", drv->name);
		driver_deferred_probe_add(dev);
	} else if (ret != -ENODEV && ret != -ENXIO) {
		/* driver matched but the probe failed */
		printk(KERN_WARNING
		       "%s: probe of %s failed with error %d\n",
		       drv->name, dev_name(dev), ret);
	} else {
		pr_debug("%s: probe of %s rejects match %d\n",
		       drv->name, dev_name(dev), ret);
	}
	/*
	 * Ignore errors returned by ->probe so that the next driver can try
	 * its luck.
	 */
	ret = 0;
done:
	atomic_dec(&probe_count);
	wake_up(&probe_waitqueue);
	return ret;
}

在该函数内部将usb通用驱动程序函数generic_probe,关于该函数的注册详见:点击打开链接,这里直接进入该函数内部分析。

6. generic_probe()

static int generic_probe(struct usb_device *udev)
{
	int err, c;

	/* Choose and set the configuration.  This registers the interfaces
	 * with the driver core and lets interface drivers bind to them.
	 */
	if (udev->authorized == 0)
		dev_err(&udev->dev, "Device is not authorized for usage\n");
	else {
		c = usb_choose_configuration(udev); //选择配置
		if (c >= 0) {
			err = usb_set_configuration(udev, c); //设置配置
			if (err && err != -ENODEV) {
				dev_err(&udev->dev, "can't set config #%d, error %d\n",
					c, err);
				/* This need not be fatal.  The user can try to
				 * set other configurations. */
			}
		}
	}
	/* USB device state == configured ... usable */
	usb_notify_add_device(udev);

	return 0;
}

6.1 usb_choose_configuration()

int usb_choose_configuration(struct usb_device *udev)
{
	int i;
	int num_configs;
	int insufficient_power = 0;
	struct usb_host_config *c, *best;

	if (usb_device_is_owned(udev))
		return 0;

	best = NULL;
	c = udev->config; //获取配置的指针
	num_configs = udev->descriptor.bNumConfigurations; //通过打印的报文,确定配置个数为1个
	for (i = 0; i < num_configs; (i++, c++)) {
		struct usb_interface_descriptor	*desc = NULL;

		/* It's possible that a config has no interfaces! */
		if (c->desc.bNumInterfaces > 0) //获取配置的接口数
			desc = &c->intf_cache[0]->altsetting->desc;

		/*
		 * HP's USB bus-powered keyboard has only one configuration
		 * and it claims to be self-powered; other devices may have
		 * similar errors in their descriptors.  If the next test
		 * were allowed to execute, such configurations would always
		 * be rejected and the devices would not work as expected.
		 * In the meantime, we run the risk of selecting a config
		 * that requires external power at a time when that power
		 * isn't available.  It seems to be the lesser of two evils.
		 *
		 * Bugzilla #6448 reports a device that appears to crash
		 * when it receives a GET_DEVICE_STATUS request!  We don't
		 * have any other way to tell whether a device is self-powered,
		 * but since we don't use that information anywhere but here,
		 * the call has been removed.
		 *
		 * Maybe the GET_DEVICE_STATUS call and the test below can
		 * be reinstated when device firmwares become more reliable.
		 * Don't hold your breath.
		 */
#if 0
		/* Rule out self-powered configs for a bus-powered device */
		if (bus_powered && (c->desc.bmAttributes &
					USB_CONFIG_ATT_SELFPOWER))
			continue;
#endif

		/*
		 * The next test may not be as effective as it should be.
		 * Some hubs have errors in their descriptor, claiming
		 * to be self-powered when they are really bus-powered.
		 * We will overestimate the amount of current such hubs
		 * make available for each port.
		 *
		 * This is a fairly benign sort of failure.  It won't
		 * cause us to reject configurations that we should have
		 * accepted.
		 */

		/* Rule out configs that draw too much bus current */
		if (usb_get_max_power(udev, c) > udev->bus_mA) {
			insufficient_power++;
			continue;
		}

		/* When the first config's first interface is one of Microsoft's
		 * pet nonstandard Ethernet-over-USB protocols, ignore it unless
		 * this kernel has enabled the necessary host side driver.
		 * But: Don't ignore it if it's the only config.
		 */
		if (i == 0 && num_configs > 1 && desc &&
				(is_rndis(desc) || is_activesync(desc))) {
#if !defined(CONFIG_USB_NET_RNDIS_HOST) && !defined(CONFIG_USB_NET_RNDIS_HOST_MODULE)
			continue;
#else
			best = c;
#endif
		}

		/* From the remaining configs, choose the first one whose
		 * first interface is for a non-vendor-specific class.
		 * Reason: Linux is more likely to have a class driver
		 * than a vendor-specific driver. */
		else if (udev->descriptor.bDeviceClass != //USB分配的设备类代码,0x01~0xfe为标准设备类,0xff为厂商自定义类型  
						USB_CLASS_VENDOR_SPEC &&
				(desc && desc->bInterfaceClass !=
						USB_CLASS_VENDOR_SPEC)) {
			best = c;
			break;
		}

		/* If all the remaining configs are vendor-specific,
		 * choose the first one. */
		else if (!best)
			best = c;
	}

	if (insufficient_power > 0)
		dev_info(&udev->dev, "rejected %d configuration%s "
			"due to insufficient available bus power\n",
			insufficient_power, plural(insufficient_power));

	if (best) {
		i = best->desc.bConfigurationValue;
		dev_dbg(&udev->dev,
			"configuration #%d chosen from %d choice%s\n",
			i, num_configs, plural(num_configs));
	} else {
		i = -1;
		dev_warn(&udev->dev,
			"no configuration chosen from %d choice%s\n",
			num_configs, plural(num_configs));
	}
	return i;
}
该函数的功能是从usb的设备中获取一个有效的配置,如果成功将返回配置序号,i = best->desc.bConfigurationValue。

6.2 usb_set_configuration()

int usb_set_configuration(struct usb_device *dev, int configuration)
{
	int i, ret;
	struct usb_host_config *cp = NULL;
	struct usb_interface **new_interfaces = NULL;
	struct usb_hcd *hcd = bus_to_hcd(dev->bus);
	int n, nintf;

	if (dev->authorized == 0 || configuration == -1)
		configuration = 0;
	else {
		for (i = 0; i < dev->descriptor.bNumConfigurations; i++) {
			if (dev->config[i].desc.bConfigurationValue ==
					configuration) { //在usb_choose_configuration()函数中返回了配置序号configuration,这里是通过配置序号找到对应的配置
				cp = &dev->config[i];
				break;
			}
		}
	}
	if ((!cp && configuration != 0))
		return -EINVAL;

	/* The USB spec says configuration 0 means unconfigured.
	 * But if a device includes a configuration numbered 0,
	 * we will accept it as a correctly configured state.
	 * Use -1 if you really want to unconfigure the device.
	 */
	if (cp && configuration == 0)
		dev_warn(&dev->dev, "config 0 descriptor??\n");

	/* Allocate memory for new interfaces before doing anything else,
	 * so that if we run out then nothing will have changed. */
	n = nintf = 0;
	if (cp) {
		nintf = cp->desc.bNumInterfaces; //获取配置里的接口个数
		new_interfaces = kmalloc(nintf * sizeof(*new_interfaces),  //分配nintf个接口指针
				GFP_NOIO);
		if (!new_interfaces) {
			dev_err(&dev->dev, "Out of memory\n");
			return -ENOMEM;
		}

		//给每个接口分配内存空间
		for (; n < nintf; ++n) { //遍历接口个数
			new_interfaces[n] = kzalloc( //给每个接口分配空间
					sizeof(struct usb_interface),
					GFP_NOIO);
			if (!new_interfaces[n]) {
				dev_err(&dev->dev, "Out of memory\n");
				ret = -ENOMEM;
free_interfaces:
				while (--n >= 0)
					kfree(new_interfaces[n]);
				kfree(new_interfaces);
				return ret;
			}
		}

		i = dev->bus_mA - usb_get_max_power(dev, cp); //i = 枚举时获取到的电流-最大的标准电流
		if (i < 0)
			dev_warn(&dev->dev, "new config #%d exceeds power "
					"limit by %dmA\n",
					configuration, -i);
	}

	/* Wake up the device so we can send it the Set-Config request */
	ret = usb_autoresume_device(dev);
	if (ret)
		goto free_interfaces;

	/* if it's already configured, clear out old state first.
	 * getting rid of old interfaces means unbinding their drivers.
	 */
	if (dev->state != USB_STATE_ADDRESS)
		usb_disable_device(dev, 1);	/* Skip ep0 */

	/* Get rid of pending async Set-Config requests for this device */
	cancel_async_set_config(dev);

	/* Make sure we have bandwidth (and available HCD resources) for this
	 * configuration.  Remove endpoints from the schedule if we're dropping
	 * this configuration to set configuration 0.  After this point, the
	 * host controller will not allow submissions to dropped endpoints.  If
	 * this call fails, the device state is unchanged.
	 */
	mutex_lock(hcd->bandwidth_mutex);
	/* Disable LPM, and re-enable it once the new configuration is
	 * installed, so that the xHCI driver can recalculate the U1/U2
	 * timeouts.
	 */
	if (dev->actconfig && usb_disable_lpm(dev)) {
		dev_err(&dev->dev, "%s Failed to disable LPM\n.", __func__);
		mutex_unlock(hcd->bandwidth_mutex);
		ret = -ENOMEM;
		goto free_interfaces;
	}
	ret = usb_hcd_alloc_bandwidth(dev, cp, NULL, NULL);
	if (ret < 0) {
		if (dev->actconfig)
			usb_enable_lpm(dev);
		mutex_unlock(hcd->bandwidth_mutex);
		usb_autosuspend_device(dev);
		goto free_interfaces;
	}

	/*
	 * Initialize the new interface structures and the
	 * hc/hcd/usbcore interface/endpoint state.
	 */
	//遍历接口,为初始化接口设备,绑定设备类型为接口!!!
	for (i = 0; i < nintf; ++i) { 
		struct usb_interface_cache *intfc;
		struct usb_interface *intf;
		struct usb_host_interface *alt;

		cp->interface[i] = intf = new_interfaces[i];
		intfc = cp->intf_cache[i];
		intf->altsetting = intfc->altsetting;
		intf->num_altsetting = intfc->num_altsetting;
		kref_get(&intfc->ref);

		alt = usb_altnum_to_altsetting(intf, 0);

		/* No altsetting 0?  We'll assume the first altsetting.
		 * We could use a GetInterface call, but if a device is
		 * so non-compliant that it doesn't have altsetting 0
		 * then I wouldn't trust its reply anyway.
		 */
		if (!alt)
			alt = &intf->altsetting[0];

		intf->intf_assoc =
			find_iad(dev, cp, alt->desc.bInterfaceNumber);
		intf->cur_altsetting = alt;
		usb_enable_interface(dev, intf, true);
		intf->dev.parent = &dev->dev;
		intf->dev.driver = NULL;
		intf->dev.bus = &usb_bus_type; //将当前设备绑定总线为USB
		intf->dev.type = &usb_if_device_type; //设备类型为接口
		intf->dev.groups = usb_interface_groups; //usb接口类型为组
		intf->dev.dma_mask = dev->dev.dma_mask;
		INIT_WORK(&intf->reset_ws, __usb_queue_reset_device);
		intf->minor = -1;
		device_initialize(&intf->dev); //设备模型初始化
		pm_runtime_no_callbacks(&intf->dev);
		dev_set_name(&intf->dev, "%d-%s:%d.%d",
			dev->bus->busnum, dev->devpath,
			configuration, alt->desc.bInterfaceNumber);
	}
	kfree(new_interfaces);

	//设置主机控制器上的配置索引
	ret = usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
			      USB_REQ_SET_CONFIGURATION, 0, configuration, 0,
			      NULL, 0, USB_CTRL_SET_TIMEOUT);
	if (ret < 0 && cp) {
		/*
		 * All the old state is gone, so what else can we do?
		 * The device is probably useless now anyway.
		 */
		usb_hcd_alloc_bandwidth(dev, NULL, NULL, NULL);
		for (i = 0; i < nintf; ++i) {
			usb_disable_interface(dev, cp->interface[i], true);
			put_device(&cp->interface[i]->dev);
			cp->interface[i] = NULL;
		}
		cp = NULL;
	}

	dev->actconfig = cp; //绑定实际的配置
	mutex_unlock(hcd->bandwidth_mutex);

	if (!cp) {
		usb_set_device_state(dev, USB_STATE_ADDRESS);

		/* Leave LPM disabled while the device is unconfigured. */
		usb_autosuspend_device(dev);
		return ret;
	}
	usb_set_device_state(dev, USB_STATE_CONFIGURED);

	if (cp->string == NULL &&
			!(dev->quirks & USB_QUIRK_CONFIG_INTF_STRINGS))
		cp->string = usb_cache_string(dev, cp->desc.iConfiguration);

	/* Now that the interfaces are installed, re-enable LPM. */
	usb_unlocked_enable_lpm(dev);
	/* Enable LTM if it was turned off by usb_disable_device. */
	usb_enable_ltm(dev);

	/* Now that all the interfaces are set up, register them
	 * to trigger binding of drivers to interfaces.  probe()
	 * routines may install different altsettings and may
	 * claim() any interfaces not yet bound.  Many class drivers
	 * need that: CDC, audio, video, etc.
	 */

	//遍历接口,注册接口到usb总线上,同时匹配对应的驱动
	for (i = 0; i < nintf; ++i) {
		struct usb_interface *intf = cp->interface[i];

		dev_dbg(&dev->dev,
			"adding %s (config #%d, interface %d)\n",
			dev_name(&intf->dev), configuration,
			intf->cur_altsetting->desc.bInterfaceNumber);
		device_enable_async_suspend(&intf->dev);
		ret = device_add(&intf->dev); //又是熟悉的接口函数
		if (ret != 0) {
			dev_err(&dev->dev, "device_add(%s) --> %d\n",
				dev_name(&intf->dev), ret);
			continue;
		}
		create_intf_ep_devs(intf);
	}

	usb_autosuspend_device(dev);
	return 0;
}
该函数的主要功能时为配置下的每个接口分配内存空间,然后遍历每一个接口,为每一个接口初始化设备模型,包括usb总线的绑定,设备类型绑定为接口,最后为每个接口进行usb总线上的注册
intf->dev.bus = &usb_bus_type; //将当前设备绑定总线为USB
intf->dev.type = &usb_if_device_type; //设备类型为接口
intf->dev.groups = usb_interface_groups; //usb接口类型为组
......
ret = device_add(&intf->dev);
这里我们又见到了非常熟悉的device_add函数,关于该函数我们在上面的“5.4.1小节”有详细的分析,这里最终在match函数内部将调用的是接口,再次贴出源码方便分析!
static int usb_device_match(struct device *dev, struct device_driver *drv)  
{  
    /* devices and interfaces are handled separately */  
    if (is_usb_device(dev)) { //是否是usb设备  
  
        /* interface drivers never match devices */  
        if (!is_usb_device_driver(drv))  
            return 0;  
  
        /* TODO: Add real matching code */  
        return 1;  
  
    } else if (is_usb_interface(dev)) { //是否是usb接口  
        struct usb_interface *intf;  
        struct usb_driver *usb_drv;  
        const struct usb_device_id *id;  
  
        /* device drivers never match interfaces */  
        if (is_usb_device_driver(drv))   //条件过滤
            return 0;  
  
        intf = to_usb_interface(dev);  
        usb_drv = to_usb_driver(drv);  
  
        id = usb_match_id(intf, usb_drv->id_table);  //将当前接口与对应的驱动id_table表进行匹配
        if (id)  
            return 1;  
  
        id = usb_match_dynamic_id(intf, usb_drv);  
        if (id)  
            return 1;  
    }  
  
    return 0;  
}  
该函数内部我们最关心的函数是
id = usb_match_id(intf, usb_drv->id_table);  //将当前接口与对应的驱动id_table表进行匹配
该函数两个参数,一个为当前的接口设备,另外一个为usb的驱动id_table表,当接口设备和id_table表中的id匹配后将调用usb_drv的probe探测函数,我们这里以usb转串口驱动分析,详见usb转串口驱动分析路径: 点击打开链接

7. usb_match_id()接口匹配

const struct usb_device_id *usb_match_id(struct usb_interface *interface,
					 const struct usb_device_id *id)
{
	/* proc_connectinfo in devio.c may call us with id == NULL. */
	if (id == NULL)
		return NULL;

	/* It is important to check that id->driver_info is nonzero,
	   since an entry that is all zeroes except for a nonzero
	   id->driver_info is the way to create an entry that
	   indicates that the driver want to examine every
	   device and interface. */
	for (; id->idVendor || id->idProduct || id->bDeviceClass ||
	       id->bInterfaceClass || id->driver_info; id++) {
		if (usb_match_one_id(interface, id)) //见下分析
			return id;
	}

	return NULL;
}
EXPORT_SYMBOL_GPL(usb_match_id);
int usb_match_device(struct usb_device *dev, const struct usb_device_id *id)
{
	if ((id->match_flags & USB_DEVICE_ID_MATCH_VENDOR) &&
	    id->idVendor != le16_to_cpu(dev->descriptor.idVendor))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_PRODUCT) &&
	    id->idProduct != le16_to_cpu(dev->descriptor.idProduct))
		return 0;

	/* No need to test id->bcdDevice_lo != 0, since 0 is never
	   greater than any unsigned number. */
	if ((id->match_flags & USB_DEVICE_ID_MATCH_DEV_LO) &&
	    (id->bcdDevice_lo > le16_to_cpu(dev->descriptor.bcdDevice)))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_DEV_HI) &&
	    (id->bcdDevice_hi < le16_to_cpu(dev->descriptor.bcdDevice)))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_DEV_CLASS) &&
	    (id->bDeviceClass != dev->descriptor.bDeviceClass))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_DEV_SUBCLASS) &&
	    (id->bDeviceSubClass != dev->descriptor.bDeviceSubClass))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_DEV_PROTOCOL) &&
	    (id->bDeviceProtocol != dev->descriptor.bDeviceProtocol))
		return 0;

	return 1;
}
该函数主要时完成id字段匹配,寻找对应的驱动,如果这里匹配成功,将调用usb_if_device_type类型。

8. usb_probe_interface()接口探测函数

static int usb_probe_interface(struct device *dev)
{
	struct usb_driver *driver = to_usb_driver(dev->driver);
	struct usb_interface *intf = to_usb_interface(dev);
	struct usb_device *udev = interface_to_usbdev(intf);
	const struct usb_device_id *id;
	int error = -ENODEV;
	int lpm_disable_error;

	dev_dbg(dev, "%s\n", __func__);

	intf->needs_binding = 0;

	if (usb_device_is_owned(udev))
		return error;

	if (udev->authorized == 0) {
		dev_err(&intf->dev, "Device is not authorized for usage\n");
		return error;
	}

	id = usb_match_id(intf, driver->id_table); //driver->id_table是哪里赋值的???
	if (!id)
		id = usb_match_dynamic_id(intf, driver);
	if (!id)
		return error;

	dev_dbg(dev, "%s - got id\n", __func__);

	error = usb_autoresume_device(udev);
	if (error)
		return error;

	intf->condition = USB_INTERFACE_BINDING;

	/* Probed interfaces are initially active.  They are
	 * runtime-PM-enabled only if the driver has autosuspend support.
	 * They are sensitive to their children's power states.
	 */
	pm_runtime_set_active(dev);
	pm_suspend_ignore_children(dev, false);
	if (driver->supports_autosuspend)
		pm_runtime_enable(dev);

	/* If the new driver doesn't allow hub-initiated LPM, and we can't
	 * disable hub-initiated LPM, then fail the probe.
	 *
	 * Otherwise, leaving LPM enabled should be harmless, because the
	 * endpoint intervals should remain the same, and the U1/U2 timeouts
	 * should remain the same.
	 *
	 * If we need to install alt setting 0 before probe, or another alt
	 * setting during probe, that should also be fine.  usb_set_interface()
	 * will attempt to disable LPM, and fail if it can't disable it.
	 */
	lpm_disable_error = usb_unlocked_disable_lpm(udev);
	if (lpm_disable_error && driver->disable_hub_initiated_lpm) {
		dev_err(&intf->dev, "%s Failed to disable LPM for driver %s\n.",
				__func__, driver->name);
		error = lpm_disable_error;
		goto err;
	}

	/* Carry out a deferred switch to altsetting 0 */
	if (intf->needs_altsetting0) {
		error = usb_set_interface(udev, intf->altsetting[0].
				desc.bInterfaceNumber, 0);
		if (error < 0)
			goto err;
		intf->needs_altsetting0 = 0;
	}

	error = driver->probe(intf, id); //这里将调用usb_serial_probe()
	if (error)
		goto err;

	intf->condition = USB_INTERFACE_BOUND;

	/* If the LPM disable succeeded, balance the ref counts. */
	if (!lpm_disable_error)
		usb_unlocked_enable_lpm(udev);

	usb_autosuspend_device(udev);
	return error;

 err:
	usb_set_intfdata(intf, NULL);
	intf->needs_remote_wakeup = 0;
	intf->condition = USB_INTERFACE_UNBOUND;
	usb_cancel_queued_reset(intf);

	/* If the LPM disable succeeded, balance the ref counts. */
	if (!lpm_disable_error)
		usb_unlocked_enable_lpm(udev);

	/* Unbound interfaces are always runtime-PM-disabled and -suspended */
	if (driver->supports_autosuspend)
		pm_runtime_disable(dev);
	pm_runtime_set_suspended(dev);

	usb_autosuspend_device(udev);
	return error;
}

该接口探测函数的主要功能是通过usb_match_id(intf, driver->id_table),从id_table表中匹配与接口对应的id,如果成功将调用如下探测函数指针:

error = driver->probe(intf, id); //这里将调用usb_serial_probe()
为什么这里会调用usb_serial_probe函数,需要分析options.c文件是如何注册到usb总线上的???我猜想,应该时usb_serial_probe对应的结构体注册到了usb总线上,而usb_serial_probe自身又在“usb-serial”总线上,所以在匹配时是先匹配对应的usb总线上的驱动,然后才匹配对应的usb-serial总线上的驱动

9. usb_serial_probe() usb串口探测函数

static int usb_serial_probe(struct usb_interface *interface,
			       const struct usb_device_id *id)
{
	struct device *ddev = &interface->dev;
	struct usb_device *dev = interface_to_usbdev(interface);
	struct usb_serial *serial = NULL;
	struct usb_serial_port *port;
	struct usb_host_interface *iface_desc;
	struct usb_endpoint_descriptor *endpoint;
	struct usb_endpoint_descriptor *interrupt_in_endpoint[MAX_NUM_PORTS];
	struct usb_endpoint_descriptor *interrupt_out_endpoint[MAX_NUM_PORTS];
	struct usb_endpoint_descriptor *bulk_in_endpoint[MAX_NUM_PORTS];
	struct usb_endpoint_descriptor *bulk_out_endpoint[MAX_NUM_PORTS];
	struct usb_serial_driver *type = NULL;
	int retval;
	unsigned int minor;
	int buffer_size;
	int i;
	int j;
	int num_interrupt_in = 0;
	int num_interrupt_out = 0;
	int num_bulk_in = 0;
	int num_bulk_out = 0;
	int num_ports = 0;
	int max_endpoints;

	mutex_lock(&table_lock);
	type = search_serial_device(interface); //根据接口,从usb_serial_driver_list链表中搜索匹配的id对应的驱动
	if (!type) {
		mutex_unlock(&table_lock);
		dev_dbg(ddev, "none matched\n");
		return -ENODEV;
	}

	if (!try_module_get(type->driver.owner)) {
		mutex_unlock(&table_lock);
		dev_err(ddev, "module get failed, exiting\n");
		return -EIO;
	}
	mutex_unlock(&table_lock);

	serial = create_serial(dev, interface, type);
	if (!serial) {
		module_put(type->driver.owner);
		return -ENOMEM;
	}

	/* if this device type has a probe function, call it */
	if (type->probe) {
		const struct usb_device_id *id;

		id = get_iface_id(type, interface);
		retval = type->probe(serial, id); //调用上面匹配到的驱动探测函数

		if (retval) {
			dev_dbg(ddev, "sub driver rejected device\n");
			usb_serial_put(serial);
			module_put(type->driver.owner);
			return retval;
		}
	}

	/* descriptor matches, let's find the endpoints needed */
	/* check out the endpoints */
	iface_desc = interface->cur_altsetting;
	for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
		endpoint = &iface_desc->endpoint[i].desc;

		if (usb_endpoint_is_bulk_in(endpoint)) {
			/* we found a bulk in endpoint */
			dev_dbg(ddev, "found bulk in on endpoint %d\n", i);
			bulk_in_endpoint[num_bulk_in] = endpoint;
			++num_bulk_in;
		}

		if (usb_endpoint_is_bulk_out(endpoint)) {
			/* we found a bulk out endpoint */
			dev_dbg(ddev, "found bulk out on endpoint %d\n", i);
			bulk_out_endpoint[num_bulk_out] = endpoint;
			++num_bulk_out;
		}

		if (usb_endpoint_is_int_in(endpoint)) {
			/* we found a interrupt in endpoint */
			dev_dbg(ddev, "found interrupt in on endpoint %d\n", i);
			interrupt_in_endpoint[num_interrupt_in] = endpoint;
			++num_interrupt_in;
		}

		if (usb_endpoint_is_int_out(endpoint)) {
			/* we found an interrupt out endpoint */
			dev_dbg(ddev, "found interrupt out on endpoint %d\n", i);
			interrupt_out_endpoint[num_interrupt_out] = endpoint;
			++num_interrupt_out;
		}
	}

#if defined(CONFIG_USB_SERIAL_PL2303) || defined(CONFIG_USB_SERIAL_PL2303_MODULE)
	/* BEGIN HORRIBLE HACK FOR PL2303 */
	/* this is needed due to the looney way its endpoints are set up */
	if (((le16_to_cpu(dev->descriptor.idVendor) == PL2303_VENDOR_ID) &&
	     (le16_to_cpu(dev->descriptor.idProduct) == PL2303_PRODUCT_ID)) ||
	    ((le16_to_cpu(dev->descriptor.idVendor) == ATEN_VENDOR_ID) &&
	     (le16_to_cpu(dev->descriptor.idProduct) == ATEN_PRODUCT_ID)) ||
	    ((le16_to_cpu(dev->descriptor.idVendor) == ALCOR_VENDOR_ID) &&
	     (le16_to_cpu(dev->descriptor.idProduct) == ALCOR_PRODUCT_ID)) ||
	    ((le16_to_cpu(dev->descriptor.idVendor) == SIEMENS_VENDOR_ID) &&
	     (le16_to_cpu(dev->descriptor.idProduct) == SIEMENS_PRODUCT_ID_EF81))) {
		if (interface != dev->actconfig->interface[0]) {
			/* check out the endpoints of the other interface*/
			iface_desc = dev->actconfig->interface[0]->cur_altsetting;
			for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
				endpoint = &iface_desc->endpoint[i].desc;
				if (usb_endpoint_is_int_in(endpoint)) {
					/* we found a interrupt in endpoint */
					dev_dbg(ddev, "found interrupt in for Prolific device on separate interface\n");
					interrupt_in_endpoint[num_interrupt_in] = endpoint;
					++num_interrupt_in;
				}
			}
		}

		/* Now make sure the PL-2303 is configured correctly.
		 * If not, give up now and hope this hack will work
		 * properly during a later invocation of usb_serial_probe
		 */
		if (num_bulk_in == 0 || num_bulk_out == 0) {
			dev_info(ddev, "PL-2303 hack: descriptors matched but endpoints did not\n");
			usb_serial_put(serial);
			module_put(type->driver.owner);
			return -ENODEV;
		}
	}
	/* END HORRIBLE HACK FOR PL2303 */
#endif

#ifdef CONFIG_USB_SERIAL_GENERIC
	if (type == &usb_serial_generic_device) {
		num_ports = num_bulk_out;
		if (num_ports == 0) {
			dev_err(ddev, "Generic device with no bulk out, not allowed.\n");
			usb_serial_put(serial);
			module_put(type->driver.owner);
			return -EIO;
		}
		dev_info(ddev, "The \"generic\" usb-serial driver is only for testing and one-off prototypes.\n");
		dev_info(ddev, "Tell [email protected] to add your device to a proper driver.\n");
	}
#endif
	if (!num_ports) {
		/* if this device type has a calc_num_ports function, call it */
		if (type->calc_num_ports)
			num_ports = type->calc_num_ports(serial);
		if (!num_ports)
			num_ports = type->num_ports;
	}

	serial->num_ports = num_ports;
	serial->num_bulk_in = num_bulk_in;
	serial->num_bulk_out = num_bulk_out;
	serial->num_interrupt_in = num_interrupt_in;
	serial->num_interrupt_out = num_interrupt_out;

	/* found all that we need */
	dev_info(ddev, "%s converter detected\n", type->description);

	/* create our ports, we need as many as the max endpoints */
	/* we don't use num_ports here because some devices have more
	   endpoint pairs than ports */
	max_endpoints = max(num_bulk_in, num_bulk_out);
	max_endpoints = max(max_endpoints, num_interrupt_in);
	max_endpoints = max(max_endpoints, num_interrupt_out);
	max_endpoints = max(max_endpoints, (int)serial->num_ports);
	serial->num_port_pointers = max_endpoints;

	dev_dbg(ddev, "setting up %d port structures for this device", max_endpoints);
	for (i = 0; i < max_endpoints; ++i) {
		port = kzalloc(sizeof(struct usb_serial_port), GFP_KERNEL);
		if (!port)
			goto probe_error;
		tty_port_init(&port->port);
		port->port.ops = &serial_port_ops;
		port->serial = serial;
		spin_lock_init(&port->lock);
		/* Keep this for private driver use for the moment but
		   should probably go away */
		INIT_WORK(&port->work, usb_serial_port_work);
		serial->port[i] = port;
		port->dev.parent = &interface->dev;
		port->dev.driver = NULL;
		port->dev.bus = &usb_serial_bus_type;
		port->dev.release = &usb_serial_port_release;
		device_initialize(&port->dev);
	}

	/* set up the endpoint information */
	for (i = 0; i < num_bulk_in; ++i) {
		endpoint = bulk_in_endpoint[i];
		port = serial->port[i];
		buffer_size = max_t(int, serial->type->bulk_in_size,
				usb_endpoint_maxp(endpoint));
		port->bulk_in_size = buffer_size;
		port->bulk_in_endpointAddress = endpoint->bEndpointAddress;

		for (j = 0; j < ARRAY_SIZE(port->read_urbs); ++j) {
			set_bit(j, &port->read_urbs_free);
			port->read_urbs[j] = usb_alloc_urb(0, GFP_KERNEL);
			if (!port->read_urbs[j])
				goto probe_error;
			port->bulk_in_buffers[j] = kmalloc(buffer_size,
								GFP_KERNEL);
			if (!port->bulk_in_buffers[j])
				goto probe_error;
			usb_fill_bulk_urb(port->read_urbs[j], dev,
					usb_rcvbulkpipe(dev,
						endpoint->bEndpointAddress),
					port->bulk_in_buffers[j], buffer_size,
					serial->type->read_bulk_callback,
					port);
		}

		port->read_urb = port->read_urbs[0];
		port->bulk_in_buffer = port->bulk_in_buffers[0];
	}

	for (i = 0; i < num_bulk_out; ++i) {
		endpoint = bulk_out_endpoint[i];
		port = serial->port[i];
		if (kfifo_alloc(&port->write_fifo, PAGE_SIZE, GFP_KERNEL))
			goto probe_error;
		buffer_size = serial->type->bulk_out_size;
		if (!buffer_size)
			buffer_size = usb_endpoint_maxp(endpoint);
		port->bulk_out_size = buffer_size;
		port->bulk_out_endpointAddress = endpoint->bEndpointAddress;

		for (j = 0; j < ARRAY_SIZE(port->write_urbs); ++j) {
			set_bit(j, &port->write_urbs_free);
			port->write_urbs[j] = usb_alloc_urb(0, GFP_KERNEL);
			if (!port->write_urbs[j])
				goto probe_error;
			port->bulk_out_buffers[j] = kmalloc(buffer_size,
								GFP_KERNEL);
			if (!port->bulk_out_buffers[j])
				goto probe_error;
			usb_fill_bulk_urb(port->write_urbs[j], dev,
					usb_sndbulkpipe(dev,
						endpoint->bEndpointAddress),
					port->bulk_out_buffers[j], buffer_size,
					serial->type->write_bulk_callback,
					port);
		}

		port->write_urb = port->write_urbs[0];
		port->bulk_out_buffer = port->bulk_out_buffers[0];
	}

	if (serial->type->read_int_callback) {
		for (i = 0; i < num_interrupt_in; ++i) {
			endpoint = interrupt_in_endpoint[i];
			port = serial->port[i];
			port->interrupt_in_urb = usb_alloc_urb(0, GFP_KERNEL);
			if (!port->interrupt_in_urb)
				goto probe_error;
			buffer_size = usb_endpoint_maxp(endpoint);
			port->interrupt_in_endpointAddress =
						endpoint->bEndpointAddress;
			port->interrupt_in_buffer = kmalloc(buffer_size,
								GFP_KERNEL);
			if (!port->interrupt_in_buffer)
				goto probe_error;
			usb_fill_int_urb(port->interrupt_in_urb, dev,
				usb_rcvintpipe(dev,
						endpoint->bEndpointAddress),
				port->interrupt_in_buffer, buffer_size,
				serial->type->read_int_callback, port,
				endpoint->bInterval);
		}
	} else if (num_interrupt_in) {
		dev_dbg(ddev, "The device claims to support interrupt in transfers, but read_int_callback is not defined\n");
	}

	if (serial->type->write_int_callback) {
		for (i = 0; i < num_interrupt_out; ++i) {
			endpoint = interrupt_out_endpoint[i];
			port = serial->port[i];
			port->interrupt_out_urb = usb_alloc_urb(0, GFP_KERNEL);
			if (!port->interrupt_out_urb)
				goto probe_error;
			buffer_size = usb_endpoint_maxp(endpoint);
			port->interrupt_out_size = buffer_size;
			port->interrupt_out_endpointAddress =
						endpoint->bEndpointAddress;
			port->interrupt_out_buffer = kmalloc(buffer_size,
								GFP_KERNEL);
			if (!port->interrupt_out_buffer)
				goto probe_error;
			usb_fill_int_urb(port->interrupt_out_urb, dev,
				usb_sndintpipe(dev,
						  endpoint->bEndpointAddress),
				port->interrupt_out_buffer, buffer_size,
				serial->type->write_int_callback, port,
				endpoint->bInterval);
		}
	} else if (num_interrupt_out) {
		dev_dbg(ddev, "The device claims to support interrupt out transfers, but write_int_callback is not defined\n");
	}

	usb_set_intfdata(interface, serial);

	/* if this device type has an attach function, call it */
	if (type->attach) {
		retval = type->attach(serial);
		if (retval < 0)
			goto probe_error;
		serial->attached = 1;
		if (retval > 0) {
			/* quietly accept this device, but don't bind to a
			   serial port as it's about to disappear */
			serial->num_ports = 0;
			goto exit;
		}
	} else {
		serial->attached = 1;
	}

	/* Avoid race with tty_open and serial_install by setting the
	 * disconnected flag and not clearing it until all ports have been
	 * registered.
	 */
	serial->disconnected = 1;

	if (get_free_serial(serial, num_ports, &minor) == NULL) {
		dev_err(ddev, "No more free serial devices\n");
		goto probe_error;
	}
	serial->minor = minor;

	/* register all of the individual ports with the driver core */
	for (i = 0; i < num_ports; ++i) {
		port = serial->port[i];
		dev_set_name(&port->dev, "ttyUSB%d", port->number);
		dev_dbg(ddev, "registering %s", dev_name(&port->dev));
		device_enable_async_suspend(&port->dev);

		retval = device_add(&port->dev);
		if (retval)
			dev_err(ddev, "Error registering port device, continuing\n");
	}

	serial->disconnected = 0;

	usb_serial_console_init(minor);
exit:
	module_put(type->driver.owner);
	return 0;

probe_error:
	usb_serial_put(serial);
	module_put(type->driver.owner);
	return -EIO;
}
该函数usb_serial_probe()主要通过search_serial_device()函数遍历链表usb_serial_driver_list链表,根据ID寻找匹配的驱动,如下源码:
static struct usb_serial_driver *search_serial_device(
					struct usb_interface *iface)
{
	const struct usb_device_id *id = NULL;
	struct usb_serial_driver *drv;
	struct usb_driver *driver = to_usb_driver(iface->dev.driver);

	/* Check if the usb id matches a known device */
	list_for_each_entry(drv, &usb_serial_driver_list, driver_list) {
		if (drv->usb_driver == driver)
			id = get_iface_id(drv, iface); //见下
		if (id)
			return drv;
	}

	return NULL;
}
static const struct usb_device_id *get_iface_id(struct usb_serial_driver *drv,
						struct usb_interface *intf)
{
	const struct usb_device_id *id;

	id = usb_match_id(intf, drv->id_table);
	if (id) {
		dev_dbg(&intf->dev, "static descriptor matches\n");
		goto exit;
	}
	id = match_dynamic_id(intf, drv);
	if (id)
		dev_dbg(&intf->dev, "dynamic descriptor matches\n");
exit:
	return id;
}
如果接口和驱动匹配成功,将调用驱动的探测函数,如下源码:
	if (type->probe) {
		const struct usb_device_id *id;

		id = get_iface_id(type, interface);
		retval = type->probe(serial, id); //调用上面匹配到的驱动探测函数

		if (retval) {
			dev_dbg(ddev, "sub driver rejected device\n");
			usb_serial_put(serial);
			module_put(type->driver.owner);
			return retval;
		}
	}
最后是统计端点是否为批量或中断端点的个数,最后通过该端点创建相应的信息......
我们再回到上面的函数:
retval = type->probe(serial, id); //调用上面匹配到的驱动探测函数

这里将调用options.c的探测函数,这个函数也是我们最终的根源,不容易!!!

10. option_probe()

static int option_probe(struct usb_serial *serial,
			const struct usb_device_id *id)
{
	struct usb_interface_descriptor *iface_desc =
				&serial->interface->cur_altsetting->desc;
	struct usb_device_descriptor *dev_desc = &serial->dev->descriptor;

	/* Never bind to the CD-Rom emulation interface	*/
	if (iface_desc->bInterfaceClass == 0x08)
		return -ENODEV;

	/*
	 * Don't bind reserved interfaces (like network ones) which often have
	 * the same class/subclass/protocol as the serial interfaces.  Look at
	 * the Windows driver .INF files for reserved interface numbers.
	 */
	if (is_blacklisted(
		iface_desc->bInterfaceNumber,
		OPTION_BLACKLIST_RESERVED_IF,
		(const struct option_blacklist_info *) id->driver_info))
		return -ENODEV;
	/*
	 * Don't bind network interface on Samsung GT-B3730, it is handled by
	 * a separate module.
	 */
	if (dev_desc->idVendor == cpu_to_le16(SAMSUNG_VENDOR_ID) &&
	    dev_desc->idProduct == cpu_to_le16(SAMSUNG_PRODUCT_GT_B3730) &&
	    iface_desc->bInterfaceClass != USB_CLASS_CDC_DATA)
		return -ENODEV;

	/* Store device id so we can use it during attach. */
	usb_set_serial_data(serial, (void *)id);

	return 0;
}
      至此,就完成了usb主机控制器上结束设备时的分析过程,本篇博客涉及的内容较多,但流程比较明确,先是线程检测到链表有变化-->设备枚举-->设备和驱动的匹配-->后面是接口和驱动的匹配-->再后来是调用usb_serial_probe-->再后来是调用option_probe。从上面第9节开始,没有详细的分析源码,只是简单的描述了usb物理口上接入设备的的创建过程,由于usb串口驱动篇幅较多,这里另起一篇博客,详见: 点击打开链接












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