mini2440 usb host device controller驱动分析（四）-----root hub驱动的分析（二）

接下来开始讲设备的枚举过程。

前面分析了root hub感应设备插拔的过程。root hub还有一个功能是对新插入的设备进行枚举。其实root hub完成了枚举的前几个步骤：get descriptor  、 set address 、 get configuration。 枚举的后面几个步骤是由上层的class driver来完成的，这个后面在分析。

在前面的hub_port_connect_change中调用了hub_port_init中，我们可以看到这个枚举的过程。 

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;
	char 			*speed, *type;
	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);
		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].
	 */
	switch (udev->speed) {
	case USB_SPEED_SUPER:
	case USB_SPEED_VARIABLE:	/* 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;
	}
 
	type = "";
	switch (udev->speed) {
	case USB_SPEED_LOW:	speed = "low";	break;
	case USB_SPEED_FULL:	speed = "full";	break;
	case USB_SPEED_HIGH:	speed = "high";	break;
	case USB_SPEED_SUPER:
				speed = "super";
				break;
	case USB_SPEED_VARIABLE:
				speed = "variable";
				type = "Wireless ";
				break;
	default: 		speed = "?";	break;
	}
	if (udev->speed != USB_SPEED_SUPER)
		dev_info(&udev->dev,
				"%s %s speed %sUSB device using %s and address %d\n",
				(udev->config) ? "reset" : "new", speed, type,
				udev->bus->controller->driver->name, devnum);

	/* Set up TT records, if needed  */
	if (hdev->tt) {
		udev->tt = hdev->tt;
		udev->ttport = hdev->ttport;
	} else if (udev->speed != USB_SPEED_HIGH
			&& hdev->speed == USB_SPEED_HIGH) {
		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))) {
		/*
		 * An xHCI controller cannot send any packets to a device until
		 * a set address command successfully completes.
		 */
		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(),
					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;
			kfree(buf);

			retval = hub_port_reset(hub, port1, udev, delay);
			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) {
				dev_err(&udev->dev,
					"device descriptor read/64, error %d\n",
					r);
				retval = -EMSGSIZE;
				continue;
			}
#undef GET_DESCRIPTOR_BUFSIZE
		}

		retval = usb_get_device_descriptor(udev, 8);
	
		break;
		}
	}
	if (retval)
		goto fail;
	if (udev->descriptor.bMaxPacketSize0 == 0xff ||
			udev->speed == USB_SPEED_SUPER)
		i = 512;
	else
		i = udev->descriptor.bMaxPacketSize0;
	if (le16_to_cpu(udev->ep0.desc.wMaxPacketSize) != i) {
		if (udev->speed != USB_SPEED_FULL ||
				!(i == 8 || i == 16 || i == 32 || i == 64)) {
			dev_err(&udev->dev, "ep0 maxpacket = %d\n", i);
			retval = -EMSGSIZE;
			goto fail;
		}
		dev_dbg(&udev->dev, "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);
	if (retval < (signed)sizeof(udev->descriptor)) {
		dev_err(&udev->dev, "device descriptor read/all, error %d\n",
			retval);
		if (retval >= 0)
			retval = -ENOMSG;
		goto fail;
	}

	retval = 0;

fail:
	if (retval) {
		hub_port_disable(hub, port1, 0);
		update_address(udev, devnum);	/* for disconnect processing */
	}
	mutex_unlock(&usb_address0_mutex);
	return retval;
}

上面这个函数中，主要调用了get descriptor 和 set address。并且实现了一个retry的机制，即会多次调用 get descriptor和setaddress，直到成功为止。

这里的set address是给device的udc设置地址，udc专门有一个address寄存器，用于存储它的地址。

此外，每个endpoint也有各自的地址，不知道那个地址是用来做什么的？？

另外，对于新插入的设备，还会调用usb_new_device。在usb_add_device中会调用get configuration。

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

	/* Increment the parent's count of unsuspended children */
	if (udev->parent)
		usb_autoresume_device(udev->parent);

	usb_detect_quirks(udev);		/* Determine quirks */
	err = usb_configure_device(udev);	/* detect & probe dev/intfs */
	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);

	/* 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;
	}

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

fail:
	usb_set_device_state(udev, USB_STATE_NOTATTACHED);
	usb_stop_pm(udev);
	return err;
}

在上面的usb_configure_device中会调用usb_get_configuration. 另外，可以看到usb_create_ep_devs. 也就是说 会给device的ep0也创建一个对应的设备。

到这里，usb root hub 对 设备的枚举过程就结束了。