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<P>#160;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
device_init_wakeup(&amp;udev-&gt;dev, 
0);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
}<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
//如果是从Suspended转到其它状态或者是转到Suspended状态<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
//更新active_duration计数<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if 
(udev-&gt;state == USB_STATE_SUSPENDED 
&amp;&amp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
new_state != 
USB_STATE_SUSPENDED)<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
udev-&gt;active_duration -= 
jiffies;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; else if (new_state 
== USB_STATE_SUSPENDED 
&amp;&amp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
udev-&gt;state != 
USB_STATE_SUSPENDED)<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
udev-&gt;active_duration += 
jiffies;<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
//设置状态<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; udev-&gt;state = 
new_state;<BR>&nbsp;&nbsp;&nbsp;&nbsp; }<BR>&nbsp;&nbsp;&nbsp;&nbsp; 
else<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
//这里是多余的吧?<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
recursively_mark_NOTATTACHED(udev);<BR>&nbsp;&nbsp;&nbsp;&nbsp; 
spin_unlock_irqrestore(&amp;device_state_lock, 
flags);<BR>}<BR>这段代码没有什么好多讲的.就是设置状态而已.对于不是root 
hub的情况,还涉及到了电源管理的情况,在这里不做分析.<BR>&nbsp;<BR>设置完设备状态之后,调用usb_get_device_descriptor()来取得设备描述符.这个函数涉及到数据的传输实现.在接下来的章节中再做详细分析.在这里只需知道,完成之后会将设备描述符存放在usb_dev-&gt;descriptor.<BR>获取到设备描述符之后,就可以获得设备的详细信息了.具体的详细可考阅USB2.0 
spec.在这些信息里会包括设备的配置项数目.因此在接下来的操作中,就会将设备所支持的所有配置取出来.这是在usb_new_device()中完成的.代码如下所示:<BR>int 
usb_new_device(struct usb_device *udev)<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp; int 
err;<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp; 
//一些设备的fixup<BR>&nbsp;&nbsp;&nbsp;&nbsp; 
usb_detect_quirks(udev);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; /* 
Determine quirks */<BR>&nbsp;&nbsp;&nbsp;&nbsp; 
//取得配置描述符<BR>&nbsp;&nbsp;&nbsp;&nbsp; err = 
usb_configure_device(udev);&nbsp;&nbsp;&nbsp; /* detect &amp; probe dev/intfs 
*/<BR>&nbsp;&nbsp;&nbsp;&nbsp; if (err &lt; 
0)<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; goto 
fail;<BR>&nbsp;&nbsp;&nbsp;&nbsp; /* export the usbdev device-node for libusb 
*/<BR>&nbsp;&nbsp;&nbsp;&nbsp; //指定设备的设备号<BR>&nbsp;&nbsp;&nbsp;&nbsp; 
udev-&gt;dev.devt = 
MKDEV(USB_DEVICE_MAJOR,<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
(((udev-&gt;bus-&gt;busnum-1) * 128) + 
(udev-&gt;devnum-1)));<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp; /* Increment the 
parent's count of unsuspended children */<BR>&nbsp;&nbsp;&nbsp;&nbsp; if 
(udev-&gt;parent)<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
usb_autoresume_device(udev-&gt;parent);<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp; /* 
Register the device.&nbsp; The device driver is 
responsible<BR>&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;* for adding the device files to 
sysfs and for configuring<BR>&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;* the 
device.<BR>&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;*/<BR>&nbsp;&nbsp;&nbsp;&nbsp; 
&nbsp;//注册usb_dev中内嵌的struct device<BR>&nbsp;&nbsp;&nbsp;&nbsp; err = 
device_add(&amp;udev-&gt;dev);<BR>&nbsp;&nbsp;&nbsp;&nbsp; if (err) 
{<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; dev_err(&amp;udev-&gt;dev, 
"can't device_add, error %d\n", 
err);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; goto 
fail;<BR>&nbsp;&nbsp;&nbsp;&nbsp; }<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp; /* 
Tell the world! */<BR>&nbsp;&nbsp;&nbsp;&nbsp; 
//输出一些该设备的信息<BR>&nbsp;&nbsp;&nbsp;&nbsp; 
announce_device(udev);<BR>&nbsp;&nbsp;&nbsp;&nbsp; return 
err;<BR>&nbsp;<BR>fail:<BR>&nbsp;&nbsp;&nbsp;&nbsp; usb_set_device_state(udev, 
USB_STATE_NOTATTACHED);<BR>&nbsp;&nbsp;&nbsp;&nbsp; return 
err;<BR>}<BR>这个代码的逻辑比较清淅.首先是usb_detect_quirks()函数,为个函数较简单,不打算进行详细分析,只是简单提一下.有些设备可能在设计存在一些问题.比如说,有的设备在Reset的时候会出现问题,或者在取string描述符的时候对buffer长度有要求.这样的设备都会在linux内核中形成一个链表,即usb_quirk_list.然后将设备的厂商ID,版本等信息与usb_quirk_list上的设备匹配.如果匹配到了,就在usb_dev添上相应的标识,不允许设备进行限制的功能.或者是设备驱动根据修改信息调整相关的操作.<BR>然后是usb_configure_device()函数.这个函数比较重要,跟踪进去分析一下&nbsp;:<BR>static 
int usb_configure_device(struct usb_device 
*udev)<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp; int 
err;<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp; //取得设备的配置<BR>&nbsp;&nbsp;&nbsp;&nbsp; 
if (udev-&gt;config == NULL) 
{<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; err = 
usb_get_configuration(udev);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
if (err &lt; 0) 
{<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
dev_err(&amp;udev-&gt;dev, "can't read configurations, error 
%d\n",<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
err);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
goto fail;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
}<BR>&nbsp;&nbsp;&nbsp;&nbsp; }<BR>&nbsp;&nbsp;&nbsp;&nbsp; 
//如果是无线设备<BR>&nbsp;&nbsp;&nbsp;&nbsp; if (udev-&gt;wusb == 1 &amp;&amp; 
udev-&gt;authorized == 0) {<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
udev-&gt;product = kstrdup("n/a (unauthorized)", 
GFP_KERNEL);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 

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