📄 linux设备驱动之usb主机控制器驱动分析-(3)_linux技术文章_linux_操作系统3.htm
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hcd_buffer_destroy(hcd);<BR> return
retval;<BR>}<BR> <BR>经过前面的段式分析,我们对这个函数的流程有了一定的了解.其中有几个函数特别列出,分析如下:<BR>2.1:usb_alloc_dev()的操作<BR>之所以要特别列出分析,是因为这个函数中有很重要的赋值操作.代码如下:<BR>struct
usb_device *usb_alloc_dev(struct usb_device
*parent,<BR>
struct usb_bus *bus, unsigned port1)<BR>{<BR>
struct usb_device *dev;<BR>
//从bus结构,求得usb_hcd<BR> struct usb_hcd *usb_hcd =
container_of(bus, struct usb_hcd, self);<BR> unsigned
root_hub = 0;<BR> <BR> dev = kzalloc(sizeof(*dev),
GFP_KERNEL);<BR> if
(!dev)<BR> return
NULL;<BR> <BR>
//增加hcd的引用计数<BR> if (!usb_get_hcd(bus_to_hcd(bus)))
{<BR>
kfree(dev);<BR> return
NULL;<BR> }<BR> <BR>
//usb_device,内嵌有struct device结构,对这个结构进行初始化<BR>
device_initialize(&dev->dev);<BR> dev->dev.bus
= &usb_bus_type;<BR> dev->dev.type =
&usb_device_type;<BR> dev->dev.dma_mask =
bus->controller->dma_mask;<BR>
set_dev_node(&dev->dev,
dev_to_node(bus->controller));<BR>
//将dev的初始状态置为USB_STATE_ATTACHED.妻示已经连接上了<BR>
dev->state = USB_STATE_ATTACHED;<BR>
atomic_set(&dev->urbnum, 0);<BR> <BR>
//初始化设备的端点0<BR>
INIT_LIST_HEAD(&dev->ep0.urb_list);<BR>
dev->ep0.desc.bLength = USB_DT_ENDPOINT_SIZE;<BR>
dev->ep0.desc.bDescriptorType = USB_DT_ENDPOINT;<BR>
/* ep0 maxpacket comes later, from device descriptor
*/<BR> usb_enable_endpoint(dev,
&dev->ep0);<BR> dev->can_submit =
1;<BR> <BR> /* Save readable and stable topology
id, distinguishing devices<BR> * by location for
diagnostics, tools, driver model, etc. The<BR>
* string is a path along hub ports, from the root. Each
device's<BR> * dev->devpath will be stable
until USB is re-cabled, and hubs<BR> * are often
labeled with these port numbers. The bus_id
isn't<BR> * as stable: bus->busnum
changes easily from modprobe order,<BR> * cardbus
or pci hotplugging, and so on.<BR>
*/<BR> //如果没有父结点,也即该设备是root
hub.usb_device内嵌的dev的父结点指向它的控制器<BR> if
(unlikely(!parent)) {<BR>
dev->devpath[0] =
'0';<BR> <BR>
dev->dev.parent =
bus->controller;<BR>
sprintf(&dev->dev.bus_id[0], "usb%d",
bus->busnum);<BR> root_hub =
1;<BR> } else
{<BR> <BR>
//如果有父结点,就指向其父结点<BR> /* match
any labeling on the hubs; it's one-based
*/<BR> if (parent->devpath[0]
==
'0')<BR>
snprintf(dev->devpath, sizeof
dev->devpath,<BR>
"%d", port1);<BR>
else<BR>
snprintf(dev->devpath, sizeof
dev->devpath,<BR>
"%s.%d", parent->devpath,</P>
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