USB驱动程序的匹配分析

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2012-09-19 01:30:39| 分类：韦东山视频第二轮|举报|字号订阅

static struct usb_device_id usb_mouse_id_table [] = {

{ USB_INTERFACE_INFO(USB_INTERFACE_CLASS_HID, USB_INTERFACE_SUBCLASS_BOOT,

USB_INTERFACE_PROTOCOL_MOUSE) },

{ }

};

#define USB_INTERFACE_INFO(cl, sc, pr) \

.match_flags = USB_DEVICE_ID_MATCH_INT_INFO, \

.bInterfaceClass = (cl), \

.bInterfaceSubClass = (sc), \

.bInterfaceProtocol = (pr)

#define USB_DEVICE_ID_MATCH_INT_INFO \

(USB_DEVICE_ID_MATCH_INT_CLASS | \

USB_DEVICE_ID_MATCH_INT_SUBCLASS | \

USB_DEVICE_ID_MATCH_INT_PROTOCOL)

所以：

.match_flags = USB_DEVICE_ID_MATCH_INT_CLASS | USB_DEVICE_ID_MATCH_INT_SUBCLASS | USB_DEVICE_ID_MATCH_INT_PROTOCOL

.bInterfaceClass = 3

.bInterfaceSubClass = 1

.bInterfaceProtocol = 2

现在我们试着分析匹配函数：

//我们是usb接口

intf = to_usb_interface(dev);

usb_drv = to_usb_driver(drv);

usb_match_id(intf, usb_drv->id_table);

//id->bInterfaceClass不为空

usb_match_one_id(interface, id)

usb_match_device(dev, id)

我们好好看看这个函数：

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;

}

全都不匹配，于是继续往下走：

if ((id->match_flags & USB_DEVICE_ID_MATCH_INT_CLASS) &&

(id->bInterfaceClass != intf->desc.bInterfaceClass))

return 0;

if ((id->match_flags & USB_DEVICE_ID_MATCH_INT_SUBCLASS) &&

(id->bInterfaceSubClass != intf->desc.bInterfaceSubClass))

return 0;

if ((id->match_flags & USB_DEVICE_ID_MATCH_INT_PROTOCOL) &&

(id->bInterfaceProtocol != intf->desc.bInterfaceProtocol))

return 0;

在这几句中如果设备和驱动全部吻合的话，就匹配成功，返回1！

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