框架

usb 驱动是基于usb core 的，设备插上之后，host 层自然会进行识别，设备驱动通过core层的接口操作设备，而不用直接面对usb硬件。对于应用层需要封装成一个usb 的设备。

驱动是基于urb 数据进行操作的。

 49 static void usb_mouse_irq(struct urb *urb)
 50 {   
 51     struct usb_mouse *mouse = urb->context;
 52     signed char *data = mouse->data;
 53     struct input_dev *dev = mouse->dev;
 54     int status;
 55     
 56     switch (urb->status) {
 57     case 0:         /* success */
 58         break;
 59     case -ECONNRESET:   /* unlink */
 60     case -ENOENT:
 61     case -ESHUTDOWN:
 62         return;
 63     /* -EPIPE:  should clear the halt */
 64     default:        /* error */
 65         goto resubmit;
 66     }
 67     
 68     input_report_key(dev, BTN_LEFT,   data[0] & 0x01);
 69     input_report_key(dev, BTN_RIGHT,  data[0] & 0x02);
 70     input_report_key(dev, BTN_MIDDLE, data[0] & 0x04);
 71     input_report_key(dev, BTN_SIDE,   data[0] & 0x08);
 72     input_report_key(dev, BTN_EXTRA,  data[0] & 0x10);
 73     
 74     input_report_rel(dev, REL_X,     data[1]);
 75     input_report_rel(dev, REL_Y,     data[2]);
 76     input_report_rel(dev, REL_WHEEL, data[3]);
 77     
 78     input_sync(dev);
... 
}
106 static int usb_mouse_probe(struct usb_interface *intf, const struct usb_device_id *id)
107 {
111     struct usb_mouse *mouse;
112     struct input_dev *input_dev;
137     mouse->irq = usb_alloc_urb(0, GFP_KERNEL);
138     if (!mouse->irq)
139         goto fail2;
175     input_set_drvdata(input_dev, mouse);
180     usb_fill_int_urb(mouse->irq, dev, pipe, mouse->data,
181              (maxp > 8 ? 8 : maxp),
182              usb_mouse_irq, mouse, endpoint->bInterval);
186     error = input_register_device(mouse->dev);
187     if (error)
188         goto fail3;
...
}