Gadget Framework 代码分析(二) --- zero.c

排版有些问题，请参考http://blog.csdn.net/zkami

struct zero_dev {
         spinlock_t  lock;
         struct usb_gadget *gadget; //代表一个gadget设备
         struct usb_request *req;  /* for control responses */

 /* when configured, we have one of two configs:
  * - source data (in to host) and sink it (out from host)
  * - or loop it back (out from host back in to host)
  */
         u8   config;
         struct usb_ep  *in_ep, *out_ep;

 /* autoresume timer */
         struct timer_list resume;
};

以下定义了这个gadget设备的device, configure, interface...
其中的struct usb_device_descriptor，usb_config_descriptor，usb_otg_descriptor
usb_interface_descriptor，usb_endpoint_descriptor，usb_descriptor_header
定义在ch9.h，structure中的各字段与Spec相对应,忘记了同学最好复习一下USB2.0 Spec的第9章吧。  
static struct usb_device_descriptor  device_desc      ------- device
static struct usb_config_descriptor  source_sink_config    
static struct usb_config_descriptor  loopback_config     ---device中包括2个config
static struct usb_otg_descriptor     otg_descriptor  --- OTG
static struct usb_interface_descriptor  source_sink_intf
static struct usb_interface_descriptor  loopback_intf  ---每个config包括2个interface
static struct usb_endpoint_descriptor   fs_source_desc
static struct usb_endpoint_descriptor   fs_sink_desc  ---2个full speed bull 端点
static struct usb_descriptor_header *fs_source_sink_function []
static struct usb_descriptor_header *fs_loopback_function []
static struct usb_endpoint_descriptor  hs_source_desc
static struct usb_endpoint_descriptor  hs_sink_desc ---2个high speed bulk 端点
static struct usb_qualifier_descriptor  dev_qualifier
static struct usb_descriptor_header *hs_source_sink_function []
static struct usb_descriptor_header *hs_loopback_function []

static struct usb_gadget_driver zero_driver = {//这个gadget设备的driver
 ...
 .function = (char *) longname,
 .bind  = zero_bind,
 .unbind  = __exit_p(zero_unbind),
 .setup  = zero_setup,  //设备对host端setup()的response
 .disconnect = zero_disconnect,
 .suspend = zero_suspend,
 .resume  = zero_resume,
  ...
};

//处理ep0的控制请求
static int
zero_setup (struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
{
         struct zero_dev  *dev = get_gadget_data (gadget);
         struct usb_request *req = dev->req;
         u16 w_index = le16_to_cpu(ctrl->wIndex); //制定一个ep或interface
         u16 w_value = le16_to_cpu(ctrl->wValue); //req的特定参数
         u16 w_length = le16_to_cpu(ctrl->wLength); //data阶段的data长度
根据ctrl->bRequest(请求的类型):
         USB_REQ_GET_DESCRIPTOR:
              根据w_value>>8来判断要get的descriptor类型:
              USB_DT_DEVICE:  把&device_desc的数据拷贝到req->buf
              USB_DT_DEVICE_QUALIFIER: 把&device_qualifier的数据拷贝到req->buf
              USB_DT_OTHER_SPEED_CONFIG:
              USB_DT_CONFIG:  把该config下的所有interface, ep都拷贝到req->buf
              USB_DT_STRING:
         USB_REQ_SET_CONFIGURATION:
              zero_set_config(dev, w_value);  //w_value就是要set的config的value,即dev->config
         USB_REQ_GET_CONFIGURATION:
              *(u8 *)req->buf = dev->config; //返回当前config的value
         USB_REQ_SET_INTERFACE:
              zero_reset_config (dev);
              zero_set_config(dev, config);
         USB_REQ_GET_INTERFACE:
 ...
最后把ep的request放到queue中去,作为对host的应答
         value = usb_ep_queue (gadget->ep0, req, GFP_ATOMIC);
}