Linux-USB驱动笔记（七）--设备控制器(UDC)驱动

布满荆棘的人生 2022-09-11 06:21 708阅读 0赞

### Linux-USB驱动笔记（七）--设备控制器UDC驱动 ###

*  1、前言
 *  2、设备控制器(UDC)
 *   *  2.1、usb\_gadget -- USB从机设备
     *  2.2、usb\_gadget\_ops -- UDC操作函数
     *  2.3、usb\_ep -- 端点
     *  2.4、usb\_ep\_ops -- 端点操作函数
 *  3、总结如下

# 1、前言 #

在[Linux-USB驱动笔记（四）–USB整体框架][Linux-USB_USB]中有説到设备侧的设备控制器(UDC)，下面我们来具体看一下。

# 2、设备控制器(UDC) #

USB设备控制器(UDC)驱动指的是作为其他USB主机控制器的USB硬件设备上的底层控制器驱动。该硬件和驱动负责将一个USB设备依附于一个USB主机控制器上。

UDC驱动位于/drivers/usb/gadget目录下。

## 2.1、usb\_gadget – USB从机设备 ##

struct usb_gadget { 
      struct work_struct    work; 
      struct usb_udc      *udc; 
      /* readonly to gadget driver */
      const struct usb_gadget_ops  *ops; 
      struct usb_ep      *ep0; 
      struct list_head    ep_list;
      enum usb_device_speed    speed; 
      enum usb_device_speed    max_speed; 
      enum usb_device_state    state; 
      const char      *name;
      struct device      dev;
      unsigned      isoch_delay; 
      unsigned      out_epnum; 
      unsigned      in_epnum;
      unsigned      mA;  
      struct usb_otg_caps    *otg_caps; 
       //标志是否支持某些功能
      unsigned      sg_supported:1;
      unsigned      is_otg:1;
      unsigned      is_a_peripheral:1;
      unsigned      b_hnp_enable:1;
      unsigned      a_hnp_support:1;
      unsigned      a_alt_hnp_support:1;
      unsigned      hnp_polling_support:1;
      unsigned      host_request_flag:1;
      unsigned      quirk_ep_out_aligned_size:1;
      unsigned      quirk_altset_not_supp:1;
      unsigned      quirk_stall_not_supp:1;
      unsigned      quirk_zlp_not_supp:1;
      unsigned      quirk_avoids_skb_reserve:1;
      unsigned      is_selfpowered:1;
      unsigned      deactivated:1;
      unsigned      connected:1;
      unsigned      lpm_capable:1;
    };

<table> 
 <thead> 
  <tr> 
   <th>字段</th> 
   <th>含义</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>struct work_struct work;</td> 
   <td>sysfs_notify()使用的工作队列</td> 
  </tr> 
  <tr> 
   <td>struct usb_udc *udc;</td> 
   <td>usb设备控制器</td> 
  </tr> 
  <tr> 
   <td>const struct usb_gadget_ops *ops;</td> 
   <td>UDC操作函数</td> 
  </tr> 
  <tr> 
   <td>struct usb_ep *ep0;</td> 
   <td>端点0，用于驱动设置请求应答</td> 
  </tr> 
  <tr> 
   <td>struct list_head ep_list;</td> 
   <td>其他端口列表</td> 
  </tr> 
  <tr> 
   <td>enum usb_device_speed speed;</td> 
   <td>当前连接的USB主机速率</td> 
  </tr> 
  <tr> 
   <td>enum usb_device_speed max_speed;</td> 
   <td>UDC能处理的最大速率</td> 
  </tr> 
  <tr> 
   <td>enum usb_device_state state;</td> 
   <td>UDC状态</td> 
  </tr> 
  <tr> 
   <td>const char *name;</td> 
   <td>名称</td> 
  </tr> 
  <tr> 
   <td>struct device dev;</td> 
   <td>设备</td> 
  </tr> 
  <tr> 
   <td>unsigned isoch_delay;</td> 
   <td>设置等待请求</td> 
  </tr> 
  <tr> 
   <td>unsigned out_epnum;</td> 
   <td>最近使用的输出端点号</td> 
  </tr> 
  <tr> 
   <td>unsigned in_epnum;</td> 
   <td>最近使用的输入端点号</td> 
  </tr> 
  <tr> 
   <td>unsigned mA;</td> 
   <td>最近设置的mA值</td> 
  </tr> 
  <tr> 
   <td>struct usb_otg_caps *otg_caps;</td> 
   <td>OTG功能</td> 
  </tr> 
 </tbody> 
</table>

## 2.2、usb\_gadget\_ops – UDC操作函数 ##

struct usb_gadget_ops { 
      int  (*get_frame)(struct usb_gadget *);
      int  (*wakeup)(struct usb_gadget *);
      int  (*set_selfpowered) (struct usb_gadget *, int is_selfpowered);
      int  (*vbus_session) (struct usb_gadget *, int is_active);
      int  (*vbus_draw) (struct usb_gadget *, unsigned mA);
      int  (*pullup) (struct usb_gadget *, int is_on);
      int  (*ioctl)(struct usb_gadget *,
            unsigned code, unsigned long param);
      void  (*get_config_params)(struct usb_dcd_config_params *);
      int  (*udc_start)(struct usb_gadget *,
          struct usb_gadget_driver *);
      int  (*udc_stop)(struct usb_gadget *);
      void  (*udc_set_speed)(struct usb_gadget *, enum usb_device_speed);
      struct usb_ep *(*match_ep)(struct usb_gadget *,
          struct usb_endpoint_descriptor *,
          struct usb_ss_ep_comp_descriptor *);
    };

以面的操作函数不涉及端点操作。

## 2.3、usb\_ep – 端点 ##

struct usb_ep { 
      void      *driver_data;
    
      const char    *name;
      const struct usb_ep_ops  *ops; 
      struct list_head  ep_list;
      struct usb_ep_caps  caps;
      bool      claimed;
      bool      enabled;
      unsigned    maxpacket:16;
      unsigned    maxpacket_limit:16;
      unsigned    max_streams:16;
      unsigned    mult:2;
      unsigned    maxburst:5;
      u8      address;
      const struct usb_endpoint_descriptor  *desc; 
      const struct usb_ss_ep_comp_descriptor  *comp_desc;
    };

重要字段及其含义如下：

<table> 
 <thead> 
  <tr> 
   <th>字段</th> 
   <th>含义</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>const struct usb_ep_ops *ops</td> 
   <td>端点操作函数集</td> 
  </tr> 
  <tr> 
   <td>const struct usb_endpoint_descriptor *desc</td> 
   <td>端点描述符</td> 
  </tr> 
 </tbody> 
</table>

## 2.4、usb\_ep\_ops – 端点操作函数 ##

struct usb_ep_ops { 
      int (*enable) (struct usb_ep *ep,
        const struct usb_endpoint_descriptor *desc);
      int (*disable) (struct usb_ep *ep);
      void (*dispose) (struct usb_ep *ep);
    
      struct usb_request *(*alloc_request) (struct usb_ep *ep,
        gfp_t gfp_flags);
      void (*free_request) (struct usb_ep *ep, struct usb_request *req);
    
      int (*queue) (struct usb_ep *ep, struct usb_request *req,
        gfp_t gfp_flags);
      int (*dequeue) (struct usb_ep *ep, struct usb_request *req);
    
      int (*set_halt) (struct usb_ep *ep, int value);
      int (*set_wedge) (struct usb_ep *ep);
    
      int (*fifo_status) (struct usb_ep *ep);
      void (*fifo_flush) (struct usb_ep *ep);
    };

# 3、总结如下 #

*  1、usb\_gadget表示一个从机设备(UDC + 端点)，它包含一些端点(包括端点0和其他端点)。所以它有一个端点列表成员ep\_list， 初始化过程中会将所有需要的端点放到该链表中。
 *  2、 usb\_gadget\_ops主要用来操作UDC。
 *  3、 usb\_ep表示一个端点，每个端点都有自己的操作函数usb\_ep\_ops。
 *  4、 usb\_ep\_ops主要用来操作端点。

[Linux-USB_USB]: https://blog.csdn.net/weixin_45309916/article/details/119979199