1、前言
在Linux-USB驱动笔记（四）–USB整体框架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;
};
| 字段 | 含义 |
|---|---|
| struct work_struct work; | sysfs_notify()使用的工作队列 |
| struct usb_udc *udc; | usb设备控制器 |
| const struct usb_gadget_ops *ops; | UDC操作函数 |
| struct usb_ep *ep0; | 端点0，用于驱动设置请求应答 |
| struct list_head ep_list; | 其他端口列表 |
| enum usb_device_speed speed; | 当前连接的USB主机速率 |
| enum usb_device_speed max_speed; | UDC能处理的最大速率 |
| enum usb_device_state state; | UDC状态 |
| const char *name; | 名称 |
| struct device dev; | 设备 |
| unsigned isoch_delay; | 设置等待请求 |
| unsigned out_epnum; | 最近使用的输出端点号 |
| unsigned in_epnum; | 最近使用的输入端点号 |
| unsigned mA; | 最近设置的mA值 |
| struct usb_otg_caps *otg_caps; | OTG功能 |
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：
| 字段 | 含义 |
|---|---|
| const struct usb_ep_ops *ops | 端点操作函数集 |
| const struct usb_endpoint_descriptor *desc | 端点描述符 |
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。