UAC麦克风音频控制的接口描述符

UAC麦克风包含一个音频控制接口，其以接口描述符为起始描述符。

描述符的关系如下：

• 接口描述符 //音频控制接口
  • 类特定音频流接口描述符
    • 输入终端描棕符
    • 输出终端描述符

接口描述符的内容详见：USB接口描述符 http://www.usbzh.com/article/detail-64.html

/* USB_DT_INTERFACE: Interface descriptor */
struct usb_interface_descriptor {
    __u8 bLength;
    __u8 bDescriptorType;
    __u8 bInterfaceNumber;
    __u8 bAlternateSetting;
    __u8 bNumEndpoints;
    __u8 bInterfaceClass;
    __u8 bInterfaceSubClass;
    __u8 bInterfaceProtocol;
    __u8 iInterface;
}
__attribute__((packed));#

数据结构配置如下：

define USB_DT_INTERFACE_SIZE 9

static struct usb_interface_descriptor uac1_interface_desc = {
    .bLength = USB_DT_INTERFACE_SIZE,
    .bDescriptorType = USB_DT_INTERFACE, 
    .bInterfaceNumber = 2, 
    .bNumEndpoints =0,
    .bInterfaceClass =USB_CLASS_AUDIO, 
    .bInterfaceSubClass =USB_SUBCLASS_AUDIOCONTROL, //
    .iInterface= 4
};

使用Free Device Monitoring Studio 抓取信息：

• descriptors[1] = “Interface Descriptor”
• bLength = 9
• bDescriptorType = USB_INTERFACE_DESCRIPTOR_TYPE (4)
• bInterfaceNumber = 0
• bAlternateSetting = 0
• bNumEndpoints = 0
• bInterfaceClass = UsbAudio (1)
• bInterfaceSubClass = 1
• bInterfaceProtocol = 0
• iInterface = 5