UAC麦克风音频流接口描述符

UAC麦克风音频流接口描述符使用普通用USB接口描述符结构，该描述符是音频流描述符集合的开始。

UAC音频流描述符的组织结构如下图：

UAC麦克风音频流接口描述符的数据配置如下：

接口描述符的各字段的解释详见：USB接口描述符 http://www.usbzh.com/article/detail-64.html

源代码如下：

： /* 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));#
define USB_DT_INTERFACE_SIZE9
/* B.4.1  Standard AS Interface Descriptor */
static struct usb_interface_descriptor microphone_as_interface_alt_0_desc = {.bLength = USB_DT_INTERFACE_SIZE,
    .bDescriptorType = USB_DT_INTERFACE,
    .bAlternateSetting = 0,
    .bNumEndpoints = 0,
    .bInterfaceClass = USB_CLASS_AUDIO,
    .bInterfaceSubClass = USB_SUBCLASS_AUDIOSTREAMING,
};
static struct usb_interface_descriptor microphone_as_interface_alt_1_desc = {.bLength = USB_DT_INTERFACE_SIZE,
    .bDescriptorType = USB_DT_INTERFACE,
    .bAlternateSetting = 1,
    .bNumEndpoints = 1,
    .bInterfaceClass = USB_CLASS_AUDIO,
    .bInterfaceSubClass = USB_SUBCLASS_AUDIOSTREAMING,
};

模拟设备信息Free Device Monitoring Studio 抓取
UAC音频采用同步传输，故需要2个接口描述符，第二个为第一个描述符的转换接口描述符即备用接口描述符。

• descriptors[5] = “Interface Descriptor”
• bLength = 9
• bDescriptorType = USB_INTERFACE_DESCRIPTOR_TYPE (4)
• bInterfaceNumber = 1
• bAlternateSetting = 0
• bNumEndpoints = 0
• bInterfaceClass = UsbAudio (1)
• bInterfaceSubClass = 2
• bInterfaceProtocol = 0
• iInterface = 0

转换接口描述符：

• descriptors[6] = “Interface Descriptor”
• bLength = 9
• bDescriptorType = USB_INTERFACE_DESCRIPTOR_TYPE (4)
• bInterfaceNumber = 1
• bAlternateSetting = 1
• bNumEndpoints = 1
• bInterfaceClass = UsbAudio (1)
• bInterfaceSubClass = 2
• bInterfaceProtocol = 0
• iInterface = 0