UAC麦克风输入终端描述符

输入终端描述符在拓扑结构中表示数据的来源端。
该UAC麦克风输入终端描述符的数据配置如下：

关于输入终端描述符的解释见:http://www.usbzh.com/article/detail-180.html

输入终端描述符结构体和数据初始化代码如下：

/* 4.3.2.1 Input Terminal Descriptor */
struct uac_input_terminal_descriptor {
    __u8 bLength; /* in bytes: 12 */
    __u8 bDescriptorType; /* CS_INTERFACE descriptor type */
    __u8 bDescriptorSubtype; /* INPUT_TERMINAL descriptor subtype */
    __u8 bTerminalID; /* Constant uniquely terminal ID */
    __le16 wTerminalType; /* USB Audio Terminal Types */
    __u8 bAssocTerminal; /* ID of the Output Terminal associated */
    __u8 bNrChannels; /* Number of logical output channels */
    __le16 wChannelConfig;
    __u8 iChannelNames;
    __u8 iTerminal;
}
__attribute__((packed));
static struct uac_input_terminal_descriptor microphone_input_terminal_desc = {.bLength = UAC_DT_INPUT_TERMINAL_SIZE,
    .bDescriptorType = USB_DT_CS_INTERFACE,
    .bDescriptorSubtype = UAC_INPUT_TERMINAL,
    .bTerminalID = MICROPHONE_INPUT_TERMINAL_ID,
    .wTerminalType = UAC_INPUT_TERMINAL_MICROPHONE,
    .bAssocTerminal = MICROPHONE_OUTPUT_TERMINAL_ID,
    .bNrChannels = 1,
    .wChannelConfig = 0x3,
};

通过Free Device Monitoring Studio抓取该设备的输入终端描述符信息：

• descriptors[3] = “Class-Specific Interface Descriptor”
• bLength = 12
• bDescriptorType = CS_INTERFACE (36)
• bDescriptorSubtype = 2
• ac_interface =
• input_terminal =
• bTerminalID = 1
• wTerminalType = 513
• bAssocTerminal = 2
• bCSourceID = 1
• bNrChannels = 3
• bmChannelConfig = 150994944
• iChannelNames = 36
• terminal_control =
• terminal =
• CopyProtect = 3
• ConnectorControl = 0
• OverloadControl = 0
• ClusterControl = 0
• UnderflowControl = 2
• OverflowControl = 0
• Reserved = 0
• bmControls = 0000001000000011
• iTerminal = 1