Data: 07/04/2018
De: Deltaaqbatp
0x00000002, DriverService Listing 16-1: An INF file for a generic USB virtual COM port using the CDC drivers Sheet 1 of 2 . 357 Chapter 16 DriverService DisplayName=%SERVICE% ServiceType=1 StartType=3 ErrorControl=1 ServiceBinary=%12%\usbser.sys Strings LAKEVIEW="Lakeview Research LLC MFGItlAME="Lakeview Research LLC DESCRIPTION='USB COM Port" SERVICE='USB COM-port Driver" Listing 16-1: An INF file for a generic USB virtual COM port using the CDC drivers Sheet 2 of 2 . codes in the interface descriptors. When a single function uses multiple interfaces, a device can use an interface association descriptor or a class-specific method to identify the interfaces associated with a function. CDC Differences CDC differs from other classes because it defines a code for bDeviceClass 02h in the device descriptor. In theory, this difference shouldn’t present a problem for composite devices. The union functional descriptor defines which interfaces belong to the CDC function, and the host can assume that any additional interface descriptors belong to independent functions. In practice, however, the drivers in earlier Windows editions aren’t always capable of loading the drivers correctly for composite devices that contain CDC functions. Interface Association Descriptor Under Windows Vista, a composite device with a CDC virtual COM-port function can use an interface association descriptor IAD to identify the interfaces that belong to the CDC function. Windows can then identify and load the correct drivers for all of the composite device’s functions. Figure 16-2 shows the descriptors for an example composite device of this type. Table 16-7 shows the contents of the IAD as defined in the USB 2.0 engineering change notice ECN Interface Association Descriptors. To inform the host that the device uses an IAD, the device descriptor should use the values in Table 358 Using Generic USB Controllers Figure 16-2: A composite device that contains a CDC function and a HID function prom-electric.ru
