
If a suitable driver is not found, the device might not have a driver loaded. The Plug and Play manager tries to find a driver.
If your device specifies class code 02 but a subclass code value other than 02, Usbser.sys does not load automatically. With this approach, you are not required to distribute INF files for your device because the system uses Usbser.inf.
For more information, see USB communications device class.
If you want to load Usbser.sys automatically, set the class code to 02 and subclass code to 02 in the Device Descriptor. The driver is loaded based on a compatible ID match similar to other USB device class drivers included in Windows. You do not need to write your own INF to reference the driver. If your device belongs to the communications and CDC control device class, Usbser.sys is loaded automatically.
Starting in Windows 10, Usbser.inf was added to the %Systemroot%\INF directory, which loads Usbser.sys as the functional device object (FDO) in the device stack. For the list of USB device class driver included in Windows, see USB device class drivers included in Windows. If they are not installed automatically, contact the device manufacturer. If you trying to install a USB device class driver included in Windows, you do not need to download the driver.