USB Host CDC Attach Listeners Number 

The USB CDC Host Client Driver provides attach notification to listeners who have registered with the client driver via the USB_HOST_CDC_AttachEventHandlerSet() function. The USB_HOST_CDC_ATTACH_LISTENERS_NUMBER configuration constant defines the maximum number of event handlers that can be set. This number should be set to equal the number of entities that interested in knowing when a CDC device is attached.

#define USB_HOST_CDC_ATTACH_LISTENERS_NUMBER 

None.