centos man page for usb_interface_id

USB_INTERFACE_ID(9)					      Kernel Mode Gadget API					       USB_INTERFACE_ID(9)

NAME
       usb_interface_id - allocate an unused interface ID

SYNOPSIS
       int usb_interface_id(struct usb_configuration * config, struct usb_function * function);

ARGUMENTS
       config
	   configuration associated with the interface

       function
	   function handling the interface

CONTEXT
       single threaded during gadget setup

DESCRIPTION
       usb_interface_id is called from usb_function.bind callbacks to allocate new interface IDs. The function driver will then store that ID in
       interface, association, CDC union, and other descriptors. It will also handle any control requests targeted at that interface, particularly
       changing its altsetting via set_alt. There may also be class-specific or vendor-specific requests to handle.

       All interface identifier should be allocated using this routine, to ensure that for example different functions don't wrongly assign
       different meanings to the same identifier. Note that since interface identifiers are configuration-specific, functions used in more than
       one configuration (or more than once in a given configuration) need multiple versions of the relevant descriptors.

       Returns the interface ID which was allocated; or -ENODEV if no more interface IDs can be allocated.

AUTHOR
       David Brownell <dbrownell@users.sourceforge.net>
	   Author.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014						       USB_INTERFACE_ID(9)