This patch provides an infrastructure to register & unregister a USB function. This allows to turn a function into a module and avoid the '#include "f_.*.c"' magic and we get a clear API / cut between the bare gadget and its functions. The concept is simple: Each function defines the DECLARE_USB_FUNCTION_INIT macro whith an unique name of the function and two allocation functions. - one to create an "instance". The instance holds the current configuration set. In case there are two usb_configudations with one function there will be one instance and two usb_functions - one to create an "function" from the instance. The name of the instance is used to automaticaly load the module if it the instance is not yet available. The usb_function callbacks are slightly modified and extended: - usb_get_function() creates a struct usb_function inclunding all pointers (bind, unbind,…). It uses the "instance" to map its configuration. So we can have _two_ struct usb_function, one for each usb_configuration. - ->unbind() Since the struct usb_function was not allocated in ->bind() it should not kfree()d here. This function should only reverse what happens in ->bind() that is request cleanup and the cleanup of allocated descriptors. - ->free_func() a simple kfree() of the struct usb_function Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Felipe Balbi <balbi@ti.com>