> In kern/kern_subr.c, a function "finddevice" enables to retrieve a 
> device information by its name, however, lkm can't call the function.

... because finddevice() is static. But maybe net/if.c:ifunit() might
be more useful to you as you mentioned you'll work with network
interfaces (finddevice() gives you 'struct device *', ifunit() gives
'struct ifnet *').

	Regards,
		-- Jachym Holecek