> >> This is probably a very stupid question, but... what I wonder is how to
> >> get a "struct device foodev" that way,
> >
> > you can't.  you don't need to do so, if you make it really opaque.
> 
> What does "opaque" mean? I wonder where all those things come from that 
> these pointers point to... X-)
> 
> (Yes, I'm aware that this is a very newbie question... I fetched myself a 
> bloody nose again trying to dig into our kernel, and still have no real 
> idea where to start; I'm aware that this is probably not the best point?)

it isn't kernel-specific at all.
eg. you don't need to know members or size of FILE when using stdio.

YAMAMOTO Takashi