Re: [patch 03/13] input: make input a multi-object module

[Andrew Morton <akpm@osdl.org>]

Anssi Hannula <anssi.hannula@gmail.com> wrote:
>
> Andrew Morton wrote:
> > Anssi Hannula <anssi.hannula@gmail.com> wrote:
> > 
> >>
> >>>>>It would be much nicer all round if we could avoid renaming this file.
> >>>>
> >>>>Indeed... There are these 4 options as far as I see:
> >>>>
> >>>>1. Do this rename
> >>>>2. Put all the code in input-ff.c to input.c
> >>>>3. Make the input-ff a separate bool "module" and add
> >>>>EXPORT_SYMBOL_GPL() for input_ff_event() which is currently the only
> >>>>function in input-ff.c that is called from input.c
> >>>>4. Rename the input "module" to something else, it doesn't matter so
> >>>>much as almost everybody builds it as built-in anyway.
> >>>>
> >>>>WDYT is the best one?
> >>>
> >>>
> >>>I still don't know what problem you're trying to solve so I cannot say.
> >>
> >>Maybe you know now.
> > 
> > 
> > yup, thanks.
> > 
> > I'd have thought that 3) is the path of least resistance.
> > 
> > But it does require that input.c "knows" that input-ff.c was included in
> > the build, which is not a thing we like to do.
> 
> Well, it's going to be included as built-in and can't be built as a
> module at all, so I think it's okay for us to do so?

If that's the case then no EXPORT_SYMBOL_GPL() is needed - we just link the
the two .o files together, link the result into vmlinux?

> > Why should things in input.c call into input-ff.c, btw?  The way we
> > normally would handle that is to add a register_something() API to input.c
> > and input-ff.c would insert its callback via that interface.
> 
> Yes, we could easily add a callback to e.g. struct input_dev, but is
> that really preferred if the input-ff.c is built-in?

Nope, not if they're as tightly-coupled as that.

However it still might not be _appropriate_ for the input core code to call
into the force-feedback code in this manner.  It certainly sounds unusual.