[PATCH libinput] evdev: accept accelerometers if they are tagged as other devices too

[Peter Hutterer]

On Tue, Aug 29, 2017 at 11:03:59AM -0700, Roderick Colenbrander wrote:
> On Sat, Aug 26, 2017 at 2:18 AM, Peter Hutterer
> <peter.hutterer at who-t.net> wrote:
> > On 26/08/2017 06:52 , Roderick Colenbrander wrote:
> >>
> >> Hi Peter,
> >>
> >> I'm not too familiar with this code, but does this prevent usage of
> >> accelerometer axes in libevdev for pure accelerometer devices as in
> >> devices setting INPUT_PROP_ACCELEROMETER and not providing buttons or
> >> other axes? As you are aware we are quite interested in in dualshock 3
> >> / 4 gamepads and we have a pure accelerometer composite device. It
> >> would be nice to be able to get the data out through libevdev as well.
> >> If my understanding is correct this prevents this? As I said I'm not
> >> too familiar with the code base.
> >
> >
> > Note that this patch is just for libinput, not libevdev. libevdev still
> > doesn't care what a device is and merely forwards everything. libinput
> > doesn't do joysticks though and uses libevdev to filter the events. If you
> > have your own libevdev context (and you will, because libinput doesn't
> > expose its libevdev context) then this doesn't apply to you and you still
> > get all events. And afaict you're not using libinput, right?
> >
> > Cheers,
> >   Peter
> >
> 
> Correct, we mostly use libevdev right now, but we are exploring to use
> libinput, but as you said libinput doesn't do joysticks. The bigger
> question is whether it should I guess. Just for background, the main
> use case we are interested in controlling a whole desktop UX through a
> gamepad.

tbh, I'm not sure this is really something that's generic enough to warrant
putting it into libinput. There are some desktops that should be used like
that (the playstation one for example) but those are special cases and they
need to be more aware of gamepads and joysticks than libinput can ever be.
libinput doesn't really provide a benefit here, at least not for the
gamepads.

Cheers,
   Peter