EXT: Multiple touchscreen environment with Weston

[Pekka Paalanen]

On Fri, 21 Jun 2019 07:40:12 +0000
Theo BUENO <theo.bueno at actia.fr> wrote:

> Yes, unfortunately it is unlikely that open-source drivers with DRM
> support will happen anytime soon for my use-case.
> 
> Do you have an idea of the amount of work required to make multi-seat
> and touchscreen binding work on the fbdev backend ?

Hi Theo,

I believe the only thing you need is to have the fbdev backend
actually provide more than one output and name each uniquely.
Everything about the input side, e.g. WL_OUTPUT for touch input
devices, is in code shared with the DRM-backend, so I think it
should just work.

My memory is hazy, but you might even find some patches in the
mailing list archives making fbdev-backend open all fbdev devices
instead of just one. I forget if that was just talk or if there
actually were patches.

That is, if you mean one physical seat with multiple outputs. If
you mean multiple physical seats one output each, then it's
possible you don't need code changes.

> More generally what
> are the plans for this backend in future versions of Weston ?

The plan is to remove it. It was already suggested around the
previous release, but one user wished for it to stay, so it stayed.
The maintenance burden on the fbdev-backend is low, so there
is no hurry in removing it, but further development of it is
discougared. If you wrote patches for it, they might not get merged.

> I am well
> aware that fbdev is obsolete and should be replaced by DRM but a lot of
> legacy hardware will never see that change.

Indeed, yet writing a DRM driver providing the same feature set as
an fbdev device should be very easy today, thanks to all the
helpers aimed for that exact use case in the kernel DRM. If you
want to know more about this, reach out on dri-devel mailing list
or ask e.g. Daniel Vetter for pointers.

Mind that I'm not talking about EGL on fbdev. That bit of code was
removed from Weston upstream a long time ago. If you need GPU
acceleration and a FOSS driver project does not exist already then
there is no easy way forward.


Thanks,
pq
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