Input driver on 1.15.1 vs. 1.19.6

[Peter Hutterer]

On Thu, Oct 10, 2019 at 02:27:36AM +0000, Software Orchestration wrote:
> 
>   Alan Coopersmith <alan.coopersmith at oracle.com> wrote: > I have no idea who decided what releases to list there as supported, but X.Org
> > certainly isn't supporting all those releases upstream - though some downstream
> > distros may be doing so. X.Org itself is mainly maintaining the 1.20 series now:
> > https://gitlab.freedesktop.org/xorg/xserver/-/branches
> 
> I figured you were on this list...thanks for replying.
> My question is first trying to understand what I need to get this working on Ubuntu 18.04. Currently the Xorg server is 1.19.6 and I don't see that changing until 20.04. They will still have 1 more year on 18.04 as it's a 5 year LTS I believe.
> First I'm just trying to understand if interfaces changed, if legacy works at all, or what the differences are so I can isolate the problem and fix it.
> If an input driver was brought up to 1.19.x, would it be likely to run on 1.20.x?
> I think I could get 1.20 on Ubuntu 19.08, do you know if that's the case?

I'd argue that any input driver that worked in the past should still work
with current X servers, provided that you switch the SIGIO bits over to
handle input threads instead.

There are very few features that have truly been removed from input drivers
such as access to the screen dimensions etc. Can't remember when this happen
but my gut feeling is that if it worked on 1.15 it'll probably work on
1.19.

Cheers,
   Peter

> > There certainly have been driver API/ABI updates between the two:
> > https://www.x.org/wiki/XorgModuleABIVersions/
> I saw in 1.16.x there was quite a bit of input changes, but wasn't sure how the APIs are supported.
> There seems to be a fairly large grey area.
> On top of all that, the was hacked together from another serial device, so as you might imagine it's a pretty big mess...but the good thing is there's only about 1000 LOC for the current driver.
> I'm trying to figure out if I might be better off starting off with a current serial input device as a template and merge their code to get a working driver on 18.04. 
> 
> > > The code uses xf86ReadSerial() and xf86WriteSerial().
> >
> > Doesn't look like there's been a whole lot of change there in recent years:
> > https://gitlab.freedesktop.org/xorg/xserver/commits/master/hw/xfree86/os-support/shared/posix_tty.c
> 
> That's good, maybe my chance is pretty good on 18.04.
> 
> > Examples of input device drivers for Xorg?
> > 
> > https://gitlab.freedesktop.org/xorg/driver?filter=input> ...
> > XFREE86_V3 code is almost 20 years out of date now, while XFREE86_V4 code would
> > be closer to 15 years out of date.
> Thanks for that link, looks like the xf86-input-libinput might be good for me to look at.
> I wish I wasn't doing this, but I really needed the work...so...I'd like to try and solve this for my client. Running on an old Atom processor that is at least 10+ years old, limited on memory, etc...I've seen this movie a number of times over the years...it's kind of like a rerun...:-/
> 
> Alan
>   

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