[movitz-devel] Re: Bits and pieces

[Frode Vatvedt Fjeld]

Luke Gorrie <luke at bluetail.com> writes:

> Anyway. I've got a working compiler from Erlang to Lisp and I've
> used it to write a "hello world" ErlangOS. But it currently only
> handles the sequential subset of Erlang and that's not going to
> impress my friends. So I need to add support for concurrency.

Yes, this is something I'm hoping to be able to do in the
not-too-distant future too (a few months).

> I think a nice way to do this would be to have Lisp-level coroutines
> as the building block. It looks like this is mostly written in
> Movitz but I'm not sure if it's finished (couldn't figure out how to
> use it).  I'm looking at functions like COPY-CONTROL-STACK,
> CLONE-RUN-TIME-CONTEXT, and SWITCH-TO-CONTEXT.
>
> Is that stuff usable? If not, what needs to be done?

It's not usabel as-is. Copy-control-stack I wrote quite recently, as a
debugging tool actually, but it'll clearly become a concurrency
primitive also. Clone-run-time-context and switch-to-context I wrote
quite a while ago trying to get some threads going, but I stopped that
work for some reasone I don't remember. This means they are incomplete
and possibly a bit outdated wrt. the changes in the run-time-context
since then.

If you want to try and make this stuff work properly for threads or
coroutines or whatever, please do :) It probably requires you to
figure out how the bits and pices of the run-time-context and
associated structures fit together, but there's nothing really
complicated in there, I believe. I'll of course answer any questions
here or on #lisp.

> Ideally I would like coroutines to have variable-size stacks
> (growing and shrinking on demand), but that's not so important -
> I'll take anything I can get :-)

This should also be no problem to implement, and it's really unrelated
to the concurrency stuff. Well, one issue is from where does one
allocate the stack.. When there's one thread like today there's no
such issue, but later one there's got to be some better global memory
management.

> I'd also like to do some VGA hacks. Is there any example code?

There's losp/x86-pc/{vga,textmode}.lisp. The stuff in vga.lisp mostly
just fiddles with the textmode registers, but I guess the graphcis
stuff isn't much different.


Did everyone try (x86-pc:set-textmode +vga-state-90x60+) yet, or
+vga-state-40x25+ for the visually challenged? :)

Luke: I suspect (setf vga-state) is what needs to be slightly improved
(or even just give it the right parameters) to have graphics.

Oh, and isn't it possible to have the VGA textmode be 132 wide? Does
anyone know how to figure out e.g. +vga-state-132x60+ ?

-- 
Frode Vatvedt Fjeld