bug#40538: installer: Support uvesafb to install on machines without KMS.

[Bengt Richter]

On +2020-04-12 08:37:02 +0200, Bengt Richter wrote:
> Hi Ludo, Florian,
> 
> On +2020-04-10 16:58:58 +0200, pelzflorian (Florian Pelz) wrote:
> > On Fri, Apr 10, 2020 at 04:38:37PM +0200, Ludovic Courtès wrote:
> > > AIUI, uvesafb is needed for ksmcon (or presumably X11) to work, but it’s
> > > not necessary to get the standard Linux framebuffer/console running
> > > (indeed, you were able to ctrl-alt-f3 to get a terminal).  Is this
> > > correct?
> > 
> > Yes, all correct.
> 
> Did you mean s/ksmcon/kmscon/ ? If that is a descendant of David Herrmann's 
> work,
> I wonder if it wouldn't just look for /sys/class/drm/card0 and, if found,
> ignore /dev/fb0 and the uvesafb (along with the latter's user stuff 
> requirements).
> 
> > 
> > 
> > > If that’s the case, then I think it’s acceptable for now to install a
> > > system that lacks uvesafb.  Of course X11 won’t work (right?),
> > 
> > Yes, right.
> >
> 
> Is that as absolutely right as it sounds?
> I had thought that some version of Wayland/weston had a back end that
> could run on plain /dev/fb0, and if so could provide Xwayland for X11 clients.
> 
> Of course, if /sys/class/drm/card0 is available, Wayland will prefer that,
> and you're home free for all kinds of GUIs.
>

Sorry, forgot to add this in context:

This "hello world" might suggest what you could do at a direct-to-wayland level,
without involving major GUI libs at run time:

    https://gitlab.com/hdante/hello_wayland

(it compiled and ran fine on my PureOS debian-based system, sharing display
with gnome as just another wayland client, since all the GUI runs on wayland)

I'm sure someone with more guile-fu than me could provide a guile wrapper
to vary text and cursor etc. faster than I can.
I've been meaning to do it, but time flies :)

It looks to me like a way to produce a fancy UI for a small runtime by using 
guix to
define build-time use of major graphics and font resources etc. for the run-time
wayland client.

> > > which is
> > > not great, but people can hopefully address it at the console until we
> > > have a better fix, possibly using ‘kernel-module-configuration-service’
> > > as you write.
> > > 
> > > WDYT?
> > 
> > I agree.
> > 
> > I will try making a patch including your suggestions in a few hours.
> > > 
> > 
> > >   2. Does "modprobe.d/uvesafb.conf" work?  I thought there was nothing
> > >      taking care of creating “modprobe.d” automatically.
> > 
> > I think I tested this version of the patch and it worked.  One can
> > test on QEMU by passing nomodeset (without uvesafb the installer stays
> > black, I think).  It also matches the description of
> > kernel-module-loader-service-type that was recently added to the
> > manual.
> > 
> > Regards,
> > Florian
> > 
> > 
> > 
> 
-- 
Regards,
Bengt Richter