Re: [Linux-fbdev-devel] fbdev broken in current bk for PPC

Geert Uytterhoeven
2004-09-11T07:20:37Z

On Fri, 10 Sep 2004, Antonino A. Daplas wrote:
> On Friday 10 September 2004 10:23, Benjamin Herrenschmidt wrote:
> > Recent changes upstream are breaking fbdev on pmacs.
> >
> > I haven't had time to go deep into that (but I suspect Linus sees it
> > too on his own g5 unless he removed offb from his .config).
> >
> > From what I see, it seems that offb is kicking in by default, reserves
> > the mmio regions, and then whatever chip driver loads can't access them.
> >
> > offb is supposed to be a "fallback" driver in case no fbdev is taking
> > over, it should also be "forced" in with video=ofonly kernel command
> > line. This logic has been broken.
>
> Actually, I was thinking about this problem with offb. I was planning on
> adding video=offb:off support for offb, and then place offb at the very top
> drivers Makefile (the reason why I placed it there, but forgot to add the
> setup support for offb). So, without the 'off' option, offb becomes the
> first driver that gets initialized by reason that it's at the top, and with
> the 'off' option, it just exits initialization immediately, giving the other
> drivers a chance to get through.

This is not suitable, since for dual-headed machines, you may want to have one
card driven by its native driver, and the other by offb (as fallback, because
no driver exists yet).

> The second method is not harder but will involve, again, changes to all
> drivers. The only sane method I can think of is to change fb_get_options so
> it returns an error if:
>
> a. "off" option is enabled
> b. "ofonly" is enabled but only if name != "offb"
>
> If fb_get_options returns an error, drivers will not proceed with their
> initialization. The second method is more compatible with the
> previous setup semantics.

Yes, looks better (except that it's less clean, but I'm afraid we can't fix
that easily).

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds