Re: fbdev broken in current bk for PPC

On Fri, 10 Sep 2004, Antonino A. Daplas wrote:

On Friday 10 September 2004 10:23, Benjamin Herrenschmidt wrote:

quoted

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


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