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SubjectRe: Running JOBS list.
On Fri, 10 Mar 2000, James Simmons wrote:
> > Fbcon races
>
> I didn't finish the fbdev API changes. Its better but not perfect. You
> will see. I sent a patch to Geert to look over before he sends it to
> linus that updates vfb.c to show how a 2.4.X driver should be written. As
> for races. Its still not really multihead friendly. Neither is the console
> code as several of us with multihead system discover. SMP and multihead
> and console system don't mix :( The con2fb mapping is just a mess. Things
> like fbcon=map:0110 bombs if you don't have a second video card. Their is
> no way to fix this. Its a chicken and egg problem. fbcon_setup is called
> before fbmem_init so you can't do any sanity checking. The con2fb mapping
> stuff is just pure crap. Its just a pure hack to get multihead somewhat
> working. I hate it and can't wait to see it removed in 2.5.X.

But we can validate the contents of con2fb_map[] everytime it is used, right?

> The second problem is vgacon and fbcon. Until this last kernel you can
> boot vgacon and then inmod a fbdev driver and then fbcon would take over.
> Now the problem is most video card when they go from VGA mode to a non VGA
> mode can NOT go back to VGA mode. So if you go to rmmod the fbdev driver

So we cannot go back, but we can go forward.

And why can we rmmod the fbdev? It's supposed to be marked busy when fbcon is
using it.

> you are fubar. I just made a patch that changes the config.in files to
> have it so you either have to choose fbcon or vgacon. Its one or the

Yuk. This is very bad.

BTW, can't we just call take_over_console() again in register_framebuffer() so
we at least can do `insmod xxxfb' again?

> other. This brings me to another question. Can prom console run at the
> same time as the framebuffers on a sparc station ? Same for some of the
> SGI stations. Can a newport console also run at the same time as a
> framebuffer console. This way my patch can ensure you can select between
> fbcon or some other console type.

Promcon runs before fbcon, AFAIK.
SGI Indy boxes don't use fbcon, but solely newportcon.

> > Some FB drivers check the A000 area and find it busy then bomb out
>
> I know cirrus, dnfb, and vga16. I can see vga16 since this is really

Don't worry about dnfb (I assume your grep found `0x0FA0000'? :-). Dnfb is for
frame buffers in Apollo Domain boxes. No conflict with vgacon.

> for a isa card. vga16 should be called last since many cards start in VGA
> mode program a few registers then switch to MMIO thus freeing this region.
> Its then safe for the next card to do this. As for cirrus and dnfb. I
> don't have the docs for these cards but I assume it should be possible to
> switch to MMIO mode for these cards.

This is another problem: because in many cases the vgacon and the fbcon card
are the same device, there should be a possibility to ask vgacon to `release'
the card (and its resources) first. Replace `vgacon' with `offb' on
PowerMac/CHRP.

BTW, `insmod vga16fb' works fine on boxes without vgacon, where vga16fb does
the second video card :-)

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- Linux/{m68k~Amiga,PPC~CHRP} -- 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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