Re: Console handling (was: Re: Let's vote for PnP on 2.2)

G. Sumner Hayes (
Thu, 11 Dec 1997 01:05:53 -0500

On Wed, Dec 10, 1997 at 01:03:03PM +0000, H. Peter Anvin wrote:
> Followup to: <>
> By author: "Albert D. Cahalan" <>
> In newsgroup:
> >
> > > 1. Make the kernel know how to reset the video card to a known state.
> >
> > You can go from a known state to a known state.
> > You can go from any state to an unknown state -- useless.
> > Sorry, you can't get to a known state from an unknown state.
> >
> Sure you can. It's pretty common to do so. In fact, whenever you
> initialize hardware, this is usually exactly what you do.

The kernel can't do this in general, which is what Albert was trying
to say. The only way to initialize some video cards is a hard reset,
cutting the power. My old Cirrus was like this; if it was frobnicated
by SVGALib, neither Ctrl-Alt-Del nor hitting the reset button on my
machine would fix it. It took a full on/off of the power switch to set
it right.

These things have write-only registers whose current value affects
how other registers change when you write to them; some of them are
co-affected by other, similar registers. Cirrus aren't the only ones
like that, either. VGA hardware is really disgusting.


rage, rage against the dying of the light