Subject: Re: wsdisplay, early consoles etc.
To: Michael Lorenz <>
From: Bill Studenmund <>
List: tech-kern
Date: 11/05/2006 13:01:32
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Sun, Nov 05, 2006 at 01:36:07PM -0500, Michael Lorenz wrote:
> Hash: SHA1
> Hello,
> On Nov 5, 2006, at 12:32, Bill Studenmund wrote:
> >>I guess no protest means no objections?
> >
> >For some reason, I'm having a negative reaction to the use of=20
> >"overwrite".
> >And I'm not sure if it's really a problem or not.
> During autoconf it's not as far as I can tell.


> >I think I like the idea of being able to use a simple console driver=20
> >then
> >update to a more sophisiticated one once we know the hardware. And I=20
> >like
> >the idea about MI console description.
> My main motivation is the problem we'd have with selecting an early=20
> console driver before autoconf runs. We'd need some sort of=20
> mini-autoconf before autoconf so better have some simple catch-all and=20
> let autoconf select the one we'll end up using.

I think I do like the idea of avoiding a "mini-autoconf". So do what=20
you're suggesting.

> >So let me try this question. Why should the console be updated only=20
> >once?
> Good question - mainly because the current wsdisplay_cnattach() has a=20
> KASSERT() that makes sure it's only called exactly once and I'd assume=20
> whoever put it there had a good reason to do so.
> I'm not sure what would break if we'd allow moving the console around=20
> at runtime - probably not much.

I think the original idea was to make sure that we didn't mess code up and=
try to attach twice. It's one thing to attach something different, it's=20
another to try and attach the same thing (or what's supposed to be the=20
same thing) more than once.

I now really like the idea of having a routine for "Hey, make this the new=
console driver now". Among other things, we could load a console driver=20
after boot and have it take over. To go a bit more extreme, we could load=
a driver and have it take over, and then have the driver unload and fall=20
back to the old driver. :-) Probably would only be used by someone=20
developing a console driver, but it'd be cute.

Take care,


Content-Type: application/pgp-signature
Content-Disposition: inline

Version: GnuPG v1.4.3 (NetBSD)