On Sat, Feb 07, 2026 at 07:20:04PM +0100, Kirill A. Korinsky wrote:
> On Sat, 07 Feb 2026 14:11:05 +0100,
> Vitaliy Makkoveev <mvs@openbsd.org> wrote:
> > 
> > On Fri, Feb 06, 2026 at 06:39:03PM +0100, Kirill A. Korinsky wrote:
> > > > > 
> > > > > What about my suggestion to have a dummy framebuffer?
> > > > > 
> > > > 
> > > > I had tried, but I wasn't able make something that works.
> > > > 
> > > > Or better to say all my attemt leads to that machine still hungs.
> > > > 
> > > > Here hard part: this is remote machine, I haven't got access to serial
> > > > console on it, I can only boot it, or boot in "rescue mode" (Linux) or as
> > > > to attach KVM.
> > > > 
> > > > ... and without the way to debug I can't figure out why and where it hangs.
> > > >
> > > 
> > > Shall I drop this diff ?
> > > 
> > 
> > I agree with Mark. The dummy console which you intentionally enable via
> > /etc/boot.conf like "set tty dummy" is the right way.
> > 
> 
> Well, I think this is another feature.
> 
> On this machine, it doesn't matter whether I set tty dummy or com0.
> 
> However, Linux boots headless on this machine and uses vgaarb for the video
> card, even though nothing is connected to it. My diff replicates the logic
> to decide that it is safe to use as VGA compatible card.
> 
> I think we need https://marc.info/?l=openbsd-tech&m=176980480915521&w=2 to
> support this setup, as I've seen a few reports of similar behavior.
> 

This machine boots only if it has monitor connected, right? Otherwise it
panics somewhere. Seems your video card reports wrong data in the
headless mode. Linux handles it, but we don't. We do (*cn_probe) of all
available console devices, regardless on 'set tty' setting, so seems you
panic at (*cn_probe) stage. Fixing this is the right way.

> Do we need a dummy tty? Probably, but it's a different feature.
> 
> -- 
> wbr, Kirill
>