Re: FreeBSD/X11: Howto revive DisplayPort?

On Wed, 26 Nov 2025 22:31:20 +0100
Lars Tunkrans <[email protected]> wrote:

> HI
> 
>     Yes I  have  same experience.
> 
>     I beleive its because the  DDC/ EDID   info sent from screen over  
> the  connection cable
>     is  lost  if  the  KVM  and screen is not connected to the computer 
> at start up.
>      If I make sure that  the screen is attached to  the computer when 
> the computer powers up
>       a  Usable resoultion/timing is selected by the graphics card.
> 
>    Regards.

Exactly.
this behaviour is observed by myself on FreeBSD, Linux or Windows, on the contrary, seems
to have a solution to reestablish a DP connection, so it might be possible on FreeBSD
also (but is somehow by default disabled, I hope).

Having for computer attached to one KVM, three of them are FBSD boxes and one is a Linux
based commercial product provided by my employer leaves me with trouble when powering up
all machines.

Kind regards,

oh

> 
> 
> Den 2025-11-26 kl. 16:37, skrev FreeBSD User:
> > Using FreeBSD CURREN and FreeBSD STABLE/15.
> > Also, most systems are attached to a KVM switch, connected via DP.
> >
> > Hosts booting all UEFI.
> >
> > On hosts using X11/xdm GUI, switching forth and back to the output/host I want to use
> > DP does obviously not "lose" DP output, so after graphics has been initialized I'm
> > able to see the GUI.
> >
> > The situation is completely different with plain consoles, provided by FreeBSD's
> > EFI/UEFI simple framebuffer device driver. Working on the console on one host,
> > switching to another host, working there and trying to switch back leaves me with no
> > output anymore! I see this behaviour with different types of KVM switches I have at
> > hand.
> >
> > Can this behaviour be changed, even with no X11?
> >
> > Thanks in advance and wishes,
> >
> > O. Hartmann
> >