kern/57451: drm doesn't attach an fb device if no monitor is connected

[chuq%chuq.com@localhost]

>Number:         57451
>Category:       kern
>Synopsis:       drm doesn't attach an fb device if no monitor is connected
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jun 04 01:35:00 +0000 2023
>Originator:     Chuck Silvers
>Release:        NetBSD 10.0_BETA or NetBSD 10.99.*
>Organization:
NetBSD
>Environment:
Architecture: x86_64
Machine: amd64
>Description:

If a system boots with no monitor connected, the current drm code
will not attach an fb device, for radeon, nouveau or intel.
This means that if the system has no serial port or other device
eligible to be the system console, the system will panic during boot
due to not finding a console device.  at least, I think it panics...
I can't really be sure what it does because there's no console.

If the system does have some other device to be the console, the
system survives the boot process but there are still problems.
/etc/rc.d/wsconscfg runs at boot time to apply various configuration
settings from /etc/wscons.conf, but if the driver did not attach
because of no monitor then some of those ws* commands will fail, and
then if you later plug in a monitor while the system is up, the
settings that were supposed to be applied at boot time are missing,
and you need to run /etc/rc.d/wscons manually to get the correct
configuration.

>How-To-Repeat:

Boot a system with the drmkms video drivers configured and
no monitor connected.

>Fix:

TBD