DRM: radeonkms no longer usable (and can not be unloaded (kernel panic)) following a switch to stable, FreeBSD 12.0-BETA1 r339438

[Graham Perrin]

$ uname -v
FreeBSD 12.0-BETA1 r339438 GENERIC
$ which xauth
/usr/local/bin/xauth
$

Radeon HD 7570M, HP EliteBook 8570p.

Following the switch to STABLE I could no longer use a desktop environment. For example:

service sddm onestart

– results in endless repetition of two lines, comparable to those shown at <https://forum.voidlinux.org/t/solved-sddm-crashes/4471> and <http://www.pclinuxos.com/forum/index.php/topic,141031.msg1204729.html#msg1204729> except FreeBSD has the different path to xauth so IIRC what's seen is:

…
/usr/local/bin/xauth: (stdin):1:  bad "remove" command line
/usr/local/bin/xauth: (stdin):2:  bad "add" command line
/usr/local/bin/xauth: (stdin):1:  bad "remove" command line
/usr/local/bin/xauth: (stdin):2:  bad "add" command line
…

kldunload radeonkms

– results in a kernel panic.

So I edited my rc.conf,

$ less /etc/rc.conf
# kld_list="/boot/modules/radeonkms.ko"
# sddm_enable="YES"
…

– changed the startup routine to include CSM (not UEFI alone) and created a driver-vesa.conf as shown at <https://forums.freebsd.org/threads/startx-no-screen-failure.65210/#post-382315>.

Now I can at least use VESA.