AMDGPU on TrueOS 12 Failed to open DRM device for pci:0000:01:00.0: No such file or directory

[Peter Peterson]

Hello, I've been trying to run a BSD on this r9 285 (Tonga) for quite a
while now and I saw that TrueOS (or PC-BSD) should have implemented the drm
linux4.6 driver. So I installed TrueOS on my machine and I can't get it to
work. It seems that it can't find something related to the DRM driver,
either that or it doesn't see anything at the pci bridge. I wonder if it's
firmware that it's trying to find, or if it's not seeing the card because
of a lack of firmware. I know the linux kernel requires some proprietary
firmware to get it working, I don't know if that firmware is also part of
the drm driver or comes with TrueOS's kernel. The vesa drivers work, but
the resolution isn't good and I'm on 2 monitors.

I pasted Xorg's logs here: https://paste.teknik.io/Simple/02gJt
and xorg config (I had it generated) here:
https://paste.teknik.io/Simple/nDXpm

I'm not sure if the FreeBSD mailing lists are the best place to ask about
TrueOS but I really would appreciate your help here. Thank you very much!