Comment # 19 on bug 1179387 from Felix Miata (offline until ???)

(In reply to Stefan Dirsch from comment #16)
> Ok. Apparently with your gfx card, you have no framebuffer device at all. No
> idea why. Maybe it's time to get rid of this gfx card. Seriously.

Sorry to have mentioned Matrox. This bug is about old Radeons unsupported by
modeset(0).

> [   164.682] (EE) Unable to find a valid framebuffer device
> [...]
> [   164.683] (DB) xf86MergeOutputClassOptions unsupported bus type 0
> [...]
> [   164.698] (EE) FBDEV(0): FBIOPUT_VSCREENINFO succeeded but modified mode
> [   164.698] (EE) FBDEV(0): mode initialization failed

That's all about the very same rv250 Radeon 9000 AGP running instead on an
ancient 64 bit machine (the one I borrowed it from for testing 32bit), without
employing radeon.agpmode=-1. With it, all trouble ceases, contrary to 15.2's
5.3 kernel, where all works as expected without it:

# inxi -CGISay
System:
  Host: k8mmv Kernel: 5.3.18-lp152.57-default x86_64 bits: 64
  parameters:...mitigations=auto consoleblank=0
  Desktop: Trinity R14.0.9 tk: Qt 3.5.0 info: kicker wm: Twin 3.0 dm: TDM
  Distro: openSUSE Leap 15.2
CPU:
  Info: Single Core model: AMD Sempron 3000+ socket: 754 (940) note: check...
Graphics:
  Device-1: AMD RV250/M9 GL [Mobility FireGL 9000/Radeon 9000] driver: radeon
  v: kernel bus ID: 01:00.0 chip ID: 1002:4c66
  Display: server: X.Org 1.20.3 driver: ati,radeon
  unloaded: fbdev,modesetting,vesa display ID: :0 screens: 1
  Screen-1: 0 s-res: 3600x1200 s-dpi: 108 s-size: 846x282mm (33.3x11.1")
  s-diag: 892mm (35.1")
  Monitor-1: VGA-0 res: 1680x1050 hz: 60 dpi: 90 size: 474x296mm (18.7x11.7")
  diag: 559mm (22")
  Monitor-2: DVI-0 res: 1920x1200 hz: 60 dpi: 94 size: 519x324mm (20.4x12.8")
  diag: 612mm (24.1")
  OpenGL: renderer: Mesa DRI R200 (RV250 4C66) DRI2 v: 1.3 Mesa 19.3.4
  direct render: Yes
Info:...Shell: Bash v: 4.4.23 running in: konsole inxi: 3.1.09

On same PC, Debian 11 Buster's 5.9.x works as expected without need of
radeon.agpmode=-1, vga= or video= to produce 1920x1200 on DVI using Radeon and
FBDEV DDXes (along with (EE) FBDEV(0): FBIOPUTCMAP: Device or resource busy).