maintainer-feedback requested: [Bug 289244] X11/xorg: auto detection doesn't work on muxed (igpu+dgpu)

Bugzilla Automation <bugzilla@FreeBSD.org> has asked freebsd-x11 (Nobody)
<x11@FreeBSD.org> for maintainer-feedback:
Bug 289244: X11/xorg: auto detection doesn't work on muxed (igpu+dgpu)
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=289244



--- Description ---
Hi,

I have a System76 Serval WS 13 as my desktop. it has a muxed intel igpu + RTX
4060 dgpu. Apparently, the main display is attached only to the iGPU (despite
being muxed), however it can be offload/sink to nvidia dGPU.

Providers: number : 2
Provider 0: id: 0x1b7 cap: 0x0 crtcs: 4 outputs: 6 associated providers: 0
name:NVIDIA-0
Provider 1: id: 0x1fd cap: 0xf, Source Output, Sink Output, Source Offload,
Sink Offload crtcs: 4 outputs: 5 associated providers: 0 name:modesetting

I'm using 15-CURRENT (1d1265875593) and both of my nvidia-drm and i915kms
drivers are loaded and working perfectly.

The problem is i have to configure xorg.conf manually to detect my main monitor
and external monitors together.

When I was less experienced with xorg, I had to define the "Monitor" and
"Screen" sections of my main display to use the intel "Device". After some time
I figured out that I could define my xorg.conf like this:

Section "OutputClass"
    Identifier "intel"
    MatchDriver "i915kms"
    Driver "modesetting"
EndSection

Section "OutputClass"
    Identifier "nvidia"
    MatchDriver "nvidia-drm"
    Driver "nvidia"
    Option "AllowEmptyInitialConfiguration"
    Option "PrimaryGPU" "yes"
EndSection

After upgrading from just before 15-PRELEASE to 1d1265875593, I have to define
my "BusID" in the "Device" section again:

Section "Device"
  Identifier "nvidia"
  Driver "nvidia"
  VendorName "NVIDIA Corporation"
  BoardName "NVIDIA GeForce RTX 4060 Laptop GPU"
  BusID "PCI:1:0:0"
  Option "PrimaryGPU" "yes"
EndSection

Section "Device"
  Identifier "intel"
    Driver "modesetting"
    VendorName "Intel Corporation"
  BusID  "PCI:0:2:0"
EndSection

unfortunately, this isn't enough to detect both of my main display and other
external monitors.

N.B: i'm not sure whether this bug should be reported in base system or ports.
I think it belongs to the base system because the only thing I changed was
updating my userland (world) from a version before 15-PRERELEASE (15-CURRENT)
to now (1d1265875593)