NVRM 2.3.6: internal panel detected (EDID read), but NVRMBacklightHandler is never created - no brightness control #78

Environment

• macOS 15.8.1 (24H32), OpenCore, SMBIOS MacBookPro16,2
• CPU: AMD Ryzen 9 9955HX
• GPU: NVIDIA (PCI 10de:..., class 0x030000), driver com.nullmoth.NVRM / NVRMFB / NVAccel 2.3.6
• Boot-args include: nvfb=1 nvaccel=1 nvfbheads=4 -nvkmsnosmooth
• Internal panel: EDID is read correctly (IODisplayEDID present); EDID vendor 0x09e5 (BOE)
• Display works otherwise: resolution, refresh, acceleration all fine

Symptom

• No brightness slider in Control Center / System Settings
• Brightness keys do nothing
• ioreg -c AppleBacklightDisplay → 0 instances
• ioreg -c NVRMBacklightHandler → 0 instances
• ioreg -c NVRMNVDAFramebuffer shows the framebuffer up with IODisplayEDID and
  IODisplayConnectFlags = 0x00080000

Relevant strings in your binaries

NVRMFB.kext:

fb%u: backlight handler allocation failed
fb%u: backlight handler attach failed
fb%u: internal panel, but NVKMS registered no backlight (0x%x) -- no brightness control
fb%u: panel backlight at %u%% -- brightness keys and slider through AppleBacklightDisplay
NVRM-fb: backlight: brightness parameters on %s, panel at %d%%
NVRM-fb: backlight: setting %u%% failed (0x%x)

NVRM.kext:

backlight: display 0x%x brightness query status 0x%x, level %u
backlight: internal displays status 0x%x, mask 0x%x, available mask 0x%x
backlight: no internal display answered the brightness query, none registered

So the failure path looks like -- no brightness control (NVKMS reports no backlight for
this panel) rather than a driver bug on the macOS side.

What I have tried

• SSDT-PNLF is not applicable here (the ACPI backlight device
  \_SB.PCI0.GP17.VGA.LCD with _BCL/_BCM belongs to the AMD iGPU, and your driver
  goes through AppleBacklightDisplay itself), so I did not add it.
• No backlight-related boot-arg found in the 2.3.6 binaries.

Questions

1. Does 2.3.6 support backlight on a BOE panel that only exposes brightness through
   DPCD (eDP AUX) — or does it require a PWM / EC path?
2. Is there a boot-arg or Info.plist switch to force-register a backlight
   (NVRMBacklightHandler) for a panel NVKMS does not classify as backlight-capable?
3. If this needs a code change, would you accept a patch / a log run with debug output to
   see what backlight: internal displays status ... mask ... reports on this panel?

I can provide a full ioreg dump of NVRMNVDAFramebuffer, the EDID blob, and run any
debug build you want to try.