Fix Xorg modesetting on vc4 + skip enable_gpu on Pi 4+ (FullPageOS #708) - #276
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On Pi 5 with vc4-kms-v3d, Xorg autoconfig tries to use both the fbdev driver (on /dev/fb0) and the modesetting driver (on /dev/dri/card1), which causes: (EE) Cannot run in framebuffer mode. Please specify busIDs for all framebuffer devices Fatal server error: no screens found This results in the FullPageOS kiosk (chromium) never starting on Pi 5 — issue guysoft/FullPageOS#708. The fix adds an Xorg OutputClass config that forces the modesetting driver for the vc4 DRM device, preventing the fbdev/modesetting conflict. Confirmed working on Pi 5 with a physical HDMI display: - lightdm starts (active) - matchbox-window-manager starts - chromium kiosk starts (--kiosk --app=http://localhost/...) - FullPageDashboard loads (HTTP 200) - xrandr shows HDMI-1 connected 1920x1200 Fixes: guysoft/FullPageOS#708
guysoft
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Sep 2, 2026
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Summary
Fixes the two real-hardware boot bugs reported in FullPageOS 1.0.0-rc1 (guysoft/FullPageOS#708):
Black screen with flashing cursor (Pi 5, Trixie): Xorg autoconfig matches
modesettingbut falls back to fbdev and dies with(EE) Cannot run in framebuffer mode. Please specify busIDs for all framebuffer devices, so lightdm restart-loops forever and the display stays black. Ship/etc/X11/xorg.conf.d/99-vc4.conf(OutputClass: MatchDriver vc4 → modesetting, PrimaryGPU) so X binds the KMS device.Unwanted first-boot behavior from
enable_gpu(runs on every Pi): the scriptseds a wrong path (/opt/custompios/scripts/scripts/start_gui, doublescripts/), editscmdline.txt/config.txt, and callsshutdown -r nowunconditionally on first boot — the "reboots itself a couple times" reports. On Pi 4+/5 vc4 KMS is already the default, so the script now detects the model and skips (touching/etc/gpu_enabled).Hardware verification (rig: Pi 5, HDMI capture card)
99-vc4.conf+systemctl start lightdm: Chromium kiosk starts and the FullPageOS welcome page renders on HDMI (logo, QR, bit.ly/FPOSSETUP).Notes
enable_gpuskip uses the revision codemodel_id = hex & 0xffff>= 0x0040 check to detect Pi 4+ / newer models.Based on: guysoft/FullPageOS#708 (beakercs's confirmed workaround)