Loading display drivers in initrd (~3s) before RP1 PCIe southbridge
is ready (~12s) causes 'Cannot find any crtc or sizes' because the
DSI encoder isn't reachable. Rex loads these via udev late in boot.
- boot.initrd.kernelModules: only ocp8178_bl (backlight, RP1-independent)
- boot.kernelModules: vc4 + panel_cwu50 loaded in stage 2 after RP1
Rex's Trixie images use [pi5] for the CM5 display overlays
(clockworkpi-uconsole-cm5, vc4-kms-v3d-pi5). The nixos-uconsole
module generates [cm5] which the firmware may not apply on
some CM5 EEPROM configurations. Adding explicit [pi5] section
ensures the display overlays are always loaded.
The ter-v24n Terminus font renders garbled on CM5 DSI 720x1280
panel (green stretched line across screen). Switching to the
kernel's built-in Lat2-Terminus16 font for correct text rendering.
GPIO 23 service used gpioset 0 23=1 on BCM2712 chip 0 instead
of the RP1 chip (base 512), writing to a critical pin and
freezing the system. Commented out until correct chip is confirmed.
SSH opened with PasswordAuthentication + PermitRootLogin for
first deployment. Lock down after initial boot.
sysfs node is read-only (0444), even root cannot write.
The AXP228 PMU manages power path in hardware.
Practical fix: disconnect batteries during heavy builds.
The nixpkgs attribute for userspace GPIO tools is 'libgpiod',
not 'gpiod'. This provides the gpioset binary used by the
GPIO 23 internal USB hub service.
- Add disko flake input + partition config (/boot/firmware, /, /home)
- Add cm5-backlight-fix service as display fallback
- Add enable-gpio23-usb-hub service for internal USB hub
- Add mt7921u kernel module for MediaTek AC1200 WiFi
- Add gpiod package for GPIO userspace control
