Raspberry Pi 4B secondary monitor not working

[carlosneves0]

Issue description

xserver + dmesg + udev -> no one logs anything as I plug/unplug the secondary HDMI cable; but the secondary monitor shows some gradient image.

Technical details

• system: "aarch64-linux"
• host os: Linux 5.10.17, NixOS, 21.11pre292520.540dccb2aea (Porcupine)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.3.11
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos

[nagy]

Maybe this can help you #63720 (comment)

[carlosneves0]

Thanks for the tip! After searching, I came up with this configuration:

boot.loader = {
    grub.enable = false;
    generic-extlinux-compatible.enable = true;
    raspberryPi = {
      enable = true;
      uboot.enable = true;
      version = 4;
      firmwareConfig = ''
        max_framebuffers=2
      '';
    };
  };

# nixos-rebuild switch && reboot

It did not work.

---

This worked:

# mount /dev/disk/by-label/FIRMWARE /mnt
# printf '\nmax_framebuffers=2' >> /mnt/config.txt
# umount /mnt && reboot

Is there a way to make the declarative config work?

[stale]

I marked this as stale due to inactivity. → More info

[patka-123]

Hello @carlosneves0 👋

It seems to me like your issue is solved. If so, would you be able to close this issue?

(I'm going through issues marked as stale to see what can be resolved. If this issue still exists then don't mind me)

[carlosneves0]

I can't validate whether it has been solved for good as I went with alpine for the raspberry-pi.

If I come back to try nixos again I'll check, and if I find any issues I'll come back here.

Let's close this issue.