NixOS on Raspberry Pi 4 Model B | bluetoothctl issue: No default controller available

[yshym]

Issue description

"No default controller available" issue while trying to use bluetoothctl tool. I've recently installed NixOS on a Raspberry Pi 4 Model B using this very cool tutorial and everything seems to be fine for now except for this bluetooth functionality. I've read that https://github.com/RPi-Distro/pi-bluetooth is used in most similar cases, but, as far as I understand, btattach systemd service (https://nixos.wiki/wiki/NixOS_on_ARM/Raspberry_Pi_3#Bluetooth) is already doing the same (if it is suitable for both rpi 3 and 4)

rpi-related imports:

imports = [
  "${fetchTarball "https://github.com/NixOS/nixos-hardware/archive/936e4649098d6a5e0762058cb7687be1b2d90550.tar.gz" }/raspberry-pi/4"
];

systemd services:

systemd.services = {
  btattach = {
    before = [ "bluetooth.service" ];
    after = [ "dev-ttyAMA0.device" ];
    wantedBy = [ "multi-user.target" ];
    serviceConfig = {
      ExecStart = "${pkgs.bluez}/bin/btattach -B /dev/ttyAMA0 -P bcm -S 3000000";
    };
  };
};

hardware:

hardware = {
  # Enable GPU acceleration
  raspberry-pi."4".fkms-3d.enable = true;
  enableRedistributableFirmware = true;
  pulseaudio = {
    enable = true;
    support32Bit = true;
    extraModules = [ pkgs.pulseaudio-modules-bt ];
    package = pkgs.pulseaudioFull;
    extraConfig = ''
      load-module module-switch-on-connect
    '';
  };
  bluetooth.enable = true;
};

rfkill list all
0: hci0: Bluetooth
	Soft blocked: no
	Hard blocked: no
1: phy0: Wireless LAN
	Soft blocked: no
	Hard blocked: no

Steps to reproduce

bluetoothctl
Agent registered
[bluetooth]# power on
No default controller available

Technical details

• system: "aarch64-linux"
• host os: Linux 5.10.17, NixOS, 21.05pre-git (Okapi)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.3.11
• channels(yevhenshymotiuk): ""
• channels(root): "home-manager, nixos"
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos

[domenkozar]

Looking at google results it seems that some kernels broke Bluetooth support, so updating kernel to the latest revision in style of https://github.com/NixOS/nixpkgs/pull/118548 might fix it.

[yshym]

fkms-3d overlay can't be built with boot.kernelPackages = pkgs.linuxPackages_latest;:

Applying overlay rpi4-vc4-fkms-v3d-overlay to bcm2711-rpi-4-b.dtb

Failed to apply '/nix/store/igz72xqn4w32hgbgiz8ab4493kj87j63-rpi4-vc4-fkms-v3d-overlay-dtbo': FDT_ERR_NOTFOUND
builder for '/nix/store/5ma90bwh3j5ljg5p078yf8x5h19m7ixn-device-tree-overlays.drv' failed with exit code 1
cannot build derivation '/nix/store/amm3mv4c7hy203gbx9w1y3i044phry7w-nixos-system-rpi4-21.05pre-git.drv': 1 dependencies couldn't be built

[domenkozar]

Sorry, I meant packaging the latest raspberrypi kernel revision.

[yshym]

Oh, ok. I'll try it

[yshym]

A bit newer release doesn't fix the problem. Latest revisions from both rpi-5.11.y and rpi-5.12.y have compilation issues

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/raspberry-pi-4-bluetooth-audio/13876/2

[colonelpanic8]

A bit newer release doesn't fix the problem. Latest revisions from both rpi-5.11.y and rpi-5.12.y have compilation issues

What are the compilation issues? Are they not fixable?

[VergeDX]

Same issues here, I tried https://github.com/raspberrypi/linux/releases/tag/1.20211007 version.

[bbqsrc]

This remains to be an issue. Have hit this today using the pkgs.linuxPackages_rpi4 kernel.

[pschyska]

I noticed that console=ttyAMA0,115200n8 in my kernel commandline (via sd-image.nix) breaks bluetooth. I had a number of dmesg lines about hc0, e.g. hci0 command 0x0c03 tx timeout. Removing the ttyAMA0 entry made bluetooth work with something like

{
  imports = [  (modulesPath + "/installer/sd-card/sd-image-aarch64.nix") ];
  hardware = {
    bluetooth = {
      package = pkgs.bluez;
      enable = true;
      powerOnBoot = false;
    };
  };
}

nixpkgs@ 35db2e60df598e3d5c88adab65f70b91f6645b45, linuxPackages_latest.kernel.version = 5.16.12

I edited the kernel command line in extlinux.conf by hand for now, nixified it would probably look like this:

{
  # via sd-image: boot.kernelParams = ["console=ttyS0,115200n8" "console=ttyAMA0,115200n8" "console=tty0"];
  boot.kernelParams = lib.mkForce ["console=ttyS0,115200n8" "console=tty0"];
}

[Majiir]

@pschyska Could you share a full config with working bluetooth? And just in case, could you also share your /boot/config.txt? I have been unable to get bluetooth working by downgrading kernels or adopting any of the configs in this thread. If I manually run sudo btattach -B /dev/ttyAMA0 -P bcm -S 3000000, I can see the adapter with rfkill:

ID TYPE      DEVICE      SOFT      HARD                                                                                                                        │
 1 bluetooth hci0   unblocked unblocked 

but bluetoothctl power on still fails with No default controller available. I do see these errors in dmesg upon running btattach:

[  525.931400] Bluetooth: hci0: command 0x0c03 tx timeout                                                                                                      │
[  533.995470] Bluetooth: hci0: BCM: Reset failed (-110) 

but I do not have the problematic kernel command line params you referenced.

[pschyska]

@Majiir I'm afraid I can't. I switched to https://github.com/pftf/RPi4 and install nixos like on any other uefi system. I couldn't make the bluetooth controller appear in bluetoothctl any longer (the resulting installation is probably all kinds of broken now in other ways, but I have no clue about rpis). As I didn't end up using bluetooth I didn't notice. With the snippet above I did get it to work and was able to pair a device and didn't see any issues. I also can't experiment much because I need my rpi working for some network functions. Sorry

[pschyska]

@Majiir I recently worked on my system again, and was able to use bluetooth with upstream kernels 5.15.63 (linuxPackages @ nixos-unstable) and 5.19.4 (linuxPackages_latest). I didn't do anything special. I'm not importing nixos-hardware.

config.txt:

arm_64bit=1
enable_uart=1
uart_2ndstage=1
enable_gic=1
armstub=RPI_EFI.fd
disable_commandline_tags=1
disable_overscan=1
device_tree_address=0x1f0000
device_tree_end=0x200000
dtoverlay=miniuart-bt
#dtoverlay=upstream-pi4

(upstream-pi4 always crashed the system during boot) EEPROM is https://github.com/raspberrypi/rpi-eeprom/blob/master/firmware/stable/pieeprom-2022-08-02.bin RPI_EFI and the boot code is from https://github.com/pftf/RPi4/releases/tag/v1.33. I have a 4 B rev 1.1 with 4G RAM and removed the 3G limit in UEFI and set the boot mode to ACPI+DeviceTree (with just ACPI I'm missing a lot of functionality like raspberrypi_cpufreq).

relevant nix config:

{pkgs, ...}: {
  boot = {
    loader = {
      timeout = 3;

      # requires uefi firmware!
      systemd-boot = {
        enable = true;
        consoleMode = "max";
      };
      efi.canTouchEfiVariables = true;
      generic-extlinux-compatible.enable = false;
    };
    kernelPackages = pkgs.linuxPackages_latest; # or without _latest
    # kernelParams not set, defaults to = ["loglevel=4"];

    initrd.availableKernelModules = [ "pcie-brcmstb" "reset-raspberrypi" ]; # USB hid in initrd to unlock luks devices
  };

  hardware.enableRedistributableFirmware = true;
  hardware.deviceTree.filter = "bcm2711-rpi-4-b.dtb";
  systemd.services."getty@".enable = false;
  powerManagement.cpuFreqGovernor = "schedutil";
}

Bear in mind that depending on you UART settings, the bluetooth device is either /dev/ttyAMA0, or one of the /dev/ttyS* (IIRC it was /dev/ttyS1 for me with miniuart-bt, but for most it's /dev/ttyS0, IDK why it moved to the 1 for me ¯\(ツ)/¯). In either case, make sure you don't put a linux console onto this device (e.g. with the referenced kernel params, or via enabling getty@tty* or similar). If you use mini UART, you have to update btattach -B /dev/ttyS0 -P bcm -S 3000000 accordingly. Afterwards I systemctl restart bluetooth and could the the controller in bluetoothctl, and could power on and scan on and got results.

I can't give you the full config, is split up into many modules within my system flake, but I can query specific config values in repl for you if you want to know more.

[Majiir]

Thanks, @pschyska. I tried pieces of your config, and I narrowed the issue down to, believe it or not, the kernel: linuxPackages works fine, but linuxPackages_rpi does not.

(Also, I'm using sd-image-aarch64.nix as a base, so I had to set kernelParams = lib.mkForce [ "console=ttyS0,115200n8" "console=tty0" ] in order to remove the default console=ttyAMA0,115200n8 parameter.)

I don't think the issue is in the kernel itself, since I had bluetooth working when running the same kernel version on Raspberry Pi OS. I'll run some more experiments to verify one way or the other.

[pschyska]

Thanks, @pschyska. I tried pieces of your config, and I narrowed the issue down to, believe it or not, the kernel: linuxPackages works fine, but linuxPackages_rpi does not.

I assume you mean linuxPackages_rpi4 and it's not hard to believe that this is the issue 🙁 Raspberry foundation are doing some things that upstream kernel doesn't agree with, IIUC, beginning with the naming of the SoC in DeviceTree (e.g. for pi3-b, rpi foundation calls it bcm2710-rpi-3-b. and upstream kernel bcm2837-rpi-3-b, although it looked like at least for the 4's both name it bcm2711, but I'm no expert...) and probably custom kernel modules, firmware blobs and so on. Did you take a look at nixos-hardware/raspberry-pi/4 and its includes? This config is supposed to work with linuxPackages_rpi4. In particular, you need hardware.enableRedistributableFirmware so that you get pkgs.raspberrypiWirelessFirmware.

[ChanceHarrison]

Is btattach a requirement to get the Pi 4B's Bluetooth working (once everything is configured properly)? If so, would it make sense to "fix" this in nixos-hardawre with some combination of udev rules and systemd services to start btattach automatically?

[Majiir]

There's also the krnbt device tree parameter:

        krnbt                   Set to "on" to enable autoprobing of Bluetooth
                                driver without need of hciattach/btattach
                                (default "off")

I read that krnbt is the preferred approach, but I can't recall where I read that. It's certainly simpler, when it works.

Thing is, I haven't been able to get btattach to work either. To summarize, these are the results I'm seeing:

• NixOS with default kernel: works
• NixOS with Raspberry Pi kernel: broken!
• Raspberry Pi OS with Raspberry Pi kernel: works

[ChanceHarrison]

@Majiir Thanks for the mention of krnbt; I didn't know it existed.

I have btattach and NixOS with the Raspberry Pi kernel working. Funny enough, I can't boot with the default kernel.

Here is what works for me.

configuration.nix

boot.kernelParams = [
  "8250.nr_uarts=1"
  "console=ttyS0,115200"
  "console=tty1"
];
boot.kernelPackages = pkgs.linuxPackages_rpi4;

hardware.bluetooth.enable = true;

(I think those are the only relevant lines)

config.txt

[pi4]
kernel=Tow-Boot.noenv.rpi4.bin
enable_gic=1
armstub=armstub8-gic.bin
disable_overscan=1

[all]
arm_64bit=1
enable_uart=1
avoid_warnings=1

nix-info -m

• system: "aarch64-linux"
• host os: Linux 5.15.32, NixOS, 22.11 (Raccoon), 22.11pre418904.db25c4da285
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.11.0
• channels(root): "nixos"
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos

Perhaps that can help you narrow down what isn't working for you? Happy to provide any extra information.

[Majiir]

@ChanceHarrison Could you share the btattach command you are using?

[ChanceHarrison]

Of course! I knew I was forgetting something.

btattach -B /dev/ttyAMA0 -P bcm

[ChanceHarrison]

There's also the krnbt device tree parameter: - @Majiir

Edit: It works just fine for me, if you type it correctly. 😉

Original text: For what it's worth, adding dtparm=krnbt=on to my config.txt and rebooting didn't change anything; I still had to use btattach to get bluetoothctl to see the controller. Am I doing something obviously wrong? Do I also have to set the krnbt_baudrate param? I'm not well-versed in debugging device tree shenanigans.

[Majiir]

I'm not well-versed in it either, but I only needed the dtparam=krnbt=on line. That worked for me in NixOS (with the default kernel) and also in Raspberry Pi OS (with the btattach systemd units disabled).

Your post says dtparm, but it should be dtparam - did the same typo make it into your config?

[ChanceHarrison]

Your post says dtparm, but it should be dtparam - did the same typo make it into your config?

D'oh! The typo made its way into the config first, actually. Thank you for catching it. It works as advertised if you actually type it correctly.

I think there are some lessons learned here that can be documented on the wiki, perhaps? I would be happy to try my hand at those changes, though I have never done so before.

As for your issue, did you have any luck finding why Bluetooth (either via btattach or krnbt) is working for me and not for you?

[Majiir]

No such luck! I tried using the same nixpkgs commit, the same NixOS config, and the same config.txt contents. The behavior is the same every time: btattach runs, and rfkill shows a device:

$ rfkill
ID TYPE      DEVICE      SOFT      HARD
 0 bluetooth hci0   unblocked unblocked

but still no working Bluetooth:

$ bluetoothctl power on
No default controller available

dmesg reports:

[  204.090325] uart-pl011 fe201000.serial: no DMA platform data
[  204.116448] Bluetooth: HCI UART driver ver 2.3
[  204.120994] Bluetooth: HCI UART protocol H4 registered
[  204.126231] Bluetooth: HCI UART protocol BCSP registered
[  204.131728] Bluetooth: HCI UART protocol LL registered
[  204.137010] Bluetooth: HCI UART protocol Three-wire (H5) registered
[  204.143629] Bluetooth: HCI UART protocol Broadcom registered
[  204.149465] Bluetooth: HCI UART protocol QCA registered
[  204.317159] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[  204.322579] Bluetooth: BNEP filters: protocol multicast
[  204.328044] Bluetooth: BNEP socket layer initialized
[  206.174626] Bluetooth: hci0: command 0x0c03 tx timeout
[  214.238705] Bluetooth: hci0: BCM: Reset failed (-110)

In all of my testing, the only thing that works is switching to the default kernel instead of linuxPackages_rpi4. But the issue isn't the Raspberry Pi kernel itself, because that kernel works with both manual attachment and krnbt on other distros.

I put together a minimal-ish system flake for testing this: https://github.com/Majiir/btpi You can build an SD image with nix build --flake '.#btpi-sd, or you can rebuild an existing system with nixos-rebuild --flake '.#btpi'.

@ChanceHarrison Would you be willing to build a fresh SD image and give that a try? If it works, then that narrows the issue down to hardware or firmware. If it doesn't, then maybe you can make adjustments or offer an alternative flake that does work.

[EDIT] Just to rule out this one device being the problem, I tested the btattach method on a Raspberry Pi Compute Module 4 with a similar config, and I'm seeing the same issue.

[ChanceHarrison]

Would you be willing to build a fresh SD image and give that a try? - @Majiir

I would be willing to give it a try, yes. I'll get back to you in a few days once I have a new spare SD card to use. To make sure I'm clear on the process:

1. Grab https://hydra.nixos.org/job/nixos/trunk-combined/nixos.sd_image.aarch64-linux, dd onto SD, and boot
2. git clone https://github.com/Majiir/btpi and cd btpi
3. nixos-rebuild --flake '.#btpi'

Or, would I just do step 2 (on an existing NixOS system) and nix-build --flake '.#btpi-sd' and then dd output (where does the output go?) onto SD and boot? Excuse my lack of understanding there, but does /etc/nixos/configuration.nix get populated when building an SD image this way?

Of note, I am not using the SD image to get NixOS on my Pi. I used the aarch64 minimal installer (specific version nixos-minimal-22.11pre409157.da6a05816e7-aarch64-linux.iso, though I don't know how to find the build on Hydra) that I wrote to a USB flash drive. I wrote Tow-Boot (the shared.disk-image.img from raspberryPi-aarch64-2021.10-005) on the SD card for UEFI booting. From there, I installed NixOS onto a SSD (also connected via USB). Do you think it's possible that the differences in our observed behavior are because I'm not using the SD image and you are? I suppose we might find out when I give the SD image route a try myself.

[Majiir]

We have a few different options. For best reproducing my setup, you should do something like this:

git clone https://github.com/Majiir/btpi
cd btpi
nix build '.#btpi-sd'
ls result/sd-image

Then, you can write that image to an SD card, boot the Pi, and log in with test/test.

The SD image will create a config.txt that contains dtparam=krnbt=on, but that can be manually removed by mounting the firmware partition (mount /dev/disk/by-label/FIRMWARE) and editing /boot/firmware/config.txt. It shouldn't make a difference to the test (except that, y'know, Bluetooth might just work when you boot up).

If you do all that, you won't have anything in /etc/nixos. You can clone the repo to the Pi and nixos-rebuild switch --flake '.#btpi' there, or you can remotely deploy from another machine with --target-host.

My thinking is that by using a flake and building the whole SD image, we ideally get the exact same setup, and Bluetooth should fail for you with that setup. If it does, you could try taking your existing, working system (after taking a backup!) and deploy the minimal flake with nixos-rebuild. The results will be interesting! Thank you for taking the time to test this out.

Meanwhile, I will see if I can replicate your install steps.

[ChanceHarrison]

@Majiir I finally got my spare SD card(s) and I went ahead and booted my Pi with your minimal example. Thanks for the guidance on using it. Sure enough, I run into the same Bluetooth issues. Adding hardware.enableRedistributableFirmware = true; and rebuilding the system with the flake didn't help.

I compared dmesg output between my known-good system and the minimal example system. Here's the two outputs:

Known good:

[   11.921327] Bluetooth: HCI device and connection manager initialized
[   11.921345] Bluetooth: HCI socket layer initialized
[   11.921364] Bluetooth: L2CAP socket layer initialized
[   11.921383] Bluetooth: SCO socket layer initialized
[   12.073632] Bluetooth: HCI UART driver ver 2.3
[   12.073653] Bluetooth: HCI UART protocol H4 registered
[   12.073658] Bluetooth: HCI UART protocol BCSP registered
[   12.073741] Bluetooth: HCI UART protocol LL registered
[   12.076474] Bluetooth: HCI UART protocol Three-wire (H5) registered
[   12.079804] Bluetooth: HCI UART protocol Broadcom registered
[   12.441954] Bluetooth: hci0: BCM: chip id 107
[   12.442231] Bluetooth: hci0: BCM: features 0x2f
[   12.443316] Bluetooth: hci0: BCM4345C0
[   12.443335] Bluetooth: hci0: BCM4345C0 (003.001.025) build 0000
[   12.456244] Bluetooth: hci0: BCM4345C0 'brcm/BCM4345C0.hcd' Patch
[   13.144837] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[   13.144857] Bluetooth: BNEP filters: protocol multicast
[   13.144877] Bluetooth: BNEP socket layer initialized
[   13.167354] Bluetooth: hci0: BCM43455 37.4MHz Raspberry Pi 3+
[   13.167377] Bluetooth: hci0: BCM4345C0 (003.001.025) build 0342

btpi (with enableRedistributableFirmware):

[    9.122898] Bluetooth: Core ver 2.22
[    9.140820] Bluetooth: HCI device and connection manager initialized
[    9.141508] Bluetooth: HCI socket layer initialized
[    9.141536] Bluetooth: L2CAP socket layer initialized
[    9.141972] Bluetooth: SCO socket layer initialized
# btattach
[  437.675481] uart-pl011 fe201000.serial: no DMA platform data
[  437.705865] Bluetooth: HCI UART driver ver 2.3
[  437.710439] Bluetooth: HCI UART protocol H4 registered
[  437.715687] Bluetooth: HCI UART protocol BCSP registered
[  437.721161] Bluetooth: HCI UART protocol LL registered
[  437.726454] Bluetooth: HCI UART protocol Three-wire (H5) registered
[  437.733011] Bluetooth: HCI UART protocol Broadcom registered
[  437.738863] Bluetooth: HCI UART protocol QCA registered
[  439.777322] Bluetooth: hci0: command 0x0c03 tx timeout
[  447.969540] Bluetooth: hci0: BCM: Reset failed (-110)

I also confirmed that switching to the non-rpi4 kernel (I tried with linuxPackages_latest) works just fine:

[   14.071134] Bluetooth: Core ver 2.22
[   14.071328] Bluetooth: HCI device and connection manager initialized
[   14.071352] Bluetooth: HCI socket layer initialized
[   14.071363] Bluetooth: L2CAP socket layer initialized
[   14.071404] Bluetooth: SCO socket layer initialized
[   14.397969] Bluetooth: HCI UART driver ver 2.3
[   14.402607] Bluetooth: HCI UART protocol H4 registered
[   14.407929] Bluetooth: HCI UART protocol BCSP registered
[   14.490109] Bluetooth: HCI UART protocol LL registered
[   14.497315] Bluetooth: HCI UART protocol Broadcom registered
[   14.565484] Bluetooth: HCI UART protocol QCA registered
[   14.573000] Bluetooth: HCI UART protocol Marvell registered
[   14.912586] Bluetooth: hci0: BCM: chip id 107
[   14.922423] Bluetooth: hci0: BCM: features 0x2f
[   14.928848] Bluetooth: hci0: BCM4345C0
[   14.928870] Bluetooth: hci0: BCM4345C0 (003.001.025) build 0000
[   14.946924] Bluetooth: hci0: BCM4345C0 'brcm/BCM4345C0.hcd' Patch
[   15.230121] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[   15.235649] Bluetooth: BNEP socket layer initialized
[   15.765508] Bluetooth: hci0: BCM: features 0x2f
[   15.771862] Bluetooth: hci0: BCM43455 37.4MHz Raspberry Pi 3+
[   15.777712] Bluetooth: hci0: BCM4345C0 (003.001.025) build 0342
[   15.802863] Bluetooth: MGMT ver 1.22

So now I am very interested how I have my known-good system working with the rpi4 kernel but I can't get it to boot with the normal kernel...

I haven't tried

taking your existing, working system (after taking a backup!) and deploy the minimal flake with nixos-rebuild

Is relying on being able to boot the previous generation a sufficient backup? 🤔

I hope we can work together to figure this out. Hopefully others will chime in if they know something or have any suggestions.

[FPtje]

I'm a newcomer to this issue. Today I was playing with my newly acquired Raspberry Pi 4B, 4GB and played around with this issue. I would like to confirm this bug with the current nixpkgs, and I would like to provide a summary of the current status:

My nixpkg revision is 5dc7114b7b256d217fe7752f1614be2514e61bb8. It's nixpkgs-unstable, pin updated at 27-11-2022.

I played with a couple of kernels. A summary is below:

Raspberry Pi Kernel

Following the wiki and the linked nix.dev article sets up an install using the generic aarch64 SD image. After following these guides, one ends up importing nixos-hardware.nixosModules.raspberry-pi-4 from the NixOS-hardware repo. This setup will use the Linux kernel as provided by the Raspberry foundation (attribute name pkgs.linuxPackages_rpi4).

This setup has the following problems:

• Bluetooth does not work. The controller is not found. One can run sudo btattach -B /dev/ttyAMA0 -P bcm to get one step closer to something working, but it is still broken, as described above.
• Audio does not work: an analog device is detected, though no sound plays through it regardless of volume settings.

Upstream kernel 5.15

One can use kernel 5.15, by setting boot.kernelPackages = pkgs.linuxPackages; (or pkgs.linuxPackages_5_15 to be precise) in the NixOS config (as of 5dc7114b7b256d217fe7752f1614be2514e61bb8). This changes the following:

• Most options from NixOS/nixos-hardware stop working. Specifically, most device tree overlays defined in raspberry-pi/4/... fail to apply. Luckily, most things should just work in the kernel itself
• Bluetooth works. I successfully connected to a bluetooth speaker and had audio work on it.
• Audio (jack) works. Audio plays through the jack.
• HDMI0 does not show anything beyond stage 2 boot, though HDMI1 works. This appears to be https://github.com/NixOS/nixpkgs/issues/179701
  • Setting the suggested hdmi_force_hotplug = 1 in config.txt made no real difference here.
• The maximum screen resolution for my screen is 1368x768x60hz. I suspect that this is because graphics are not officially supported on 5.15 yet. See this article for someone getting the V3D GPU driver to work on precisely this kernel.

Here is a (reduced) version of the config that works for me:

{ config, pkgs, lib, ... }:
{
  hardware = {
    bluetooth.enable = true;
    enableRedistributableFirmware = true;
    pulseaudio.enable = true;
    deviceTree.filter = "bcm2711-rpi-*.dtb";
  };

  boot = {
    # Bluetooth doesn't work with rpi4 kernel
    # https://github.com/NixOS/nixpkgs/issues/123725
    kernelPackages = pkgs.linuxPackages;
    # Not sure how much of this this is relevant
    initrd.availableKernelModules = [
      "usbhid"
      "usb_storage"
      "vc4"
      "pcie_brcmstb"      # required for the pcie bus to work
      "reset-raspberrypi" # required for vl805 firmware to load
    ];
    loader = {
      generic-extlinux-compatible.enable = true;
    };
  };

  fileSystems = {
    "/" = {
      device = "/dev/disk/by-label/NIXOS_SD";
      fsType = "ext4";
      options = [ "noatime" ];
    };
  };
}

Some elements taken from nixos-hardware. I copied those over manually because I load that repo in through a flake, which doesn't make for a nice snippet.

Upstream kernel 6.0.9

This kernel can be used by setting boot.kernelPackages = pkgs.linuxPackages_latest; (or pkgs.linuxPackages_6_0 to be precise). This kernel failed to boot to desktop, as the x-server started to SEGFAULT on boot.

Edit 28-11: interestingly, this article states that video driver support was merged for kernel version 6, but implies there are some bugs. That may explain the SEGFAULTs I'm seeing. I haven't looked further into this.

---

Kernels between 5.15 and 6.0.9 have dropped upstream support, and have been removed from nixpkgs. Therefore I haven't tried them.

Edit: I've added a link to this issue in the Wiki page: https://nixos.wiki/wiki/NixOS_on_ARM/Raspberry_Pi_4

[avieth]

One way to get bluetooth to work is by copying the firmware and kernel from a raspbian image and then hacking it into NixOS. Here's how.

[lilyball]

@avieth If I already have a configured raspberry pi, is there a way to update it in place with this?