Demi Marie Obenour <demiobenour@gmail.com> writes:

> This replaces the mdevd uevent daemon with systemd-udevd, which supports
> much more hardware and is therefore to be preferred for a full desktop
> environment.  Various Wayland compositors integrate with systemd-udevd,
> allowing them to discover devices as they appear rather than having to
> only use devices plugged in when the compositor is started.
> Additionally, systemd-udevd has quirks for various devices that are
> needed to support the wide variety of hardware end-users have.
>
> The dependency on /dev/dri/card0 being present is eliminated, and
> whatever devices the user has are now picked up by the compositor.  New
> dependencies are added to ensure that udev coldplug has finished before
> any non-trivial services are started.  systemd-udev-trigger.service runs
> 'udevadm trigger' and has Before=sysinit.target, so anything that is not
> an early boot service can assume 'udevadm trigger' has run.
>
> systemd-udevd doesn't set PATH to anything useful, presumably because
> under NixOS this is handled some other way.  Therefore, explicitly set
> it to /usr/bin in the scripts systemd-udevd calls.
>
> The /etc/mdev/listen and /etc/mdev/wait scripts are replaced by
> 'udevadm wait', so they are deleted.  The whole static-nodes target also
> goes away, as Linux handles that itself and systemd-udevd deals with
> autoloading.

Not quite right.  Linux does not create static nodes.  Userspace has to.
That's why we had a service for it.  (It sucks.)

> diff --git a/host/rootfs/image/etc/s6-rc/kvm/up b/host/rootfs/image/etc/s6-rc/kvm/up
> index c02e3f90245e005b98b4de8245a1863fb49c1158..a8436de58580f2a2a6f42bb69418a319f967df47 100644
> --- a/host/rootfs/image/etc/s6-rc/kvm/up
> +++ b/host/rootfs/image/etc/s6-rc/kvm/up
> @@ -1,4 +1,3 @@
>  # SPDX-License-Identifier: EUPL-1.2+
> -# SPDX-FileCopyrightText: 2023 Alyssa Ross <hi@alyssa.is>
> -
> -/etc/mdev/wait kvm
> +# SPDX-FileCopyrightText: 2025 Demi Marie Obenour <demiobenour@gmail.com>
> +udevadm wait /dev/kvm

Any reason now not to just inline this into the services that need to wait?

> diff --git a/host/rootfs/image/etc/s6-rc/systemd-udevd/run b/host/rootfs/image/etc/s6-rc/systemd-udevd/run
> new file mode 100644
> index 0000000000000000000000000000000000000000..2501680b69eb0060b651146dffb6b3a99640c6fb
> --- /dev/null
> +++ b/host/rootfs/image/etc/s6-rc/systemd-udevd/run
> @@ -0,0 +1,11 @@
> +#!/bin/execlineb -P
> +# SPDX-License-Identifier: EUPL-1.2+
> +# SPDX-FileCopyrightText: 2025 Demi Marie Obenour <demiobenour@gmail.com>
> +if { rm -f /run/sd-notify-wrapper/systemd-udevd }
> +background {
> +   s6-ipcserver-socketbinder -b0 -m -a 0600 /run/sd-notify-wrapper/systemd-udevd
> +   fdmove 1 3
> +   sd-notify-adapter
> +}
> +export NOTIFY_SOCKET /run/sd-notify-wrapper/systemd-udevd
> +exec -a systemd-udevd udevadm

How does systemd expect this to normally work?

> diff --git a/host/rootfs/image/etc/s6-rc/vm-env/contents b/host/rootfs/image/etc/s6-rc/vm-env/contents
> index 580795b1b02bb7a8dff7f872723c678141d4bb70..ed8b5c410adfc17f5bbc33932ac79d97bd7b3115 100644
> --- a/host/rootfs/image/etc/s6-rc/vm-env/contents
> +++ b/host/rootfs/image/etc/s6-rc/vm-env/contents
> @@ -2,4 +2,5 @@
>  # SPDX-FileCopyrightText: 2021 Alyssa Ross <hi@alyssa.is>
>  #
>  static-nodes
> +systemd-udevd-coldplug
>  weston

Shouldn't static-nodes be removed here as well, and the static-nodes
files deleted?

> diff --git a/host/rootfs/image/etc/udev/rules.d/99-spectrum.rules b/host/rootfs/image/etc/udev/rules.d/99-spectrum.rules
> new file mode 100644
> index 0000000000000000000000000000000000000000..ca91367529f39eebe009cc8acef782cf6a4516c1
> --- /dev/null
> +++ b/host/rootfs/image/etc/udev/rules.d/99-spectrum.rules
> @@ -0,0 +1,9 @@
> +# SPDX-License-Identifier: EUPL-1.2+
> +# SPDX-FileCopyrightText: 2025 Demi Marie Obenour <demiobenour@gmail.com>
> +
> +# systemd-udevd has a built-in module loading feature,
> +# but it seems to not work for some reason or another.
> +# This works.
> +ACTION!="remove", ENV{MODALIAS}!="", RUN+="/usr/bin/modprobe -q $env{MODALIAS}"
> +# systemd-udevd unsets PATH, so fix that.
> +ACTION!="remove", ENV{PCI_CLASS}=="2????", RUN+="/usr/bin/env PATH=/usr/bin /usr/libexec/net-add"

This is such a weird behavior.  Do we know why it does that?

> diff --git a/host/rootfs/image/usr/bin/vm-start b/host/rootfs/image/usr/bin/vm-start
> index 67480e5215d8a8260ce3f03c67f71ba8f210c291..9725ef5ec549ff191606282a7b0ae56838f53f03 100755
> --- a/host/rootfs/image/usr/bin/vm-start
> +++ b/host/rootfs/image/usr/bin/vm-start
> @@ -2,7 +2,7 @@
>  # SPDX-License-Identifier: EUPL-1.2+
>  # SPDX-FileCopyrightText: 2022-2023, 2025 Alyssa Ross <hi@alyssa.is>
>  
> -foreground { s6-rc -bu change vm-env }
> +foreground { s6-rc -bu change weston }
>  
>  foreground {
>    redirfd -w 2 /dev/null

Why?