Re: [PATCH v3 2/2] host/rootfs: Switch to systemd-udevd

[Alyssa Ross <hi@alyssa.is>]

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

> On 10/1/25 10:39, Alyssa Ross wrote:
>> 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.
>> 
>> Just want to note that this implementation currently doesn't, because it
>> doesn't install the hardware database.  (I noticed this while debugging
>> the modprobe thing.)
>
> Nice catch.  Thank you!
>
>> I was able to get it to work with the following diff.  I don't think it
>> needs to be in this commit, so I'll just add this separately once we
>> have the basic udev implementation in, but I'm posting it here now so we
>> don't end up duplicating work. :)
>> 
>> diff --git a/host/rootfs/default.nix b/host/rootfs/default.nix
>> index 8abe108..b8e72f2 100644
>> --- a/host/rootfs/default.nix
>> +++ b/host/rootfs/default.nix
>> @@ -84,6 +84,15 @@ let
>>    usrPackages = [
>>      appvm kernel.modules firmware kmod kmod.lib
>>      netvm mesa dejavu_fonts westonLite
>> +
>> +    (runCommand "hwdb.bin" {
>> +      nativeBuildInputs = [ systemd ];
>> +    } ''
>> +      mkdir -p $out/lib/systemd/hwdb etc/udev
>> +      cp -R ${systemd}/lib/udev/hwdb.d etc/udev
>> +      systemd-hwdb update -sr .
>> +      mv etc/udev/hwdb.bin $out/lib/systemd/hwdb
>> +    '')
>>    ];
>>  
>>    appvms = {
>
> Could this just be a symlink?

Oh, probably.  Although I wonder if we want to move away from explicit
symlinks, because that's what created the problem where it's hard for
you to add stuff to /usr/lib…

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