Re: [PATCH v4 3/3] Run PipeWire and WirePlumber in the VMs

[Demi Marie Obenour <demiobenour@gmail.com>]

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On 7/18/25 07:27, Alyssa Ross wrote:
> Demi Marie Obenour <demiobenour@gmail.com> writes:
> 
>> WirePlumber is completely overkill as a session manager here, and
>> ideally a trivial session manager would be used instead.  I did build a
>> Spectrum OS image and found that PipeWire and WirePlumber both
>> successfully started.  PipeWire is configured to listen on the
>> PulseAudio socket, so PulseAudio compatibility works.  This does inject
>> a large number of completely unnecessary files into the VM, notably for
>> libcamera and Bluetooth support.
>>
>> Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
>> ---
>>
>> Notes:
>>     I tested this with QEMU virtio-sound, but I am not sure if the paramters
>>     are correct.  In particular, the sample rate might well be wrong.
>>
>>  img/app/Makefile                              |  28 +-
>>  img/app/default.nix                           |  18 +
>>  img/app/etc/pipewire/pipewire.conf            | 291 ++++++++
>>  .../etc/s6-rc/app/dependencies.d/directories  |   0
>>  .../app/dependencies.d/directories.license    |   2 +
>>  .../etc/s6-rc/app/dependencies.d/wireplumber  |   0
>>  .../app/dependencies.d/wireplumber.license    |   2 +
>>  .../etc/s6-rc/dbus/dependencies.d/directories |   0
>>  .../dbus/dependencies.d/directories.license   |   2 +
>>  img/app/etc/s6-rc/directories/type            |   1 +
>>  img/app/etc/s6-rc/directories/type.license    |   2 +
>>  img/app/etc/s6-rc/directories/up              |  11 +
>>  .../s6-rc/pipewire/dependencies.d/directories |   0
>>  .../dependencies.d/directories.license        |   2 +
>>  img/app/etc/s6-rc/pipewire/notification-fd    |   1 +
>>  .../s6-rc/pipewire/notification-fd.license    |   2 +
>>  img/app/etc/s6-rc/pipewire/run                |  20 +
>>  img/app/etc/s6-rc/pipewire/type               |   1 +
>>  img/app/etc/s6-rc/pipewire/type.license       |   2 +
>>  .../dependencies.d/directories                |   0
>>  .../dependencies.d/directories.license        |   2 +
>>  img/app/etc/s6-rc/wayland-proxy-virtwl/run    |  11 -
>>  .../etc/s6-rc/wireplumber/dependencies.d/dbus |   0
>>  .../wireplumber/dependencies.d/dbus.license   |   2 +
>>  .../s6-rc/wireplumber/dependencies.d/pipewire |   0
>>  .../dependencies.d/pipewire.license           |   2 +
>>  img/app/etc/s6-rc/wireplumber/run             |   4 +
>>  img/app/etc/s6-rc/wireplumber/type            |   1 +
>>  img/app/etc/s6-rc/wireplumber/type.license    |   2 +
>>  img/app/etc/wireplumber/wireplumber.conf      | 676 ++++++++++++++++++
> 
> The PipeWire and WirePlumber config files are still very big.  Is it
> really not possible to make them smaller and rely on defaults where
> possible?  With a whole big config like this, it's difficult to see what
> Spectrum-specific stuff is going on.

Both of these files are *smaller* than their upstream counterparts.
The main Spectrum-specific stuff is:

- Nodes are statically set up.  This is because PipeWire relies on
  udev to enumerate device nodes, and Spectrum VMs don't have udev.

- A lot of stuff in the upstream configuration files has been
  removed.  Spectrum's configs should be *smaller* than their
  upstream counterparts.

Neither PipeWire nor WirePlumber has much in the way of a default
configuration.  Without a configuration file, neither PipeWire nor
WirePlumber does anything useful.  Overriding the defaults and
using the upstream configuration file might be possible, but it
seemed unlikely when I looked.  Spectrum VMs are more like
embedded systems than the desktop systems the defaults are made
for.

I recommend not including any of the upstream configuration
files and only an allowlist of SPA plugins and PipeWire and
WirePlumber modules.  Stuff like Bluetooth can also be excluded.
Just because upstream nixpkgs pulls it in as a dependency does
not mean the configuration in the VM actually needs it.
Ideally, the various plugins and modules would all be separate
build outputs with their own dependencies, and ‘pipewire’ and
‘wireplumber’ would be meta-packages that pull in all of them.

>> diff --git a/img/app/default.nix b/img/app/default.nix
>> index 740643ac41f6473cdb6f6b0fd1f5f47f4493240d..8c469ee5b9a672bf6504600b09ff1f57fb87f2d9 100644
>> --- a/img/app/default.nix
>> +++ b/img/app/default.nix
>> @@ -26,6 +26,20 @@ let
>>            CONFIG_FEATURE_IP_ROUTE y
>>            CONFIG_INIT n
>>            CONFIG_IP y
>> +          CONFIG_FACTOR n
>> +          CONFIG_FOLD n
>> +          CONFIG_LSSCSI n
>> +          CONFIG_NANDWRITE n
>> +          CONFIG_NANDDUMP n
>> +          CONFIG_RAIDAUTORUN n
>> +          CONFIG_RFKILL n
>> +          CONFIG_UBIATTACH n
>> +          CONFIG_UBIDETACH n
>> +          CONFIG_UBIMKVOL n
>> +          CONFIG_UBIRMVOL n
>> +          CONFIG_UBIRSVOL n
>> +          CONFIG_UBIUPDATEVOL n
>> +          CONFIG_UBIRENAME n
> 
> Do these all conflict with PipeWire/WirePlumber/PulseAudio??

Nope.  This should have been a separate patch.  It is purely
to save disk space and build time by excluding stuff that we
definitely have no use for.
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)

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