Public bug reported:
Summary: After long-term testing of Ubuntu 24.04.2 LTS on the Apple iMac
18,3 (27", 2017), I’ve concluded that the system contains all necessary
drivers — located in the kernel and in packages like linux-modules-extra
— but their behavior is unpredictable. Ubuntu often fails to load,
assign, or correctly activate them during installation. There are
ongoing issues affecting sound, graphics drivers, internal microphone,
and webcam functionality.
📋 Observed issues:
Audio – Cirrus Logic CS8409 / CS42L83
The snd-hda-codec-cs8409 module is available, but not properly
initialized.
The system shows “Dummy Output” and audio doesn’t work without manual
patching.
Internal microphone (NID 0x45) is detected but inactive.
Missing alsa-ucm-conf profile → no devices or input streams shown in
GUI.
Graphics – AMD Radeon (AMDGPU)
On installation, the system loads Mesa fallback driver → incorrect
resolution and audio instability.
Installing AMDGPU driver 25.10.1 resolved both resolution and audio
subsystem interaction issues.
Webcam (Apple internal)
Camera launches via cheese, but turns off abruptly during recording.
Likely related to power delivery, ACPI events, or missing initialization
routines.
🧪 Diagnostics & insights:
Upstream kernel 6.16-rc6 contains working DMIC initialization for microphone
(patch_cs8409.c).
Ubuntu kernel 6.11 includes the CS8409 module, but lacks full microphone
functionality.
Drivers exist, but:
Are not loaded automatically during installation.
Are not assigned correctly to hardware.
Do not activate input/output devices without manual effort.
📎 Attached information:
Diagnostic logs from alsa-info.sh, dmesg, arecord, pw-dump
Technical analysis of upstream kernel code (DMIC logic – NID 0x45)
Attached .txt file containing hardware documentation extracted from
Apple BootCamp: Retrieved from system path: marek-
havlik@mahav:~/Plocha/WindowsSupport$ ls '$WinPEDriver$' BootCamp The
file includes component identifiers (CS8409, CS42L83, AMDGPU, webcam)
helpful for developing UCM profiles and driver assignments.
🛠️ Suggestions to the development team:
Include a proper UCM profile for CS8409 / CS42L83 in alsa-ucm-conf
Backport DMIC activation patch from kernel 6.16 to Ubuntu 6.11+
Improve hardware detection logic to:
Load modules without manual intervention
Automatically match drivers during Ubuntu installation
Prefer AMDGPU over Mesa fallback when Apple hardware is detected
Investigate webcam and microphone behavior — possibly caused by ACPI,
UVC or missing init triggers
Note: Due to recurring issues, I no longer actively use Ubuntu on this
system. However, I am happy to assist with testing, validating patches,
or helping with a DKMS implementation. I have access to the real
hardware (iMac18,3) as well as the original BootCamp documentation from
macOS.
Thank you for your work — I hope these insights help improve Apple
hardware support on Ubuntu. – Marek (mahav-t)
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2119402
Title:
)Persistent driver issues on iMac 18,3 (27", 2017)
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