udev: Skip audio power_save override for AMD HDA controllers (#204)

[ptr1337]

On AMD Strix/Krackan laptops, the audio controller shares a PCI bus with the GPU. Forcing power_save=0 keeps the codec in D0 state, causing audible electrical interference/buzzing during GPU and NVMe activity.

Restrict the power_save=0 override to Intel HDA controllers (vendor 0x8086), which are the hardware affected by the audio popping that this rule was designed to prevent. AMD HDA controllers now keep their default power_save behavior, allowing them to suspend when idle and eliminating the EMI noise.

Also guard the AC/battery power_supply rules on the flag file existence so they only fire on systems where the boot rule actually applied.

Closes #204

[Copilot]

Pull request overview

Updates the snd_hda_intel udev power-management behavior to avoid forcing power_save=0 on AMD HDA controllers (reported to cause EMI/buzzing on Strix/Krackan-class systems), while keeping the original “prevent popping” behavior targeted at Intel HDA hardware.

Changes:

• Restrict the power_save=0 override to Intel HDA controllers via ATTRS{vendor}=="0x8086".
• Gate AC/battery power_supply handlers on the presence of the /run/udev/snd-hda-intel-powersave state file so they only run on systems where the boot-time rule matched.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

The RUN script always touches /run/udev/snd-hda-intel-powersave before the battery check. If the system is already discharging at boot, this leaves the file empty (no saved value), which can later be treated as a valid value by the AC/battery handlers. Consider only creating the file when you also write the saved parameter value (or always write the current power_save into it regardless of charging state).

Suggested change

	RUN+="/usr/bin/bash -c 'touch /run/udev/snd-hda-intel-powersave; \
	[[ $$(cat /sys/class/power_supply/BAT0/status 2>/dev/null) != \"Discharging\" ]] && \
	echo $$(cat /sys/module/snd_hda_intel/parameters/power_save) > /run/udev/snd-hda-intel-powersave && \
	RUN+="/usr/bin/bash -c 'echo $$(cat /sys/module/snd_hda_intel/parameters/power_save) > /run/udev/snd-hda-intel-powersave; \
	[[ $$(cat /sys/class/power_supply/BAT0/status 2>/dev/null) != \"Discharging\" ]] && \

[Copilot]

cat /run/udev/snd-hda-intel-powersave 2>/dev/null || echo 10 does not fall back when the file exists but is empty (because cat still exits 0). With an empty saved-value file, this expands to an empty string and can attempt to write an invalid value to /sys/module/snd_hda_intel/parameters/power_save. Handle the empty-file case explicitly (e.g., validate the value is non-empty/numeric before writing, otherwise use a default).

Suggested change

	RUN+="/usr/bin/bash -c 'echo $$(cat /run/udev/snd-hda-intel-powersave 2>/dev/null || \
	echo 10) > /sys/module/snd_hda_intel/parameters/power_save'"
	RUN+="/usr/bin/bash -c 'val=$$(cat /run/udev/snd-hda-intel-powersave 2>/dev/null); \
	case $$val in (""|*[!0-9]*) val=10 ;; esac; \
	echo $$val > /sys/module/snd_hda_intel/parameters/power_save'"

[ventureoo]

Please remove also fallback as 10 value in the cat, since it's not needed with TEST