Re: [PATCH v2] ALSA: hda/conexant: fix FEVM FA880 PRO internal mic mux

[周Ocean]

Hi Takashi,

To be honest, I'm not an expert on the low-level hardware design of
this codec, but I can confirm that the internal microphone only works
normally when we apply this patch.

I realized why the previous two dumps were identical: the user-space
audio server (PipeWire) automatically restored the routing and
switched NID 0x14 to NID 0x1e (index 3) at runtime, masking the actual
boot defaults.

This time, I stopped PipeWire entirely, reloaded the stock driver, and
captured the true hardware defaults. Please find the new logs
attached:

1. alsa-info-raw-defaults.txt.gz (Stock driver, pure hardware defaults):
Here, NID 0x14 actually defaults to NID 0x1b (index 1, Rear Mic) on boot:
   Connection: 4
      0x1a 0x1b* 0x1d 0x1e

2. alsa-info-with-patch.txt.gz (Patched driver):
Here, the quirk forces it to NID 0x1e (index 3, Internal Mic) at initialization:
   Connection: 4
      0x1a 0x1b 0x1d 0x1e*

Without the patch, testing the microphone in the stock driver yields a
loud buzzing/humming noise (typical of a floating/unconnected input
pin on NID 0x1b) with only a very faint sound when tapping the chassis
(due to signal crosstalk/leakage from NID 0x1e to NID 0x1b). Even if
PipeWire switches the connection to 0x1e at runtime later, it fails to
record normal sound.

Applying the quirk at ACT_INIT ensures NID 0x14 is correctly mapped to
the physical internal mic pin (0x1e) from boot, resolving the floating
pin noise and restoring mic capture to a normal level.

Thanks,
Ocean

Takashi Iwai <tiwai@xxxxxxx> 于2026年6月4日周四 16:12写道：
>
> On Wed, 03 Jun 2026 17:08:04 +0200,
> 周Ocean wrote:
> >
> > Hi Takashi,
> >
> > Due to size limits on the mailing list, I've compressed the alsa-info
> > outputs. Please find them attached.
> >
> > 1. alsa-info-with-patch.txt.gz:
> > Generated on LTS kernel (6.18.33) with the patch applied via DKMS.
> > Under this state, the internal microphone works.
> >
> > 2. alsa-info-without-patch.txt.gz:
> > Generated on the same kernel with the DKMS patch uninstalled (stock
> > driver). The internal microphone does not work in this state.
>
> Thanks.  But I couldn't see the difference about NID 0x14: both with
> and without patch show it's connecting to NID 0x1e (index #3).
> What am I missing?
>
>
> Takashi

Attachment: alsa-info-with-patch.txt.gz
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Attachment: alsa-info-raw-defaults.txt.gz
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