[PATCH 0/2] ALSA: usb-audio: Support for Feaulle Rainbow

[Rong Zhang]

Feaulle Rainbow is a wired USB-C dynamic in-ear monitor (IEM) featuring
active noise cancellation (ANC).

The supported sample rates are 48000Hz and 96000Hz at 16bit or 24bit,
but it does not support reading the current sample rate and results in
an error message printed to kmsg. Set QUIRK_FLAG_GET_SAMPLE_RATE to skip
the sample rate check.

Its playback mixer reports val = -15360/0/128. Setting -15360 (-60dB)
mutes the playback, so QUIRK_FLAG_MIXER_PLAYBACK_MIN_MUTE is needed.

Its Mic Capture Volume mixer is sticky (accepts SET_CUR but do
absolutely nothing). Registering it confuses userspace and results in
ineffective volume control.

Patch 1 adds a quirk table entry matching VID/PID=0x0e0b/0xfa01 and
applying the mentioned quirk flags, so that it can work properly.

Patch 2 checks if a volume control mixer is sticky by setting the volume
to the maximum or minimum value, and prevent the mixer from being
registered accordingly.

Quirky device sample:

  usb 7-1: New USB device found, idVendor=0e0b, idProduct=fa01, bcdDevice= 1.00
  usb 7-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
  usb 7-1: Product: Feaulle Rainbow
  usb 7-1: Manufacturer: Generic
  usb 7-1: SerialNumber: 20210726905926

Signed-off-by: Rong Zhang <i@xxxxxxxx>
---
Rong Zhang (2):
      ALSA: usb-audio: Add quirk flags for Feaulle Rainbow
      ALSA: usb-audio: Do not expose sticky volume control mixers

 sound/usb/mixer.c  | 37 +++++++++++++++++++++++++++++++++++--
 sound/usb/quirks.c |  2 ++
 2 files changed, 37 insertions(+), 2 deletions(-)
---
base-commit: 292286b2d229fb732421429b027d38ac3f969383
change-id: 20260403-feaulle-rainbow-fb6e2db837a4

Thanks,
Rong