Re: [RFC]sound:usb:mixer.c: Solving 'Generic AB13X USB Audio' Unlikely volume range.

[Takashi Iwai]

On Mon, 29 Sep 2025 15:37:52 +0200,
Sidharth Seela wrote:
> 
> Dear Maintainers,
> I am using a generic "boat" make earphones, which are too loud across
> different systems with eg: iOS, macOS, Debian Linux. And hence I believe
> the issue is not with a driver but the headphones.
> 
> After connecting this device to laptop I get the following in dmesg logs:
> 	usb 1-5: New USB device found, idVendor=001f, idProduct=0b21, bcdDevice= 1.00
> 	usb 1-5: New USB device strings: Mfr=1, Product=2, SerialNumber=3
> 	usb 1-5: Product: AB13X USB Audio
> 	usb 1-5: Manufacturer: Generic
> 	usb 1-5: SerialNumber: 20210726905926
> 	usb 1-5: Warning! Unlikely big volume range (=11520), cval->res is probably wrong.
> 	usb 1-5: [2] FU [PCM Playback Volume] ch = 2, val = -11520/0/1
> 	usb 1-5: Warning! Unlikely big volume range (=8191), cval->res is probably wrong.
> 	usb 1-5: [5] FU [Mic Capture Volume] ch = 1, val = 0/8191/1
> 
> By using pavucontrol, I am able to get fair sound, after reducing 17dB in
> Analog Stereo Output and reducing 6dB in Digital Stereo Output.
> 
> I believe this issue could be solved by adding a quirk patch to
> sound/usb/mixer.c:1096 (/* volume control quriks */).

An oft-seen firmware bug is that it provides the wrong mixer range
that confuses the driver.  USB audio firmware should provide the above
volume range in 1/256 dB level.

Try to figure out the volume level and you'd need to hard-code the
actual volume range there for your device.


Takashi