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ALSA: usb-audio: Improve volume range checks

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Currently the volume range check is only meant to discover quirky
microphone on webcam devices and facing these issues:

- The check is only meaningful for dB volume, but it doesn't check if
  the TLV callback is the corresponding one
- A common quirky pattern "val = 0/100/1" doesn't trigger any warning
- Some modern devices trigger the check, but they are legit
- The warning message doesn't apply to some quirky messages with linear
  volume
- The term "range" in the warning message is confusing. At readers'
  first glance it should be (max - min), but it turns out to be
  ((max - min) / res)

Solve these issues by improving the checking logic to:

- Ignore mixers with non-dB TLV
- Warn on unlikely small volume ranges (max - min < 256)
- Add some heuristics to determine if the volume range is unlikely big
- Rephrase the warning message to mention linear volume
- Rephrase the warning message in correct wording

Signed-off-by: Rong Zhang <i@rong.moe>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20260303194805.266158-4-i@rong.moe
This commit is contained in:
Rong Zhang 2026-03-04 03:47:58 +08:00 committed by Takashi Iwai
parent 1060dbbbb2
commit 52dc4b190a
1 changed files with 48 additions and 6 deletions
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54
sound/usb/mixer.c
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@ -1664,20 +1664,62 @@ static bool check_insane_volume_range(struct usb_mixer_interface *mixer,
struct snd_kcontrol *kctl,
struct usb_mixer_elem_info *cval)
{
int range = (cval->max - cval->min) / cval->res;
int range, steps, threshold;
/*
* Are there devices with volume range more than 255? I use a bit more
* to be sure. 384 is a resolution magic number found on Logitech
* devices. It will definitively catch all buggy Logitech devices.
* If a device quirk has overrode our TLV callback, no warning should
* be generated since our checks are only meaningful for dB volume.
*/
if (range > 384) {
if (!(kctl->vd[0].access & SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK) ||
kctl->tlv.c != snd_usb_mixer_vol_tlv)
return false;
/*
* Meaningless volume control capability (<1dB). This should cover
* devices mapping their volume to val = 0/100/1, which are very likely
* to be quirky.
*/
range = cval->max - cval->min;
if (range < 256) {
usb_audio_warn(mixer->chip,
"Warning! Unlikely big volume range (=%u), cval->res is probably wrong.",
"Warning! Unlikely small volume range (=%u), linear volume or custom curve?",
range);
return true;
}
steps = range / cval->res;
/*
* There are definitely devices with ~20,000 ranges (e.g., HyperX Cloud
* III with val = -18944/0/1), so we use some heuristics here:
*
* min < 0 < max: Attenuator + amplifier? Likely to be sane
*
* min < 0 = max: DSP? Voltage attenuator with FW conversion to dB?
* Likely to be sane
*
* min < max < 0: Measured values? Neutral
*
* min = 0 < max: Oversimplified FW conversion? Linear volume? Likely to
* be quirky (e.g., MV-SILICON)
*
* 0 < min < max: Amplifier with fixed gains? Likely to be quirky
* (e.g., Logitech webcam)
*/
if (cval->min < 0 && 0 <= cval->max)
threshold = 24576; /* 65535 * (3 / 8) */
else if (cval->min < cval->max && cval->max < 0)
threshold = 1024;
else
threshold = 384;
if (steps > threshold) {
usb_audio_warn(mixer->chip,
"Warning! Unlikely big volume step count (=%u), linear volume or wrong cval->res?",
steps);
return true;
}
return false;
}