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ALSA: usb-audio: Add QUIRK_FLAG_MIXER_{PLAYBACK,CAPTURE}_LINEAR_VOL

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Some quirky devices tune their volume by linearly tuning the voltage
level (linear volume). In other words, such devices has a linear TLV
mapping of DECLARE_TLV_DB_LINEAR(scale, TLV_DB_GAIN_MUTE, 0).

Add quirk flags MIXER_PLAYBACK_LINEAR_VOL and MIXER_CAPTURE_LINEAR_VOL
to represent this case respectively for playback and capture mixers.

No functional change intended.

Signed-off-by: Rong Zhang <i@rong.moe>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20260303194805.266158-7-i@rong.moe
This commit is contained in:
Rong Zhang
2026-03-04 03:48:01 +08:00
committed by Takashi Iwai
parent b13031ca11
commit 3787a6a10e
4 changed files with 55 additions and 0 deletions
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7
Documentation/sound/alsa-configuration.rst
View File

@@ -2376,6 +2376,13 @@ quirk_flags
Skip the probe-time interface setup (usb_set_interface,
init_pitch, init_sample_rate); redundant with
snd_usb_endpoint_prepare() at stream-open time
* bit 27: ``mixer_playback_linear_vol``
Set linear volume mapping for devices where the playback volume
control value is mapped to voltage (instead of dB) level linearly.
In short: ``x(raw) = (raw - raw_min) / (raw_max - raw_min)``;
``V(x) = k * x``; ``dB(x) = 20 * log10(x)``. Overrides bit 24
* bit 28: ``mixer_capture_linear_vol``
Similar to bit 27 but for capture streams. Overrides bit 25
This module supports multiple devices, autoprobe and hotplugging.

34
sound/usb/mixer_quirks.c
View File

@@ -4634,6 +4634,25 @@ triggered:
usb_audio_dbg(chip, "something wrong in kctl name %s\n", id->name);
}
static void snd_usb_mixer_fu_quirk_linear_scale(struct usb_mixer_interface *mixer,
struct usb_mixer_elem_info *cval,
struct snd_kcontrol *kctl)
{
static const DECLARE_TLV_DB_LINEAR(scale, TLV_DB_GAIN_MUTE, 0);
if (cval->min_mute) {
/*
* We are clearing SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK,
* resulting in min_mute being a no-op.
*/
usb_audio_warn(mixer->chip, "LINEAR_VOL overrides MIN_MUTE\n");
}
kctl->tlv.p = scale;
kctl->vd[0].access |= SNDRV_CTL_ELEM_ACCESS_TLV_READ;
kctl->vd[0].access &= ~SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK;
}
void snd_usb_mixer_fu_apply_quirk(struct usb_mixer_interface *mixer,
struct usb_mixer_elem_info *cval, int unitid,
struct snd_kcontrol *kctl)
@@ -4660,6 +4679,21 @@ void snd_usb_mixer_fu_apply_quirk(struct usb_mixer_interface *mixer,
"applying capture min mute quirk\n");
cval->min_mute = 1;
}
if (mixer->chip->quirk_flags & QUIRK_FLAG_MIXER_PLAYBACK_LINEAR_VOL)
if (cval->control == UAC_FU_VOLUME && strstr(kctl->id.name, "Playback")) {
usb_audio_info(mixer->chip,
"applying playback linear volume quirk\n");
snd_usb_mixer_fu_quirk_linear_scale(mixer, cval, kctl);
}
if (mixer->chip->quirk_flags & QUIRK_FLAG_MIXER_CAPTURE_LINEAR_VOL)
if (cval->control == UAC_FU_VOLUME && strstr(kctl->id.name, "Capture")) {
usb_audio_info(mixer->chip,
"applying capture linear volume quirk\n");
snd_usb_mixer_fu_quirk_linear_scale(mixer, cval, kctl);
}
/* ALSA-ify some Plantronics headset control names */
if (USB_ID_VENDOR(mixer->chip->usb_id) == 0x047f &&
(cval->control == UAC_FU_MUTE || cval->control == UAC_FU_VOLUME))

2
sound/usb/quirks.c
View File

@@ -2543,6 +2543,8 @@ static const char *const snd_usb_audio_quirk_flag_names[] = {
QUIRK_STRING_ENTRY(MIXER_PLAYBACK_MIN_MUTE),
QUIRK_STRING_ENTRY(MIXER_CAPTURE_MIN_MUTE),
QUIRK_STRING_ENTRY(SKIP_IFACE_SETUP),
QUIRK_STRING_ENTRY(MIXER_PLAYBACK_LINEAR_VOL),
QUIRK_STRING_ENTRY(MIXER_CAPTURE_LINEAR_VOL),
NULL
};

12
sound/usb/usbaudio.h
View File

@@ -228,6 +228,14 @@ extern bool snd_usb_skip_validation;
* Skip the probe-time interface setup (usb_set_interface,
* init_pitch, init_sample_rate); redundant with
* snd_usb_endpoint_prepare() at stream-open time
* QUIRK_FLAG_MIXER_PLAYBACK_LINEAR_VOL
* Set linear volume mapping for devices where the playback volume control
* value is mapped to voltage (instead of dB) level linearly. In short:
* x(raw) = (raw - raw_min) / (raw_max - raw_min); V(x) = k * x;
* dB(x) = 20 * log10(x). Overrides QUIRK_FLAG_MIXER_PLAYBACK_MIN_MUTE
* QUIRK_FLAG_MIXER_CAPTURE_LINEAR_VOL
* Similar to QUIRK_FLAG_MIXER_PLAYBACK_LINEAR_VOL, but for capture streams.
* Overrides QUIRK_FLAG_MIXER_CAPTURE_MIN_MUTE
*/
enum {
@@ -258,6 +266,8 @@ enum {
QUIRK_TYPE_MIXER_PLAYBACK_MIN_MUTE = 24,
QUIRK_TYPE_MIXER_CAPTURE_MIN_MUTE = 25,
QUIRK_TYPE_SKIP_IFACE_SETUP = 26,
QUIRK_TYPE_MIXER_PLAYBACK_LINEAR_VOL = 27,
QUIRK_TYPE_MIXER_CAPTURE_LINEAR_VOL = 28,
/* Please also edit snd_usb_audio_quirk_flag_names */
};
@@ -290,5 +300,7 @@ enum {
#define QUIRK_FLAG_MIXER_PLAYBACK_MIN_MUTE QUIRK_FLAG(MIXER_PLAYBACK_MIN_MUTE)
#define QUIRK_FLAG_MIXER_CAPTURE_MIN_MUTE QUIRK_FLAG(MIXER_CAPTURE_MIN_MUTE)
#define QUIRK_FLAG_SKIP_IFACE_SETUP QUIRK_FLAG(SKIP_IFACE_SETUP)
#define QUIRK_FLAG_MIXER_PLAYBACK_LINEAR_VOL QUIRK_FLAG(MIXER_PLAYBACK_LINEAR_VOL)
#define QUIRK_FLAG_MIXER_CAPTURE_LINEAR_VOL QUIRK_FLAG(MIXER_CAPTURE_LINEAR_VOL)
#endif /* __USBAUDIO_H */