Commit 0f174b35 authored by Takashi Iwai's avatar Takashi Iwai

ALSA: usb-audio: Add mute TLV for playback volumes on C-Media devices

C-Media devices (at least some models) mute the playback stream when
volumes are set to the minimum value.  But this isn't informed via TLV
and the user-space, typically PulseAudio, gets confused as if it's
still played in a low volume.

This patch adds the new flag, min_mute, to struct usb_mixer_elem_info
for indicating that the mixer element is with the minimum-mute volume.
This flag is set for known C-Media devices in
snd_usb_mixer_fu_apply_quirk() in turn.

Cc: <>
Signed-off-by: default avatarTakashi Iwai <>
parent a8e800fe
......@@ -542,6 +542,8 @@ int snd_usb_mixer_vol_tlv(struct snd_kcontrol *kcontrol, int op_flag,
if (size < sizeof(scale))
return -ENOMEM;
if (cval->min_mute)
scale[2] = cval->dBmin;
scale[3] = cval->dBmax;
if (copy_to_user(_tlv, scale, sizeof(scale)))
......@@ -64,6 +64,7 @@ struct usb_mixer_elem_info {
int cached;
int cache_val[MAX_CHANNELS];
u8 initialized;
u8 min_mute;
void *private_data;
......@@ -1878,6 +1878,12 @@ void snd_usb_mixer_fu_apply_quirk(struct usb_mixer_interface *mixer,
if (unitid == 7 && cval->control == UAC_FU_VOLUME)
snd_dragonfly_quirk_db_scale(mixer, cval, kctl);
/* lowest playback value is muted on C-Media devices */
case USB_ID(0x0d8c, 0x000c):
case USB_ID(0x0d8c, 0x0014):
if (strstr(kctl->, "Playback"))
cval->min_mute = 1;
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