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

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commit 0f174b3525 upstream.

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.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=196669
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Takashi Iwai 2017-08-16 14:18:37 +02:00 • committed by Greg Kroah-Hartman
commit 669c8ab896
3 changed files with 9 additions and 0 deletions
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2
sound/usb/mixer.c
View file

@ -541,6 +541,8 @@ int snd_usb_mixer_vol_tlv(struct snd_kcontrol *kcontrol, int op_flag,
if (size < sizeof(scale))
return -ENOMEM;
if (cval->min_mute)
scale[0] = SNDRV_CTL_TLVT_DB_MINMAX_MUTE;
scale[2] = cval->dBmin;
scale[3] = cval->dBmax;
if (copy_to_user(_tlv, scale, sizeof(scale)))

1
sound/usb/mixer.h
View file

@ -64,6 +64,7 @@ struct usb_mixer_elem_info {
int cached;
int cache_val[MAX_CHANNELS];
u8 initialized;
u8 min_mute;
void *private_data;
};

6
sound/usb/mixer_quirks.c
View file

@ -1873,6 +1873,12 @@ 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);
break;
/* lowest playback value is muted on C-Media devices */
case USB_ID(0x0d8c, 0x000c):
case USB_ID(0x0d8c, 0x0014):
if (strstr(kctl->id.name, "Playback"))
cval->min_mute = 1;
break;
}
}