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

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.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=196669


Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent a8e800fe

sound/usb/mixer.c

+2 −0
Original line number Diff line number Diff line
@@ -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[0] = SNDRV_CTL_TLVT_DB_MINMAX_MUTE;

	scale[2] = cval->dBmin;

	scale[3] = cval->dBmax;

	if (copy_to_user(_tlv, scale, sizeof(scale)))

sound/usb/mixer.h

+1 −0
Original line number Diff line number Diff line
@@ -64,6 +64,7 @@ struct usb_mixer_elem_info { 
	int cached;

	int cache_val[MAX_CHANNELS];

	u8 initialized;

	u8 min_mute;

	void *private_data;

};

sound/usb/mixer_quirks.c

+6 −0
Original line number Diff line number Diff line
@@ -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);

		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;

	}

}