ALSA: usb-audio: Add mute TLV for playback volumes on C-Media devices (0f174b35) · Commits · 戴 / test

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:

Takashi Iwai <tiwai@suse.de>

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;
		}
		}

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