linux-kernel - [PATCH AUTOSEL 5.8 36/63] ALSA: usb-audio: ignore broken processing/extension unit

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Date:   Mon, 24 Aug 2020 12:34:36 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Tom Yan <tom.ty89@...il.com>, Takashi Iwai <tiwai@...e.de>,
        Sasha Levin <sashal@...nel.org>, alsa-devel@...a-project.org
Subject: [PATCH AUTOSEL 5.8 36/63] ALSA: usb-audio: ignore broken processing/extension unit

From: Tom Yan <tom.ty89@...il.com>

[ Upstream commit d8d0db7bb358ef65d60726a61bfcd08eccff0bc0 ]

Some devices have broken extension unit where getting current value
doesn't work. Attempt that once when creating mixer control for it. If
it fails, just ignore it, so that it won't cripple the device entirely
(and/or make the error floods).

Signed-off-by: Tom Yan <tom.ty89@...il.com>
Link: https://lore.kernel.org/r/5f3abc52.1c69fb81.9cf2.fe91@mx.google.com
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 sound/usb/mixer.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index eab0fd4fd7c33..e0b7174c10430 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -2367,7 +2367,7 @@ static int build_audio_procunit(struct mixer_build *state, int unitid,
 	int num_ins;
 	struct usb_mixer_elem_info *cval;
 	struct snd_kcontrol *kctl;
-	int i, err, nameid, type, len;
+	int i, err, nameid, type, len, val;
 	const struct procunit_info *info;
 	const struct procunit_value_info *valinfo;
 	const struct usbmix_name_map *map;
@@ -2470,6 +2470,12 @@ static int build_audio_procunit(struct mixer_build *state, int unitid,
 			break;
 		}
 
+		err = get_cur_ctl_value(cval, cval->control << 8, &val);
+		if (err < 0) {
+			usb_mixer_elem_info_free(cval);
+			return -EINVAL;
+		}
+
 		kctl = snd_ctl_new1(&mixer_procunit_ctl, cval);
 		if (!kctl) {
 			usb_mixer_elem_info_free(cval);
-- 
2.25.1