[PATCH 0/4] usb-audio: fix mixer write failure handling

[PATCH 0/4] usb-audio: fix mixer write failure handling

[Cássio Gabriel]

This series fixes usb-audio mixer put() paths that currently report
success even when the underlying device write fails.

The issue exists in the generic mixer core callbacks, the Scarlett
Gen1 enum path, and several Tascam US-16x08 put() callbacks.

The US-16x08 EQ and compressor callbacks have an additional bug: they
update their software shadow state before sending the USB write, so a
failed transfer can leave later get() results out of sync with the
hardware state.

The series is split into four patches:
- propagate write failures in the generic mixer core callbacks
- fix the Scarlett Gen1 enum callback
- propagate write failures in the simple US-16x08 put() callbacks
- commit the US-16x08 EQ and compressor shadow state only after a
successful write

Successful writes are unchanged. Failed writes are now reported
correctly, and the US-16x08 shadow state remains coherent with the
hardware after write errors.

Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
---
Cássio Gabriel (4):
      ALSA: usb-audio: Propagate write errors in generic mixer put callbacks
      ALSA: usb-audio: Propagate errors in scarlett_ctl_enum_put()
      ALSA: usb-audio: Propagate US-16x08 write errors in route/mix EQ-switch put callbacks
      ALSA: usb-audio: Update US-16x08 EQ/comp shadow state after successful writes

 sound/usb/mixer.c          |  17 ++++--
 sound/usb/mixer_scarlett.c |   4 +-
 sound/usb/mixer_us16x08.c  | 127 +++++++++++++++++++++++++++------------------
 3 files changed, 92 insertions(+), 56 deletions(-)
---
base-commit: 99c71f13f9841f8c67fa7595bf0834d3045f5d24
change-id: 20260416-usb-write-error-propagation-20c69e2c5cab

Best regards,
--  
Cássio Gabriel <cassiogabrielcontato@gmail.com>

[PATCH 1/4] ALSA: usb-audio: Propagate write errors in generic mixer put callbacks

[Cássio Gabriel]

mixer_ctl_feature_put(), mixer_ctl_procunit_put(), and
mixer_ctl_selector_put() ignore failures from their SET_CUR helper
routines and report the control as changed whenever the requested
value differs from the current one.

If the device rejects the write, userspace still sees success although
the hardware state did not change. Propagate write failures instead,
using filter_error() so ignore_ctl_error keeps the same semantics as
the existing get paths.

Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
---
 sound/usb/mixer.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 85653112e7f3..9d9ed68166c8 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1526,7 +1526,10 @@ static int mixer_ctl_feature_put(struct snd_kcontrol *kcontrol,
 				return -EINVAL;
 			val = get_abs_value(cval, val);
 			if (oval != val) {
-				snd_usb_set_cur_mix_value(cval, c + 1, cnt, val);
+				err = snd_usb_set_cur_mix_value(cval, c + 1,
+								cnt, val);
+				if (err < 0)
+					return filter_error(cval, err);
 				changed = 1;
 			}
 			cnt++;
@@ -1541,7 +1544,9 @@ static int mixer_ctl_feature_put(struct snd_kcontrol *kcontrol,
 			return -EINVAL;
 		val = get_abs_value(cval, val);
 		if (val != oval) {
-			snd_usb_set_cur_mix_value(cval, 0, 0, val);
+			err = snd_usb_set_cur_mix_value(cval, 0, 0, val);
+			if (err < 0)
+				return filter_error(cval, err);
 			changed = 1;
 		}
 	}
@@ -2466,7 +2471,9 @@ static int mixer_ctl_procunit_put(struct snd_kcontrol *kcontrol,
 		return -EINVAL;
 	val = get_abs_value(cval, val);
 	if (val != oval) {
-		set_cur_ctl_value(cval, cval->control << 8, val);
+		err = set_cur_ctl_value(cval, cval->control << 8, val);
+		if (err < 0)
+			return filter_error(cval, err);
 		return 1;
 	}
 	return 0;
@@ -2832,7 +2839,9 @@ static int mixer_ctl_selector_put(struct snd_kcontrol *kcontrol,
 		return -EINVAL;
 	val = get_abs_value(cval, val);
 	if (val != oval) {
-		set_cur_ctl_value(cval, cval->control << 8, val);
+		err = set_cur_ctl_value(cval, cval->control << 8, val);
+		if (err < 0)
+			return filter_error(cval, err);
 		return 1;
 	}
 	return 0;

-- 
2.53.0

[PATCH 2/4] ALSA: usb-audio: Propagate errors in scarlett_ctl_enum_put()

[Cássio Gabriel]

scarlett_ctl_enum_put() ignores the return value from
snd_usb_set_cur_mix_value() and reports success whenever the
requested enum value differs from the current one.

If the SET_CUR request fails, the callback still returns success even
though neither the hardware state nor the cached mixer value changed.

Fixes: 76b188c4b370 ("ALSA: usb-audio: Scarlett mixer interface for 6i6, 18i6, 18i8 and 18i20")
Cc: stable@vger.kernel.org
Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
---
 sound/usb/mixer_scarlett.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sound/usb/mixer_scarlett.c b/sound/usb/mixer_scarlett.c
index 1bb01e827654..673eb8d8724d 100644
--- a/sound/usb/mixer_scarlett.c
+++ b/sound/usb/mixer_scarlett.c
@@ -680,7 +680,9 @@ static int scarlett_ctl_enum_put(struct snd_kcontrol *kctl,
 	val = ucontrol->value.integer.value[0];
 	val = val + opt->start;
 	if (val != oval) {
-		snd_usb_set_cur_mix_value(elem, 0, 0, val);
+		err = snd_usb_set_cur_mix_value(elem, 0, 0, val);
+		if (err < 0)
+			return err;
 		return 1;
 	}
 	return 0;

-- 
2.53.0

[PATCH 3/4] ALSA: usb-audio: Propagate US-16x08 write errors in route/mix EQ-switch put callbacks

[Cássio Gabriel]

Several US-16x08 mixer put callbacks log failed control URBs but
still return success to userspace. That hides device write failures
even though the requested value was not applied.

Return the negative write error instead in the route, master, bus,
channel, and EQ switch put callbacks.

Fixes: d2bb390a2081 ("ALSA: usb-audio: Tascam US-16x08 DSP mixer quirk")
Cc: stable@vger.kernel.org
Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
---
 sound/usb/mixer_us16x08.c | 49 +++++++++++++++++++++++------------------------
 1 file changed, 24 insertions(+), 25 deletions(-)

diff --git a/sound/usb/mixer_us16x08.c b/sound/usb/mixer_us16x08.c
index 8a02964e5d7b..fcf7dfa4aa84 100644
--- a/sound/usb/mixer_us16x08.c
+++ b/sound/usb/mixer_us16x08.c
@@ -224,14 +224,14 @@ static int snd_us16x08_route_put(struct snd_kcontrol *kcontrol,
 
 	err = snd_us16x08_send_urb(chip, buf, sizeof(route_msg));
 
-	if (err > 0) {
-		elem->cached |= 1 << index;
-		elem->cache_val[index] = val;
-	} else {
+	if (err < 0) {
 		usb_audio_dbg(chip, "Failed to set routing, err:%d\n", err);
+		return err;
 	}
 
-	return err > 0 ? 1 : 0;
+	elem->cached |= 1 << index;
+	elem->cache_val[index] = val;
+	return 1;
 }
 
 static int snd_us16x08_master_info(struct snd_kcontrol *kcontrol,
@@ -283,14 +283,14 @@ static int snd_us16x08_master_put(struct snd_kcontrol *kcontrol,
 	buf[5] = index + 1;
 	err = snd_us16x08_send_urb(chip, buf, sizeof(mix_msg_out));
 
-	if (err > 0) {
-		elem->cached |= 1 << index;
-		elem->cache_val[index] = val;
-	} else {
+	if (err < 0) {
 		usb_audio_dbg(chip, "Failed to set master, err:%d\n", err);
+		return err;
 	}
 
-	return err > 0 ? 1 : 0;
+	elem->cached |= 1 << index;
+	elem->cache_val[index] = val;
+	return 1;
 }
 
 static int snd_us16x08_bus_put(struct snd_kcontrol *kcontrol,
@@ -324,14 +324,14 @@ static int snd_us16x08_bus_put(struct snd_kcontrol *kcontrol,
 		break;
 	}
 
-	if (err > 0) {
-		elem->cached |= 1;
-		elem->cache_val[0] = val;
-	} else {
+	if (err < 0) {
 		usb_audio_dbg(chip, "Failed to set bus parameter, err:%d\n", err);
+		return err;
 	}
 
-	return err > 0 ? 1 : 0;
+	elem->cached |= 1;
+	elem->cache_val[0] = val;
+	return 1;
 }
 
 static int snd_us16x08_bus_get(struct snd_kcontrol *kcontrol,
@@ -392,14 +392,14 @@ static int snd_us16x08_channel_put(struct snd_kcontrol *kcontrol,
 
 	err = snd_us16x08_send_urb(chip, buf, sizeof(mix_msg_in));
 
-	if (err > 0) {
-		elem->cached |= 1 << index;
-		elem->cache_val[index] = val;
-	} else {
+	if (err < 0) {
 		usb_audio_dbg(chip, "Failed to set channel, err:%d\n", err);
+		return err;
 	}
 
-	return err > 0 ? 1 : 0;
+	elem->cached |= 1 << index;
+	elem->cache_val[index] = val;
+	return 1;
 }
 
 static int snd_us16x08_mix_info(struct snd_kcontrol *kcontrol,
@@ -529,13 +529,13 @@ static int snd_us16x08_eqswitch_put(struct snd_kcontrol *kcontrol,
 		msleep(15);
 	}
 
-	if (err > 0) {
-		elem->cached |= 1 << index;
-		elem->cache_val[index] = val;
-	} else {
+	if (err < 0) {
 		usb_audio_dbg(chip, "Failed to set eq switch, err:%d\n", err);
+		return err;
 	}
 
+	elem->cached |= 1 << index;
+	elem->cache_val[index] = val;
 	return 1;
 }
 
@@ -1418,4 +1418,3 @@ int snd_us16x08_controls_create(struct usb_mixer_interface *mixer)
 
 	return 0;
 }
-

-- 
2.53.0

[PATCH 4/4] ALSA: usb-audio: Update US-16x08 EQ/comp shadow state after successful writes

[Cássio Gabriel]

snd_us16x08_comp_put() and snd_us16x08_eq_put() update their
software stores before sending the USB write. If the transfer
fails, later get callbacks report a value the hardware never
accepted.

Build the outgoing message from the current store plus the
pending value, then commit the store only after a successful
write.

Fixes: d2bb390a2081 ("ALSA: usb-audio: Tascam US-16x08 DSP mixer quirk")
Cc: stable@vger.kernel.org
Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
---
 sound/usb/mixer_us16x08.c | 78 +++++++++++++++++++++++++++++++----------------
 1 file changed, 52 insertions(+), 26 deletions(-)

diff --git a/sound/usb/mixer_us16x08.c b/sound/usb/mixer_us16x08.c
index fcf7dfa4aa84..ebff185cbd2c 100644
--- a/sound/usb/mixer_us16x08.c
+++ b/sound/usb/mixer_us16x08.c
@@ -435,6 +435,7 @@ static int snd_us16x08_comp_put(struct snd_kcontrol *kcontrol,
 	int index = ucontrol->id.index;
 	char buf[sizeof(comp_msg)];
 	int val_idx, val;
+	int threshold, ratio, attack, release, gain, switch_on;
 	int err;
 
 	val = ucontrol->value.integer.value[0];
@@ -447,36 +448,61 @@ static int snd_us16x08_comp_put(struct snd_kcontrol *kcontrol,
 	/* new control value incl. bias*/
 	val_idx = elem->head.id - SND_US16X08_ID_COMP_BASE;
 
-	store->val[val_idx][index] = ucontrol->value.integer.value[0];
+	threshold = store->val[COMP_STORE_IDX(SND_US16X08_ID_COMP_THRESHOLD)]
+		[index];
+	ratio = store->val[COMP_STORE_IDX(SND_US16X08_ID_COMP_RATIO)][index];
+	attack = store->val[COMP_STORE_IDX(SND_US16X08_ID_COMP_ATTACK)][index];
+	release = store->val[COMP_STORE_IDX(SND_US16X08_ID_COMP_RELEASE)]
+		[index];
+	gain = store->val[COMP_STORE_IDX(SND_US16X08_ID_COMP_GAIN)][index];
+	switch_on = store->val[COMP_STORE_IDX(SND_US16X08_ID_COMP_SWITCH)]
+		[index];
+
+	switch (val_idx) {
+	case COMP_STORE_IDX(SND_US16X08_ID_COMP_THRESHOLD):
+		threshold = val;
+		break;
+	case COMP_STORE_IDX(SND_US16X08_ID_COMP_RATIO):
+		ratio = val;
+		break;
+	case COMP_STORE_IDX(SND_US16X08_ID_COMP_ATTACK):
+		attack = val;
+		break;
+	case COMP_STORE_IDX(SND_US16X08_ID_COMP_RELEASE):
+		release = val;
+		break;
+	case COMP_STORE_IDX(SND_US16X08_ID_COMP_GAIN):
+		gain = val;
+		break;
+	case COMP_STORE_IDX(SND_US16X08_ID_COMP_SWITCH):
+		switch_on = val;
+		break;
+	}
 
 	/* prepare compressor URB message from template  */
 	memcpy(buf, comp_msg, sizeof(comp_msg));
 
 	/* place comp values in message buffer watch bias! */
-	buf[8] = store->val[
-		COMP_STORE_IDX(SND_US16X08_ID_COMP_THRESHOLD)][index]
-		- SND_US16X08_COMP_THRESHOLD_BIAS;
-	buf[11] = ratio_map[store->val[
-		COMP_STORE_IDX(SND_US16X08_ID_COMP_RATIO)][index]];
-	buf[14] = store->val[COMP_STORE_IDX(SND_US16X08_ID_COMP_ATTACK)][index]
-		+ SND_US16X08_COMP_ATTACK_BIAS;
-	buf[17] = store->val[COMP_STORE_IDX(SND_US16X08_ID_COMP_RELEASE)][index]
-		+ SND_US16X08_COMP_RELEASE_BIAS;
-	buf[20] = store->val[COMP_STORE_IDX(SND_US16X08_ID_COMP_GAIN)][index];
-	buf[26] = store->val[COMP_STORE_IDX(SND_US16X08_ID_COMP_SWITCH)][index];
+	buf[8] = threshold - SND_US16X08_COMP_THRESHOLD_BIAS;
+	buf[11] = ratio_map[ratio];
+	buf[14] = attack + SND_US16X08_COMP_ATTACK_BIAS;
+	buf[17] = release + SND_US16X08_COMP_RELEASE_BIAS;
+	buf[20] = gain;
+	buf[26] = switch_on;
 
 	/* place channel selector in message buffer */
 	buf[5] = index + 1;
 
 	err = snd_us16x08_send_urb(chip, buf, sizeof(comp_msg));
 
-	if (err > 0) {
-		elem->cached |= 1 << index;
-		elem->cache_val[index] = val;
-	} else {
+	if (err < 0) {
 		usb_audio_dbg(chip, "Failed to set compressor, err:%d\n", err);
+		return err;
 	}
 
+	store->val[val_idx][index] = val;
+	elem->cached |= 1 << index;
+	elem->cache_val[index] = val;
 	return 1;
 }
 
@@ -578,11 +604,10 @@ static int snd_us16x08_eq_put(struct snd_kcontrol *kcontrol,
 	/* copy URB buffer from EQ template */
 	memcpy(buf, eqs_msq, sizeof(eqs_msq));
 
-	store->val[b_idx][p_idx][index] = val;
-	buf[20] = store->val[b_idx][3][index];
-	buf[17] = store->val[b_idx][2][index];
-	buf[14] = store->val[b_idx][1][index];
-	buf[11] = store->val[b_idx][0][index];
+	buf[20] = p_idx == 3 ? val : store->val[b_idx][3][index];
+	buf[17] = p_idx == 2 ? val : store->val[b_idx][2][index];
+	buf[14] = p_idx == 1 ? val : store->val[b_idx][1][index];
+	buf[11] = p_idx == 0 ? val : store->val[b_idx][0][index];
 
 	/* place channel index in URB buffer */
 	buf[5] = index + 1;
@@ -592,14 +617,15 @@ static int snd_us16x08_eq_put(struct snd_kcontrol *kcontrol,
 
 	err = snd_us16x08_send_urb(chip, buf, sizeof(eqs_msq));
 
-	if (err > 0) {
-		/* store new value in EQ band cache */
-		elem->cached |= 1 << index;
-		elem->cache_val[index] = val;
-	} else {
+	if (err < 0) {
 		usb_audio_dbg(chip, "Failed to set eq param, err:%d\n", err);
+		return err;
 	}
 
+	store->val[b_idx][p_idx][index] = val;
+	/* store new value in EQ band cache */
+	elem->cached |= 1 << index;
+	elem->cache_val[index] = val;
 	return 1;
 }
 

-- 
2.53.0