[PATCH v3 0/2] ALSA: usb-audio: Add QUIRK_FLAG_MIXER_GET_CUR_BROKEN for Sennheiser MOMENTUM 3

[PATCH v3 0/2] ALSA: usb-audio: Add QUIRK_FLAG_MIXER_GET_CUR_BROKEN for Sennheiser MOMENTUM 3

[Rong Zhang]

Since commit 86aa1ea1f15c ("ALSA: usb-audio: Do not expose sticky
mixers"), the UAC mixer core utilizes volume SET_CUR and GET_CUR to
identify devices with sticky mixers. Unfortunately, even though most
devices with sticky GET_CUR also have corresponding sticky SET_CUR,
which I actually met more since the commit had been merged, there is
also a rare case that some devices may have volume mixers that responds
to SET_CUR properly but with its GET_CUR stubbed. This cause the sticky
check to consider the mixer to be sticky and unnecessarily disable it.

As the sticky check can't distinguish between sticky mixers and working
SET_CUR but broken GET_CUR, add QUIRK_FLAG_MIXER_GET_CUR_BROKEN to tell
that the device should fall into the second category when GET_CUR
returns a constant value. In this case, the sticky check becomes
non-fatal and only disables GET_CUR instead of the whole mixer. The
current volume will then be provided by the internal cache that stores
the last set volume.

The Sennheiser MOMENTUM 3 needs the quirk flag. Though its UAC mixer
works fine and precisely corresponds to the reported dB range, the
mixer's volume GET_CUR method is somehow stubbed and returns a constant
value (15dB), resulting in it being disabled by the sticky check.

Signed-off-by: Rong Zhang <i@rong.moe>
---
Changes in v3:
- Make the log less noisy (thanks Takashi Iwai)
- Do not propagate mixer values written by sanity checks when GET_CUR is
  broken, nor restore the garbage backed-up value. Instead, rely on
  init_cur_mix_raw() to initialize the mixer properly
- Gate cache invalidation as well, so that the current volume is always
  available to userspace
- Update the comment of check_sticky_volume_control()
- Link to v2: https://patch.msgid.link/20260528-uac-quirk-get-cur-vol-v2-0-84d3c8f48150@rong.moe

Changes in v2:
- Turn the approach into a less radical one
  - Rename the quirk flag to QUIRK_FLAG_MIXER_GET_CUR_BROKEN
  - Add a flag `get_cur_broken' to `struct usb_mixer_elem_info'
  - When the sticky check fails, check quirk flags. Gate further GET_CUR
    by setting `cval->get_cur_broken' if QUIRK_FLAG_MIXER_GET_CUR_BROKEN
    is set, otherwise disable the mixer as usual
  - The quirk flag still applies to all mixers, but as long as a mixer
    makes the sticky check happy, it won't be affected at all. Only
    those mixers with constant GET_CUR values will have their GET_CUR
    gated. I assume the impact is minimal, since it's very unlikely a
    device would have sticky mixers (broken SET_CUR) along with mixers
    with working SET_CUR but broken GET_CUR at the same time
- Link to v1: https://patch.msgid.link/20260527-uac-quirk-get-cur-vol-v1-0-e9362b712e5e@rong.moe

---
Rong Zhang (2):
      ALSA: usb-audio: Add QUIRK_FLAG_MIXER_GET_CUR_BROKEN
      ALSA: usb-audio: Add quirk flag for Sennheiser MOMENTUM 3

 Documentation/sound/alsa-configuration.rst | 12 +++++++
 sound/usb/mixer.c                          | 58 ++++++++++++++++++++++++------
 sound/usb/mixer.h                          |  1 +
 sound/usb/quirks.c                         |  3 ++
 sound/usb/usbaudio.h                       | 13 +++++++
 5 files changed, 77 insertions(+), 10 deletions(-)
---
base-commit: 17065203e1bc7e7f2786998d532cd93a06265156
change-id: 20260527-uac-quirk-get-cur-vol-d0b292c3e796

Thanks,
Rong

[PATCH v3 1/2] ALSA: usb-audio: Add QUIRK_FLAG_MIXER_GET_CUR_BROKEN

[Rong Zhang]

Since commit 86aa1ea1f15c ("ALSA: usb-audio: Do not expose sticky
mixers"), the UAC mixer core utilizes volume SET_CUR and GET_CUR to
identify devices with sticky mixers. Unfortunately, even though most
devices with sticky GET_CUR also have corresponding sticky SET_CUR,
which I actually met more since the commit had been merged, there is
also a rare case that some devices may have volume mixers that responds
to SET_CUR properly but with its GET_CUR stubbed. This cause the sticky
check to consider the mixer to be sticky and unnecessarily disable it.

As the sticky check can't distinguish between sticky mixers and working
SET_CUR but broken GET_CUR, add QUIRK_FLAG_MIXER_GET_CUR_BROKEN to tell
that the device should fall into the second category when GET_CUR
returns a constant value. In this case, the sticky check becomes
non-fatal and only disables GET_CUR instead of the whole mixer. The
current volume will then be provided by the internal cache that stores
the last set volume.

Signed-off-by: Rong Zhang <i@rong.moe>
---
 Documentation/sound/alsa-configuration.rst | 12 +++++++
 sound/usb/mixer.c                          | 58 ++++++++++++++++++++++++------
 sound/usb/mixer.h                          |  1 +
 sound/usb/quirks.c                         |  1 +
 sound/usb/usbaudio.h                       | 13 +++++++
 5 files changed, 75 insertions(+), 10 deletions(-)

diff --git a/Documentation/sound/alsa-configuration.rst b/Documentation/sound/alsa-configuration.rst
index 4b30cd63c5a5..78fb484e8b04 100644
--- a/Documentation/sound/alsa-configuration.rst
+++ b/Documentation/sound/alsa-configuration.rst
@@ -2389,6 +2389,18 @@ quirk_flags
           from snd_usb_handle_sync_urb. Instead fall through and enqueue a
           packet_info containing only size-0 packets, so the OUT ring keeps
           moving (emits silence). Needed by Behringer Flow 8 (1397:050c).
+        * bit 30: ``mixer_get_cur_broken``
+          Some mixers are sticky, which means that setting their current volume
+          is a no-op, and reading the current volume returns a constant value.
+          The sticky check disables these mixers to prevent confusing userspace.
+          However, some devices do have a tunable volume despite the reported
+          current volume being constant. As the sticky check can't distinguish
+          between the two categories, setting this flag tells that the device
+          should fall into the second category when GET_CUR returns a constant
+          value, resulting in the sticky check being non-fatal and only
+          disabling GET_CUR instead of the whole mixer. The current volume will
+          then be provided by the internal cache that stores the last set
+          volume
 
 This module supports multiple devices, autoprobe and hotplugging.
 
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index d61bde654219..b98222e5f697 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -434,6 +434,11 @@ int snd_usb_get_cur_mix_value(struct usb_mixer_elem_info *cval,
 		*value = cval->cache_val[index];
 		return 0;
 	}
+
+	/* The current value is always provided by the cache after initialization. */
+	if (cval->get_cur_broken)
+		return -ENXIO;
+
 	err = get_cur_mix_raw(cval, channel, value);
 	if (err < 0) {
 		if (!cval->head.mixer->ignore_ctl_error)
@@ -1223,7 +1228,7 @@ static void init_cur_mix_raw(struct usb_mixer_elem_info *cval, int ch, int idx)
 	err = snd_usb_get_cur_mix_value(cval, ch, idx, &val);
 	if (!err)
 		return;
-	if (!cval->head.mixer->ignore_ctl_error)
+	if (!cval->head.mixer->ignore_ctl_error && !cval->get_cur_broken)
 		usb_audio_warn(cval->head.mixer->chip,
 			       "%d:%d: failed to get current value for ch %d (%d)\n",
 			       cval->head.id, mixer_ctrl_intf(cval->head.mixer),
@@ -1237,8 +1242,16 @@ static void init_cur_mix_raw(struct usb_mixer_elem_info *cval, int ch, int idx)
  * Some devices' volume control mixers are sticky, which accept SET_CUR but
  * do absolutely nothing.
  *
- * Prevent sticky mixers from being registered, otherwise they confuses
- * userspace and results in ineffective volume control.
+ * Check the return values of GET_CUR with different SET_CUR values. Consider
+ * the mixer as sticky if GET_CUR always returns a constant value.
+ *
+ * Some devices have effective SET_CUR despite GET_CUR being constant. Do not
+ * consider the mixer as sticky if a quirk flag indicates that.
+ *
+ * Gate the registration of sticky mixers to prevent confusing userspace, so
+ * that they won't cause ineffective volume control. However, for mixers with
+ * effective SET_CUR but broken GET_CUR, the registration can continue normally
+ * but further GET_CUR requests will be gated.
  */
 static int check_sticky_volume_control(struct usb_mixer_elem_info *cval,
 				       int channel, int saved)
@@ -1258,6 +1271,16 @@ static int check_sticky_volume_control(struct usb_mixer_elem_info *cval,
 			return 0;
 	}
 
+	if (cval->head.mixer->chip->quirk_flags & QUIRK_FLAG_MIXER_GET_CUR_BROKEN) {
+		usb_audio_info(cval->head.mixer->chip,
+			       "%d:%d: broken mixer GET_CUR (%d/%d/%d => %d)\n",
+			       cval->head.id, mixer_ctrl_intf(cval->head.mixer),
+			       cval->min, cval->max, cval->res, saved);
+
+		cval->get_cur_broken = 1;
+		return -ENXIO;
+	}
+
 	usb_audio_err(cval->head.mixer->chip,
 		      "%d:%d: sticky mixer values (%d/%d/%d => %d), disabling\n",
 		      cval->head.id, mixer_ctrl_intf(cval->head.mixer),
@@ -1304,7 +1327,7 @@ static void check_volume_control_res(struct usb_mixer_elem_info *cval,
 static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval,
 				   int default_min, struct snd_kcontrol *kctl)
 {
-	int i, idx, ret;
+	int i, idx, ret = 0;
 
 	/* for failsafe */
 	cval->min = default_min;
@@ -1360,10 +1383,12 @@ static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval,
 				goto no_checks;
 
 			ret = check_sticky_volume_control(cval, minchn, saved);
-			if (ret < 0) {
+			if (ret == -ENODEV) {
 				snd_usb_set_cur_mix_value(cval, minchn, 0, saved);
 				return ret;
 			}
+			if (ret)
+				goto no_checks;
 
 			if (cval->min + cval->res < cval->max)
 				check_volume_control_res(cval, minchn, saved);
@@ -1372,6 +1397,16 @@ static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval,
 		}
 
 no_checks:
+		/*
+		 * Got a non-fatal failure during sanity checks.
+		 *
+		 * Do not propagate mixer values written by sanity checks.
+		 * Instead, rely on init_cur_mix_raw() to initialize the mixer
+		 * properly.
+		 */
+		if (ret)
+			cval->cached = 0;
+
 		cval->initialized = 1;
 	}
 
@@ -3513,7 +3548,8 @@ void snd_usb_mixer_notify_id(struct usb_mixer_interface *mixer, int unitid)
 			continue;
 		info = mixer_elem_list_to_info(list);
 		/* invalidate cache, so the value is read from the device */
-		info->cached = 0;
+		if (!info->get_cur_broken)
+			info->cached = 0;
 		snd_ctl_notify(mixer->chip->card, SNDRV_CTL_EVENT_MASK_VALUE,
 			       &list->kctl->id);
 	}
@@ -3610,10 +3646,12 @@ static void snd_usb_mixer_interrupt_v2(struct usb_mixer_interface *mixer,
 		switch (attribute) {
 		case UAC2_CS_CUR:
 			/* invalidate cache, so the value is read from the device */
-			if (channel)
-				info->cached &= ~BIT(channel);
-			else /* master channel */
-				info->cached = 0;
+			if (!info->get_cur_broken) {
+				if (channel)
+					info->cached &= ~BIT(channel);
+				else /* master channel */
+					info->cached = 0;
+			}
 
 			snd_ctl_notify(mixer->chip->card, SNDRV_CTL_EVENT_MASK_VALUE,
 				       &info->head.kctl->id);
diff --git a/sound/usb/mixer.h b/sound/usb/mixer.h
index afbb3dd9f177..3fa1bd96f858 100644
--- a/sound/usb/mixer.h
+++ b/sound/usb/mixer.h
@@ -94,6 +94,7 @@ struct usb_mixer_elem_info {
 	int cache_val[MAX_CHANNELS];
 	u8 initialized;
 	u8 min_mute;
+	u8 get_cur_broken;
 	void *private_data;
 };
 
diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index e2c95be38aca..ac2f0f6039be 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -2605,6 +2605,7 @@ static const char *const snd_usb_audio_quirk_flag_names[] = {
 	QUIRK_STRING_ENTRY(MIXER_PLAYBACK_LINEAR_VOL),
 	QUIRK_STRING_ENTRY(MIXER_CAPTURE_LINEAR_VOL),
 	QUIRK_STRING_ENTRY(IFB_SILENCE_ON_EMPTY),
+	QUIRK_STRING_ENTRY(MIXER_GET_CUR_BROKEN),
 	NULL
 };
 
diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h
index 9afcad8f143a..e472aef6eb87 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -242,6 +242,17 @@ extern bool snd_usb_skip_validation;
  *  from snd_usb_handle_sync_urb. Instead fall through and enqueue a
  *  packet_info containing only size-0 packets, so the OUT ring keeps
  *  moving (emits silence). Needed by Behringer Flow 8 (1397:050c).
+ * QUIRK_FLAG_MIXER_GET_CUR_BROKEN
+ *  Some mixers are sticky, which means that setting their current volume is a
+ *  no-op, and reading the current volume returns a constant value. The sticky
+ *  check disables these mixers to prevent confusing userspace. However, some
+ *  devices do have a tunable volume despite the reported current volume being
+ *  constant. As the sticky check can't distinguish between the two categories,
+ *  setting this flag tells that the device should fall into the second
+ *  category when GET_CUR returns a constant value, resulting in the sticky
+ *  check being non-fatal and only disabling GET_CUR instead of the whole mixer.
+ *  The current volume will then be provided by the internal cache that stores
+ *  the last set volume
  */
 
 enum {
@@ -275,6 +286,7 @@ enum {
 	QUIRK_TYPE_MIXER_PLAYBACK_LINEAR_VOL	= 27,
 	QUIRK_TYPE_MIXER_CAPTURE_LINEAR_VOL	= 28,
 	QUIRK_TYPE_IFB_SILENCE_ON_EMPTY		= 29,
+	QUIRK_TYPE_MIXER_GET_CUR_BROKEN		= 30,
 /* Please also edit snd_usb_audio_quirk_flag_names */
 };
 
@@ -310,5 +322,6 @@ enum {
 #define QUIRK_FLAG_MIXER_PLAYBACK_LINEAR_VOL	QUIRK_FLAG(MIXER_PLAYBACK_LINEAR_VOL)
 #define QUIRK_FLAG_MIXER_CAPTURE_LINEAR_VOL	QUIRK_FLAG(MIXER_CAPTURE_LINEAR_VOL)
 #define QUIRK_FLAG_IFB_SILENCE_ON_EMPTY		QUIRK_FLAG(IFB_SILENCE_ON_EMPTY)
+#define QUIRK_FLAG_MIXER_GET_CUR_BROKEN		QUIRK_FLAG(MIXER_GET_CUR_BROKEN)
 
 #endif /* __USBAUDIO_H */

-- 
2.53.0

[PATCH v3 2/2] ALSA: usb-audio: Add quirk flag for Sennheiser MOMENTUM 3

[Rong Zhang]

The Sennheiser MOMENTUM 3 is a wireless around-ear headphones featuring
ANC, which can be connected via Bluetooth or USB-C.

When connecting via USB-C, its UAC mixer works fine and precisely
corresponds to the reported dB range. However, the mixer's volume
GET_CUR method is somehow stubbed and returns a constant value (15dB).
Since commit 86aa1ea1f15c ("ALSA: usb-audio: Do not expose sticky
mixers"), the sticky check considers the mixer to be sticky and
unnecessarily disables the mixer.

Add a quirk table entry matching VID/PID=0x1377/0x6004 and applying
the MIXER_GET_CUR_BROKEN quirk flag, so that the mixer is usable again.

Quirky device sample:

  usb 7-1.4.4.1.1.1: new full-speed USB device number 30 using xhci_hcd
  usb 7-1.4.4.1.1.1: New USB device found, idVendor=1377, idProduct=6004, bcdDevice=38.85
  usb 7-1.4.4.1.1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
  usb 7-1.4.4.1.1.1: Product: MOMENTUM 3
  usb 7-1.4.4.1.1.1: Manufacturer: Sennheiser electronic GmbH & Co. KG
  usb 7-1.4.4.1.1.1: SerialNumber: <REDACTED>
  usb 7-1.4.4.1.1.1: Found last interface = 0
  usb 7-1.4.4.1.1.1: 1:1: add audio endpoint 0x3
  usb 7-1.4.4.1.1.1: Creating new data endpoint #3
  usb 7-1.4.4.1.1.1: 1:1 Set sample rate 48000, clock 0
  usb 7-1.4.4.1.1.1: 6:0: sticky mixer values (0/11520/768 => 3840), disabling
  usb 7-1.4.4.1.1.1: [6] FU [PCM Playback Volume] skipped due to invalid volume
  input: Sennheiser electronic GmbH & Co. KG MOMENTUM 3 as /devices/pci0000:00/0000:00:08.3/0000:67:00.4/usb7/7-1/7-1.4/7-1.4.4/7-1.4.4.1/7-1.4.4.1.1/7-1.4.4.1.1.1/7-1.4.4.1.1.1:1.2/0003:1377:6004.002B/input/input208
  input: Sennheiser electronic GmbH & Co. KG MOMENTUM 3 Consumer Control as /devices/pci0000:00/0000:00:08.3/0000:67:00.4/usb7/7-1/7-1.4/7-1.4.4/7-1.4.4.1/7-1.4.4.1.1/7-1.4.4.1.1.1/7-1.4.4.1.1.1:1.2/0003:1377:6004.002B/input/input209
  hid-generic 0003:1377:6004.002B: input,hiddev99,hidraw12: USB HID v1.11 Device [Sennheiser electronic GmbH & Co. KG MOMENTUM 3] on usb-0000:67:00.4-1.4.4.1.1.1/input2

Signed-off-by: Rong Zhang <i@rong.moe>
---
 sound/usb/quirks.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index ac2f0f6039be..149f2009df12 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -2357,6 +2357,8 @@ static const struct usb_audio_quirk_flags_table quirk_flags_table[] = {
 		   QUIRK_FLAG_FORCE_IFACE_RESET | QUIRK_FLAG_IFACE_DELAY),
 	DEVICE_FLG(0x1224, 0x2a25, /* Jieli Technology USB PHY 2.0 */
 		   QUIRK_FLAG_GET_SAMPLE_RATE | QUIRK_FLAG_MIC_RES_16),
+	DEVICE_FLG(0x1377, 0x6004, /* Sennheiser MOMENTUM 3 */
+		   QUIRK_FLAG_MIXER_GET_CUR_BROKEN),
 	DEVICE_FLG(0x1395, 0x740a, /* Sennheiser DECT */
 		   QUIRK_FLAG_GET_SAMPLE_RATE),
 	DEVICE_FLG(0x1397, 0x0507, /* Behringer UMC202HD */

-- 
2.53.0

Re: [PATCH v3 0/2] ALSA: usb-audio: Add QUIRK_FLAG_MIXER_GET_CUR_BROKEN for Sennheiser MOMENTUM 3

[Takashi Iwai]

On Thu, 28 May 2026 20:38:54 +0200,
Rong Zhang wrote:
> 
> Since commit 86aa1ea1f15c ("ALSA: usb-audio: Do not expose sticky
> mixers"), the UAC mixer core utilizes volume SET_CUR and GET_CUR to
> identify devices with sticky mixers. Unfortunately, even though most
> devices with sticky GET_CUR also have corresponding sticky SET_CUR,
> which I actually met more since the commit had been merged, there is
> also a rare case that some devices may have volume mixers that responds
> to SET_CUR properly but with its GET_CUR stubbed. This cause the sticky
> check to consider the mixer to be sticky and unnecessarily disable it.
> 
> As the sticky check can't distinguish between sticky mixers and working
> SET_CUR but broken GET_CUR, add QUIRK_FLAG_MIXER_GET_CUR_BROKEN to tell
> that the device should fall into the second category when GET_CUR
> returns a constant value. In this case, the sticky check becomes
> non-fatal and only disables GET_CUR instead of the whole mixer. The
> current volume will then be provided by the internal cache that stores
> the last set volume.
> 
> The Sennheiser MOMENTUM 3 needs the quirk flag. Though its UAC mixer
> works fine and precisely corresponds to the reported dB range, the
> mixer's volume GET_CUR method is somehow stubbed and returns a constant
> value (15dB), resulting in it being disabled by the sticky check.
> 
> Signed-off-by: Rong Zhang <i@rong.moe>

Applied to for-next branch now.  Thanks.


Takashi