Re: [PATCH] ALSA: usb-audio: Check sticky mixers precisely

[Alexander Niemeyer <adventureFAN@gmx.de>]

Hi Rong,

thanks. I have now completed the three tests you asked for.

1. Your sticky-check patch with the detachable Mic boom attached

I tested the same minimal 7.1.8 backport of your ~16-value / 10 ms
sticky-check logic again, this time with the detachable microphone boom
physically attached.

The external snd-usb-audio module was rebuilt and loaded successfully
(the module taint was "O"), and the old 100 ms diagnostic changes were
removed before this test.

The result is still a failure:

   sticky mixer values (-16384/0/256 => -3840), disabling

The PCM control exposes only:

   Capabilities: pswitch pswitch-joined

and no Playback Volume control.

I repeated this once more with another dongle replug, without changing
the module or touching the volume wheel, and got the same result again.

So:

   your sticky-check patch + Mic boom attached
   -> still classified as sticky
   -> reproduced twice


2. Is Playback SET_CUR really broken after Mic SET_RES with the boom 
detached?

For this test I detached the microphone boom.

I used a test version of snd-usb-audio which:

- performed the Mic UAC1 resolution probe,
- kept the Playback Volume control exposed,
- clamped the known-broken advertised -64 dB minimum to -63 dB,
- and bypassed the normal ALSA mixer cache so that mixer reads fetch
   GET_CUR from the device.

The initial Playback value was:

   43 = -20 dB

I played a 3-second 1 kHz test tone and listened to its level.

Then I requested:

   23 = -40 dB

The immediate output from the cset operation still showed:

   values=43

I waited two seconds and issued a fresh cget. It then returned:

   values=23

I played the exact same test tone again, and the second tone was clearly
quieter.

So Playback SET_CUR is physically effective.

At least in this test, the effect after Mic SET_RES with the boom
detached is not that Playback SET_CUR stops working. Instead, GET_CUR
can remain stale for some time after SET_CUR and later reflect the
actual value.

In short:

   before:             43 (-20 dB)
   SET_CUR requested:  23 (-40 dB)
   immediate result:   43
   GET_CUR after 2 s:  23
   physical volume:    clearly quieter


3. QUIRK_FLAG_MIXER_GET_CUR_BROKEN and mixer change notifications

Linux 7.1.8 does not contain QUIRK_FLAG_MIXER_GET_CUR_BROKEN yet, so for
this test I made a minimal backport of the flag behavior to the otherwise
stock 7.1.8 mixer code, without your new sticky-check patch.

I loaded snd-usb-audio with:

   quirk_flags=046d:0aba:mixer_get_cur_broken

The kernel detected the constant GET_CUR condition and kept the Playback
Volume control exposed:

   sticky mixer values (-16384/0/256 => -3840), disabling
   PROXTESTC: treating constant GET_CUR as broken

For this test the microphone boom was attached.

Before turning the physical headset wheel:

   ALSA cget: 56
   wpctl:     Volume 0.72

I then deliberately turned the physical volume wheel further down.

Afterwards:

   ALSA cget: 47
   wpctl:     Volume 0.52

KDE's volume OSD also reacted normally while I turned the wheel.

So, on this device, using MIXER_GET_CUR_BROKEN did not break propagation
of physical mixer changes through the audio stack:

   physical wheel
   -> ALSA value changed
   -> PipeWire value changed
   -> KDE OSD reacted normally


Therefore the current picture seems to be:

- Your revised sticky check still rejects the Playback Volume control,
   both with the detachable Mic boom attached and detached.

- With the Mic boom detached, Mic SET_RES can make Playback GET_CUR stay
   stale after a Playback SET_CUR, but Playback SET_CUR itself is still
   physically effective.

- At least on this Logitech device, treating GET_CUR as broken did not
   prevent physical wheel changes from reaching ALSA/PipeWire/KDE.

Let me know what you would like me to test next. I have kept the Fedora
test environment and module-signing setup intact.

Thanks,
Alexander

Am 19.08.2026 um 18:39 schrieb Rong Zhang:
> Hi Alexander,
>
> On Tue, 2026-08-18 at 17:24 +0200, Alexander Niemeyer wrote:
>> Hi Rong,
>>
>> one important follow-up to my previous message:
>>
>> I realized that the detachable microphone boom was not physically connected
>> to the headset during the direct libusb tests I reported earlier.
>>
>> I therefore repeated the relevant tests with the boom microphone attached,
>> and the result changes in an important way.
>>
>> With the boom microphone attached, on a fresh device:
>>
>> Mic GET_RES = 256
>> no SET_RES
>>
>> Playback:
>>     GET_CUR = -3840 (-15 dB)
>>     SET_CUR = -2048 (-8 dB)
>>     GET_CUR changes to -2048 after 65.3 ms
>>
>> Result: PASS
>>
>> After another power cycle, with the boom still attached:
>>
>> Mic GET_RES before = 256
>> Mic SET_RES(128)    = success
>> Mic GET_RES after  = 256
>>
>> Playback:
>>     GET_CUR = -3840 (-15 dB)
>>     SET_CUR = -2048 (-8 dB)
>>     GET_CUR changes to -2048 after 66.3 ms
>>
>> Result: PASS
>>
>> I also repeated the complete Mic SET_RES sequence:
>>
>> SET_RES 128
>> SET_RES 64
>> SET_RES 32
>> SET_RES 16
>> SET_RES 8
>> SET_RES 4
>> SET_RES 2
>> SET_RES 1
>>
>> All requests return success, GET_RES remains 256, and Playback
>> SET_CUR(-8 dB)
>> still works afterwards, with GET_CUR changing after 76.0 ms.
>>
>> However, with the boom microphone attached, the stock Fedora 7.1.8
>> snd-usb-audio driver still reproduces the original failure:
>>
>>     sticky mixer values (-16384/0/256 => -3840), disabling
>>
>> and no PCM Playback Volume control is exposed.
> Could you test my patch with Mic attached?
>
>> So I need to correct the conclusion from my previous message:
>>
>> The Mic SET_RES behavior is real, but it depends on whether the detachable
>> microphone boom is physically connected.
>>
>> With the boom disconnected:
>>     a single Mic SET_RES(128) is sufficient to make subsequent Playback
>>     SET_CUR ineffective for more than 1200 ms.
>>
>> With the boom connected:
>>     both a single Mic SET_RES(128) and the full SET_RES sequence leave
>>     Playback SET_CUR working normally.
>>
> Thanks for your tests.
>
> Let me conclude:
>
> - Mic detached: SET_RES on Mic breaks Playback
> - Mic attached: SET_RES on Mic breaks nothing
>
> Still, I doubt if Playback SET_CUR is really broken in the first case.
> There is a chance that Playback SET_CUR is effective while GET_CUR
> becomes broken.
>
> Could you test:
>
> - Leave the Mic detached
> - SET_RES on Mic
> - GET_CUR on Playback
> - Play some audio, listen to it
> - SET_CUR on Playback
> - GET_CUR on Playback
> - Play some audio again, listen to it, and tell if the physical volume
> has changed
>
> The procedure can be achieved by hacking into the snd-usb-audio driver
> and nullifying its cache mechanism, so that you can fetch GET_CUR values
> from standard ALSA mixer interface.
>
> If you can notice physical volume changes, it implies SET_RES on Mic
> break Playback GET_CUR without breaking SET_CUR. Otherwise, it break
> Playback SET_CUR.
>
> If it only breaks GET_CUR, it implies the methodology of sticky check is
> problematic. In this case I would probably consider demoting the sticky
> check's severity.
>
> I am also thinking about how we should demote the severity. Could you
> also test if applying QUIRK_FLAG_MIXER_GET_CUR_BROKEN (without this
> patch) breaks mixer change notifications? I.e., tune the volume with the
> buttons/knobs on the device and see if the audio stack reflects the
> change. I guess it will break the notifications, but I would still like
> to wait for your confirmation.
>
> Thanks,
> Rong
>
>> Therefore Mic SET_RES alone does not explain the complete snd-usb-audio
>> failure in all device configurations. There must be another difference in
>> the full snd-usb-audio initialization path when the boom is attached.
>>
>> The separate Playback -64 dB minimum issue I reported remains unchanged:
>> -64 dB is ineffective, -63 dB works, and attempting -64 dB does not prevent
>> subsequent valid Playback SET_CUR requests from working.
>>
>> Sorry for not noticing the detachable-microphone state earlier. I wanted to
>> send this correction as soon as I confirmed it.
>>
>> I still have the usbmon/pcapng captures and can run further targeted tests
>> if useful.
>>
>> Thanks,
>> Alexander
>>
>> Am 18.08.2026 um 16:41 schrieb Alexander Niemeyer:
>>> Hi Rong,
>>>
>>> I think we found the reason for the different behavior.
>>>
>>> I reproduced the snd-usb-audio initialization sequence step by step
>>> with direct libusb UAC1 control transfers and isolated the problem to
>>> SET_RES on the *Mic Capture Volume control (Feature Unit 3)*.
>>>
>>> A fresh-device control test looks like this:
>>>
>>> Mic GET_RES = 256
>>> no SET_RES
>>> Playback:
>>> GET_CUR = -3840 (-15 dB)
>>> SET_CUR = -2048 (-8 dB)
>>> GET_CUR changes to -2048 after 68.0 ms
>>> Result: PASS
>>>
>>> After another power cycle, I repeated the same test but issued just
>>> *one* SET_RES request to the Mic Feature Unit first:
>>>
>>> Mic GET_RES before = 256
>>> Mic SET_RES(128) = success
>>> Mic GET_RES after = 256
>>> Playback:
>>> GET_CUR = -3840 (-15 dB)
>>> SET_CUR = -2048 (-8 dB)
>>> GET_CUR remains -3840 for more than 1200 ms
>>> Result: FAIL
>>>
>>> So a single successful |SET_RES(128)| on Feature Unit 3 is sufficient
>>> to make subsequent |SET_CUR| requests to the Playback Volume control
>>> on Feature Unit 2 ineffective.
>>>
>>> I also tested the complete Mic SET_RES sequence used by snd-usb-audio:
>>>
>>> SET_RES 128
>>> SET_RES 64
>>> SET_RES 32
>>> SET_RES 16
>>> SET_RES 8
>>> SET_RES 4
>>> SET_RES 2
>>> SET_RES 1
>>>
>>> All requests return success, while GET_RES remains 256. After that
>>> sequence, Playback SET_CUR also remains ineffective for more than 1200
>>> ms.
>>>
>>> Interestingly, the Mic control itself still works after this. In an
>>> ALSA-like Mic probe I could successfully change Mic Volume from 0 dB
>>> to -64 dB and then +1 dB, with GET_CUR reflecting those changes
>>> essentially immediately (~0.3 ms). Playback remained broken afterwards.
>>>
>>> I also checked whether SET_RES on the Playback Feature Unit itself
>>> causes the problem. It does not:
>>>
>>> Playback GET_RES = 256
>>> SET_RES 128 -> 64 -> 32 -> 16 -> 8 -> 4 -> 2 -> 1
>>> GET_RES still = 256
>>> Playback SET_CUR(-8 dB)
>>> GET_CUR changes successfully after 87.7 ms
>>>
>>> So the problematic operation appears specifically to be *SET_RES on
>>> the Mic Feature Unit affecting the Playback Feature Unit*.
>>>
>>> I also clarified the separate advertised-minimum issue:
>>>
>>> Playback SET_CUR(-64 dB):
>>> no change after >1200 ms
>>> followed by SET_CUR(-8 dB):
>>> works normally after 54.9 ms
>>> Playback SET_CUR(-63 dB):
>>> works after 75.8 ms
>>> followed by SET_CUR(-8 dB):
>>> works after 43.6 ms
>>>
>>> Therefore the broken -64 dB endpoint does not leave the device in the
>>> broken state; it is a separate issue. -63 dB works normally.
>>>
>>> I also captured usbmon/pcapng traces for both a working direct-libusb
>>> SET_CUR sequence and the failing snd-usb-audio initialization, so I
>>> can send those as well if they are useful.
>>>
>>> This also seems to explain why the sticky-check changes did not help:
>>> by the time snd-usb-audio reaches the Playback Volume sticky check,
>>> the earlier Mic SET_RES sanity test has already put the device into
>>> the state where Playback SET_CUR no longer takes effect.
>>>
>>> Let me know if you would like me to test a patch or capture any
>>> additional traces.
>>>
>>> Thanks,
>>> Alexander
>>>
>>>
>>> Am 16.08.2026 um 17:08 schrieb Rong Zhang:
>>>> Hi Alexander,
>>>>
>>>> On Sun, 2026-08-16 at 16:09 +0200, Alexander Niemeyer wrote:
>>>>> Hi Rong,
>>>>>
>>>>> Sure. The libusb tests were direct USB Audio Class 1 control transfers
>>>>> to the headset using libusb/PyUSB, not ALSA mixer operations.
>>>>>
>>>>> I accessed Feature Unit 2 on AudioControl interface 0, master
>>>>> channel 0,
>>>>> with the UAC1 Volume control selector:
>>>>>
>>>>> wValue = 0x0200 /* Volume control, master channel */
>>>>> wIndex = 0x0200 /* Feature Unit 2, interface 0 */
>>>>>
>>>>> I used the standard class-specific requests directly, including
>>>>> GET_CUR,
>>>>> GET_MIN, GET_MAX, GET_RES and SET_CUR, with signed 16-bit little-endian
>>>>> volume values in 1/256 dB units.
>>>>>
>>>>> The device reported:
>>>>>
>>>>> GET_CUR: 0 ( 0 dB in that test)
>>>>> GET_MIN: -16384 (-64 dB)
>>>>> GET_MAX: 0 ( 0 dB)
>>>>> GET_RES: 256 ( 1 dB)
>>>>>
>>>>> For the timing tests I issued SET_CUR for a target value and then
>>>>> repeatedly queried GET_CUR until the value changed or the timeout
>>>>> expired.
>>>>>
>>>>> Valid values became visible after roughly:
>>>>>
>>>>> -1 dB ~81 ms
>>>>> -2 dB ~52 ms
>>>>> -4 dB ~47 ms
>>>>> -8 dB ~47 ms
>>>>> -16 dB ~52 ms
>>>>> -32 dB ~47 ms
>>>>>
>>>>> The advertised -64 dB minimum behaved differently: SET_CUR returned
>>>>> successfully, but GET_CUR did not change even after 1000 ms.
>>>>>
>>>>> To access the AudioControl interface with libusb, I unbound the
>>>>> AudioControl interface from snd-usb-audio for the duration of the test.
>>>>>
>>>>> I did not intentionally open a playback stream during those libusb
>>>>> tests. Because the AudioControl interface had been unbound from
>>>>> snd-usb-audio, I also do not believe there was an active ALSA playback
>>>>> stream at that point.
>>>> Thanks for the information.
>>>>
>>>> Unfortunately, I still don't exactly see why the device behaved
>>>> differently when GET_CUR/SET_CUR requests were sent from snd-usb-audio
>>>> compared to your libusb tests.
>>>>
>>>> snd-usb-audio also tries SET_RES to test the sanity of GET_RES. Could
>>>> you
>>>> test if it breaks your device's GET_CUR?
>>>>
>>>> Maybe comparing them with usbmon can show some clues. You can use
>>>> Wireshark to sniff /dev/usbmon*.
>>>>
>>>> Hint: a Thunderbolt port usually corresponds to a dedicated USB root
>>>> hub.
>>>> If you have one, plug the device to it to get pure usbmon trace results
>>>> with no noisy URBs from other devices.
>>>>
>>>> Thanks,
>>>> Rong
>>>>
>>>>> If the open-stream state is important, I can repeat the experiment
>>>>> specifically controlling for playback-stream-open versus
>>>>> playback-stream-closed.
>>>>>
>>>>> Thanks,
>>>>> Alexander
>>>>>
>>>>> Am 16.08.2026 um 15:50 schrieb Rong Zhang:
>>>>>> Hi Alexander,
>>>>>>
>>>>>> On Sun, 2026-08-16 at 07:14 +0200, Alexander Niemeyer wrote:
>>>>>>> Hi Rong,
>>>>>>>
>>>>>>> I tested the sticky-check part of your patch on the Logitech PRO X
>>>>>>> Wireless (046d:0aba) on Fedora 44, kernel 7.1.8-200.fc44.x86_64.
>>>>>>>
>>>>>>> Since your patch is based on a newer tree, I used a minimal
>>>>>>> backport of
>>>>>>> the new ~16-value / 10 ms sticky-check logic to the 7.1.8 code. The
>>>>>>> GET_CUR-broken handling from the newer tree was not included; GET_CUR
>>>>>>> itself succeeds on this device.
>>>>>>>
>>>>>>> Unfortunately, the playback control is still classified as sticky:
>>>>>>>
>>>>>>> 2:0: sticky mixer values (-16384/0/256 => -3840), disabling
>>>>>>>
>>>>>>> I then instrumented the check and tried an additional diagnostic:
>>>>>>> after
>>>>>>> every successful SET_CUR, wait 100 ms and perform another GET_CUR
>>>>>>> before
>>>>>>> issuing the next SET_CUR.
>>>>>>>
>>>>>>> For the playback volume, the saved value was -3840 and GET_CUR
>>>>>>> remained
>>>>>>> at -3840 for every tested value, even after 100 ms, for example:
>>>>>>>
>>>>>>> test=-15104 immediate=-3840 after100ms=-3840
>>>>>>> test=-13824 immediate=-3840 after100ms=-3840
>>>>>>> test=-3584 immediate=-3840 after100ms=-3840
>>>>>>> test=-2304 immediate=-3840 after100ms=-3840
>>>>>>> test=-1024 immediate=-3840 after100ms=-3840
>>>>>>> test=0 immediate=-3840 after100ms=-3840
>>>>>>>
>>>>>>> So in this case the issue does not appear to be simply that the
>>>>>>> accumulated 10 ms sleeps are too short. During the probe-time sticky
>>>>>>> check, SET_CUR succeeds but GET_CUR for the playback control remains
>>>>>>> unchanged even when each SET_CUR is given 100 ms before the next one.
>>>>>>>
>>>>>>> This differs from my previous direct libusb tests with the
>>>>>>> AudioControl
>>>>>>> interface unbound, where valid SET_CUR values became visible through
>>>>>>> GET_CUR after roughly 47–81 ms.
>>>>>> Really interesting. Maybe the mixer changes its value only when
>>>>>> there is
>>>>>> an opened playback stream.
>>>>>>
>>>>>> Could you clarify your "libusb tests"?
>>>>>>
>>>>>> Thanks,
>>>>>> Rong
>>>>>>
>>>>>>> The first debug line I saw with |saved=0| was from the Mic Capture
>>>>>>> Volume control; that control changed immediately and returned as
>>>>>>> non-sticky. The sequence above with |saved=-3840| is the
>>>>>>> problematic PCM
>>>>>>> Playback Volume control.
>>>>>>>
>>>>>>> I'd be happy to test another version or run additional diagnostics if
>>>>>>> useful.
>>>>>>>
>>>>>>> Best regards,
>>>>>>> Alexander
>>>>>>>
>>>>>>>
>>>>>>> Am 15.08.2026 um 23:47 schrieb Rong Zhang:
>>>>>>>> Some mixers are asynchronous, and some have broken min/max. They are
>>>>>>>> mistakenly considered sticky due to how the check is implemented.
>>>>>>>>
>>>>>>>> Check sticky mixers more precisely by checking approximately 16
>>>>>>>> values
>>>>>>>> and adding a msleep(10) between each check, so that asynchronous
>>>>>>>> mixers
>>>>>>>> have enough time to change the value and mixers with broken
>>>>>>>> min/max are
>>>>>>>> checked properly. Additionally, mark GET_CUR as broken when
>>>>>>>> get_cur_mix_raw() fails, instead of returning successfully.
>>>>>>>>
>>>>>>>> Reported-by: Alexander Niemeyer<adventureFAN@gmx.de>
>>>>>>>> Closes:https://lore.kernel.org/r/6262cbbd-d1f2-4c9d-a1c7-9c5d12636f4b@gmx.de
>>>>>>>>
>>>>>>>> Signed-off-by: Rong Zhang<i@rong.moe>
>>>>>>>> ---
>>>>>>>>      sound/usb/mixer.c | 51
>>>>>>>> ++++++++++++++++++++++++++++++++++++++++++++-------
>>>>>>>>      1 file changed, 44 insertions(+), 7 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
>>>>>>>> index 703c118f9d4e..3d0f97730a06 100644
>>>>>>>> --- a/sound/usb/mixer.c
>>>>>>>> +++ b/sound/usb/mixer.c
>>>>>>>> @@ -1256,22 +1256,59 @@ static void init_cur_mix_raw(struct
>>>>>>>> usb_mixer_elem_info *cval, int ch, int idx)
>>>>>>>>      static int check_sticky_volume_control(struct
>>>>>>>> usb_mixer_elem_info *cval,
>>>>>>>>                             int channel, int saved)
>>>>>>>>      {
>>>>>>>> -    int sticky_test_values[] = { cval->min, cval->max };
>>>>>>>> -    int test, check, i;
>>>>>>>> +    int test, check, res;
>>>>>>>> +
>>>>>>>> +    /*
>>>>>>>> +     * Check approximately 16 values (15 intervals).
>>>>>>>> +     * If the resolution is not fine enough, check fewer values.
>>>>>>>> +     */
>>>>>>>> +    res = DIV_ROUND_UP(cval->max - cval->min, 15);
>>>>>>>> +    res = res ? roundup(res, cval->res) : cval->res;
>>>>>>>> +
>>>>>>>> +    /*
>>>>>>>> +     * If (cval->max - cval->min) is not a multiple of
>>>>>>>> cval->res, we still
>>>>>>>> +     * want to test cval->max anyway.
>>>>>>>> +     */
>>>>>>>> +    for (test = cval->min; test < cval->max + res; test += res) {
>>>>>>>> +        if (test > cval->max)
>>>>>>>> +            test = cval->max;
>>>>>>>>      -    for (i = 0; i < ARRAY_SIZE(sticky_test_values); i++) {
>>>>>>>> -        test = sticky_test_values[i];
>>>>>>>>              if (test == saved)
>>>>>>>>                  continue;
>>>>>>>>                  /* Assume non-sticky on failure. */
>>>>>>>> -        if (snd_usb_set_cur_mix_value(cval, channel, 0, test) ||
>>>>>>>> -            get_cur_mix_raw(cval, channel, &check) ||
>>>>>>>> -            check != saved) /* SET_CUR effective, non-sticky. */
>>>>>>>> +        if (snd_usb_set_cur_mix_value(cval, channel, 0, test))
>>>>>>>> +            return 0;
>>>>>>>> +
>>>>>>>> +        if (get_cur_mix_raw(cval, channel, &check))
>>>>>>>> +            goto get_cur_broken;
>>>>>>>> +        if (check != saved) /* SET_CUR effective, non-sticky. */
>>>>>>>>                  return 0;
>>>>>>>> +
>>>>>>>> +        /*
>>>>>>>> +         * Leave some time for asynchronous mixers to change the
>>>>>>>> value.
>>>>>>>> +         *
>>>>>>>> +         * Note that there is no need to wait between SET_CUR and
>>>>>>>> +         * GET_CUR, as we don't care whether the GET_CUR value
>>>>>>>> matches
>>>>>>>> +         * the SET_CUR one. IOW, what we expect is just a
>>>>>>>> GET_CUR value
>>>>>>>> +         * differing from the saved one.
>>>>>>>> +         *
>>>>>>>> +         * Mixers of most devices are synchronous. The should have
>>>>>>>> +         * returned early without extra sleep. Asynchronous
>>>>>>>> mixers will
>>>>>>>> +         * return once the accumulated time is enough for them
>>>>>>>> to change
>>>>>>>> +         * the value.
>>>>>>>> +         */
>>>>>>>> +        msleep(10);
>>>>>>>>          }
>>>>>>>>      +    /* Check again after the last msleep(). */
>>>>>>>> +    if (get_cur_mix_raw(cval, channel, &check))
>>>>>>>> +        goto get_cur_broken;
>>>>>>>> +    if (check != saved)
>>>>>>>> +        return 0;
>>>>>>>> +
>>>>>>>>          if (cval->head.mixer->chip->quirk_flags &
>>>>>>>> QUIRK_FLAG_MIXER_GET_CUR_BROKEN) {
>>>>>>>> +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),
>>>>>>>>
>>>>>>>> ---
>>>>>>>> base-commit: 3eb40771c00a8488fa6ed2cc1fe203477908bf38
>>>>>>>> change-id: 74676fce-uac-precise-sticky-check-94474a22b57d
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>> Rong
>>>>>>>>