[alsa-devel] Dell USB audio driver workaround

[Hui Wang]

On 06/14/2017 11:50 PM, Takashi Iwai wrote:
> On Wed, 14 Jun 2017 04:29:13 +0200,
> Hui Wang wrote:
>> In this thread, I added tanuk at iki.fi and svillar at igalia.com since they
>> reported or discussed similar bugs recently
>> (https://www.spinics.net/lists/alsa-devel/msg62460.html and
>> https://bugs.freedesktop.org/show_bug.cgi?id=100711).
>>
>> Right now, we are trying to enable the USB audio for the Dell dock
>> stations TB16[1] and WD15[2]. For usb audio part, they have the same
>> design, they use realtek alc4020 USB bridge and alc3263 codec, and
>> there are one headset jack on the front panel and one speaker output
>> jack on the rear panel, but due to some reason (probably it is the
>> firmware's problem), the alsa mixers can't reflect there is speaker or
>> headset on them, as a result the pulseaudio can't handle the headset
>> or speaker correctly.
>>
>> Right now, the pulseaudio can find a playback device and a record
>> device, it is the output and input device for that headset jack, but
>> pulseaudio does not think they are headphone and Mic, pulseaudio think
>> they are just USB analog output and input devices; for the speaker
>> jack, the pulseaudio can't find it at all. so through pulseaudio, we
>> can't play any sound to that speaker jack.
>>
>> This is the output and input devices listed by alsa-utils:
>>
>> !!Aplay/Arecord output
>> !!--------------------
>>
>> APLAY
>>
>> **** List of PLAYBACK Hardware Devices ****
>> ...
>> card 1: Audio [USB Audio], device 0: USB Audio [USB Audio]
>>    Subdevices: 1/1
>>    Subdevice #0: subdevice #0
>> card 1: Audio [USB Audio], device 1: USB Audio [USB Audio #1]
>>    Subdevices: 1/1
>>    Subdevice #0: subdevice #0
>>
>> ARECORD
>>
>> **** List of CAPTURE Hardware Devices ****
>> ...
>> card 1: Audio [USB Audio], device 0: USB Audio [USB Audio]
>>    Subdevices: 1/1
>>    Subdevice #0: subdevice #0
>>
>>
>>
>>
>> And we can use alsa-utils command to play sound to speaker jack:
>> $ aplay -D plughw:CARD=1,DEV=1 /usr/share/sounds/speech-dispatcher/test.wav
>>
>> I don't know how to fix this problem in the kernel driver, if we can
>> let driver export standard mixers, this issue will be fixed. But it
>> looks like the mixers depend on the firmware, we can't change the
>> firmware, so probably we can't fix it in the kernel driver.
> Right, there are multiple problems.  One is the firmware problem as
> you mentioned.  With the old firmware, the USB descriptor and the
> behavior of the device are unstable / inconsistent.
>
> Even with the fixed firmware, USB audio driver in general may assign
> PCM streams depending on the descriptor, and the name can't be set
> consistently per purpose.  So, it can't appear like "Headphone Stream"
> or "Line Out Stream".  The only sensible way I can think of is to
> apply some static mappings for creation of the streams, like the mixer
> mapping for some devices.
>
> This is, however, only a part of the iceberg.  A bigger problem is
> that USB-audio driver doesn't handle the jack detection usually by
> itself.  The jack detection part belongs to the HID, and it should be
> handled by a different driver.  That is, if any, PA would need to
> resolve the corresponding input device and deal with the input events.
> That's a mess.
Yes, the USB-audio jack detection is a bigger problem. Since the current 
USB-audio driver does not export JACK to the userspace, the PA does not 
check jack plugging/unplugging at all. If a USB-audio adapter is plugged 
in, the PA will treat it as a USB headpone+microphone, will think this 
device is ready to work, then users can select this sound card via UI 
program to play or record sound.

>> Another way to fix it is to add a conf to pulseaudio, in the conf, we
>> add one profile for headset(hw:%f,0,0) and one profile for
>> speaker(hw:%f,1,0), this is the draft patch I sent to
>> pulseaudio-discuss mail list:
>> https://lists.freedesktop.org/archives/pulseaudio-discuss/2017-May/028252.html
>>
>> Do you have any idea to fix this problem? Thanks in advance. And below
>> are some logs I collected on the TB16, if you need more logs, just
>> tell me, I will collect them for you.
> I'm in favor of the configuration specific to the device.  Still we'd
> need a few fixups in the kernel side, too.  Other "perfect solutions"
> would be hard to achieve, I'm afraid.

Thanks for your advice.

Through PA, users can't select speaker (hw:%f,1,0) to work, this is a 
more urgent problem.

Hi Tanu,

If you have time, could you please take a look at the patch I sent to 
pulseaudio-discuss?


Thanks,
Hui.

>
> thanks,
>
> Takashi
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