[alsa-devel] Dell USB audio driver workaround

[Takashi Iwai]

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.

> 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,

Takashi