Mixer regression with usb soundcard

[Mauro Santos <registo.mailling@gmail.com>]

On 18-12-2017 21:56, Mauro Santos wrote:
> On 18-12-2017 19:30, Takashi Iwai wrote:
>> On Mon, 18 Dec 2017 20:10:44 +0100,
>> Mauro Santos wrote:
>>>
>>> On 18-12-2017 17:50, Jaejoong Kim wrote:
>>>> Mauro,
>>>>
>>>> Could you please try debug patch(I also attach the patch file)?
>>>
>>> With the attached patch I get the following when plugging in the usb dac
>>> directly to a usb3 port:
>>> [   54.391539] usb 1-2: new full-speed USB device number 7 using xhci_hcd
>>> [   54.514996] usb 1-2: device descriptor read/64, error -71
>>> [   54.849808] input: HiFimeDIY Audio HiFimeDIY DAC as
>>> /devices/pci0000:00/0000:00:14.0/usb1/1-2/1-2:1.0/0003:1852:7022.0003/input/input20
>>> [   54.850168] hid-generic 0003:1852:7022.0003: input,hidraw2: USB HID
>>> v1.00 Device [HiFimeDIY Audio HiFimeDIY DAC] on usb-0000:00:14.0-2/input0
>>> [   54.950421] usb 1-2: [DEBUG] nameid:0, len:0
>>> [   54.950426] usb 1-2: [DEBUG] len:3, get_term_name:PCM
>>> [   54.950429] usb 1-2: [11] SU [PCM] items = 2
>>> [   54.950985] usbcore: registered new interface driver snd-usb-audio
>>
>> Hmm, the driver get the supposedly correct name string here, so I see
>> no flaw, so far.
>>
>> Could you put the similar debug prints after reverting the commit and
>> compare?  Or, at minimum, you can enable simply the kernel debug
>> prints like below:
>>
>>   % echo "file sound/usb/mixer.c +p" > /sys/kernel/debug/dynamic_debug_control
>>
>> and re-plug the device.
>>
>> Also, could you attach the output of "amixer contents" on both working
>> and non-working kernels?
>>
> 
> I have compiled a new kernel where I have reverted the commit and I've
> added the debug output based on your last debug patch. I attach the
> patch that reverts the changes and adds the debug output just in case
> anyone wants to do a sanity check on it (don't mind the indentation I
> think I botched that).
> 
> With the debug patches I get no extra output when echoing to the
> dynamic_debug/control file, I guess that's expected.
> 
Turns out there is some output, I can't echo and plug, I need to plug,
echo, replug. Dmesg outputs are attached.

> I attach the dmesg and amixer outputs for the case without revert plus
> debug (bad) and revert plus debug (good).
> 
> One change does jump out:
> 
> bad:  usb 1-2: [11] SU [PCM] items = 2
> good: usb 1-2: [11] SU [PCM Capture Source] items = 2
>