[alsa-devel] Mixer regression with usb soundcard

[Takashi Iwai]

On Tue, 19 Dec 2017 02:04:51 +0100,
Mauro Santos wrote:
> 
> On 18-12-2017 22:48, Takashi Iwai wrote:
> > On Mon, 18 Dec 2017 22:56:07 +0100,
> > 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.
> >>
> >> 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
> > 
> > Thanks, that explains what went wrong.  The commit dropped the brace
> > at the if-line, and it ended up with the lack of suffix unless
> > get_term_name() fails.
> > 
> > The fix patch is below.  Could you check whether it cures the issue?
> 
> This patch does seem to work fine for me, I can see all the mixer
> controls for the usb soundcard/dac.
> 
> For good measure I have also tested with a couple of usb headsets and I
> didn't see anything amiss (they don't have any "Capture Source" controls
> though).
> 
> Thank you for looking into this and fixing it.

Good to hear, I queued the fix to for-linus branch.
I'm going to send a pull request for rc5.


thanks,

Takashi