[PATCH] ALSA: usb-audio: allow -EPIPE errors for some v2 messages

[Takashi Iwai]

On Sun, 10 Oct 2021 14:22:41 +0200,
Greg Kroah-Hartman wrote:
> 
> The Schiit Hel device does not like to respond to all get_ctl_value_v2()
> requests for some reason.  This used to work in older kernels, but now
> with more strict checking, this failure causes the device to fail to
> work.
> 
> Cc: Jaroslav Kysela <perex at perex.cz>
> Cc: Takashi Iwai <tiwai at suse.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> ---
> 
> This fixes the Shiit Hel device that I have.  It used to work on older
> kernels (a year ago?), but stopped working for some reason and I didn't
> take the time to track it down.  This change fixes the issue for me, but
> feels wrong for some reason.  At least now I can use the device as a
> headphone driver, much better than the built-in one for my current
> machine...
> 
> If needed, I can take the time to do bisection to track down the real
> issue here, it might be due to stricter endpoint checking in the USB
> core, but that feels wrong somehow.
> 
> Here's the debugfs USB output for this device, showing the endpoints:
> 
> T:  Bus=07 Lev=02 Prnt=02 Port=01 Cnt=01 Dev#=  5 Spd=480 MxCh= 0
> D:  Ver= 2.00 Cls=ef(misc ) Sub=02 Prot=01 MxPS=64 #Cfgs=  1
> P:  Vendor=30be ProdID=0101 Rev=01.02
> S:  Manufacturer=Schiit Audio
> S:  Product=Schiit Hel
> C:  #Ifs= 4 Cfg#= 1 Atr=c0 MxPwr=0mA
> I:  If#= 0 Alt= 0 #EPs= 1 Cls=01(audio) Sub=01 Prot=20 Driver=snd-usb-audio
> E:  Ad=8f(I) Atr=03(Int.) MxPS=   6 Ivl=1ms
> I:  If#= 1 Alt= 1 #EPs= 2 Cls=01(audio) Sub=02 Prot=20 Driver=snd-usb-audio
> E:  Ad=05(O) Atr=05(Isoc) MxPS= 104 Ivl=125us
> E:  Ad=85(I) Atr=11(Isoc) MxPS=   4 Ivl=1ms
> I:  If#= 2 Alt= 1 #EPs= 1 Cls=01(audio) Sub=02 Prot=20 Driver=snd-usb-audio
> E:  Ad=88(I) Atr=05(Isoc) MxPS= 156 Ivl=125us
> I:  If#= 3 Alt= 0 #EPs= 1 Cls=03(HID  ) Sub=00 Prot=00 Driver=usbhid
> E:  Ad=84(I) Atr=03(Int.) MxPS=  16 Ivl=1ms
> 
> Any other suggestions to fix this are welcome.

Could you show the exact error messages and lsusb -v output?
We may paper over only the problematic node instead.


thanks,

Takashi