Re: kernel 5.4.11: problems with usb sound cards

[Johan Hovold]

[ +CC: Takashi ]

On Sat, Feb 01, 2020 at 01:26:16PM -0300, edes wrote:
> 
> > Can you please post the output of "lsusb -v" for this device on 5.4.10
> > and 5.4.11, respectively?
> 
> 
> Hello, thanks for your prompt response. Please see attached (I hope that
> is OK) the output of lsusb -v on both 5.4.10 and 5.4.11.
> 
> The device in question is the Sound Devices USBPre2, Bus 003 Device 004:
> ID 0926:0202, beginning at line 808.

Ok, so the device has a broken altsetting 3 for interface 1, where
endpoint 0x85 is declared as an isochronous endpoint, despite being used
by interface 2 as an audio endpoint:

    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       3
      bNumEndpoints           2
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      0 
      bInterfaceProtocol      0 
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x85  EP 5 IN
        bmAttributes            5
          Transfer Type            Isochronous
          Synch Type               Asynchronous
          Usage Type               Data
        wMaxPacketSize     0x0126  1x 294 bytes
        bInterval               1

...

    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        2
      bAlternateSetting       1
      bNumEndpoints           1
      bInterfaceClass         1 Audio
      bInterfaceSubClass      2 Streaming
      bInterfaceProtocol      0 
      iInterface              0 
      AudioStreaming Interface Descriptor:
        bLength                 7
        bDescriptorType        36
        bDescriptorSubtype      1 (AS_GENERAL)
        bTerminalLink           4
        bDelay                  1 frames
        wFormatTag         0x0001 PCM
      AudioStreaming Interface Descriptor:
        bLength                26
        bDescriptorType        36
        bDescriptorSubtype      2 (FORMAT_TYPE)
        bFormatType             1 (FORMAT_TYPE_I)
        bNrChannels             2
        bSubframeSize           2
        bBitResolution         16
        bSamFreqType            6 Discrete
        tSamFreq[ 0]         8000
        tSamFreq[ 1]        16000
        tSamFreq[ 2]        24000
        tSamFreq[ 3]        32000
        tSamFreq[ 4]        44100
        tSamFreq[ 5]        48000
      Endpoint Descriptor:
        bLength                 9
        bDescriptorType         5
        bEndpointAddress     0x85  EP 5 IN
        bmAttributes            5
          Transfer Type            Isochronous
          Synch Type               Asynchronous
          Usage Type               Data
        wMaxPacketSize     0x0126  1x 294 bytes
        bInterval               4
        bRefresh                0
        bSynchAddress           0
        AudioStreaming Endpoint Descriptor:
          bLength                 7
          bDescriptorType        37
          bDescriptorSubtype      1 (EP_GENERAL)
          bmAttributes         0x01
            Sampling Frequency
          bLockDelayUnits         2 Decoded PCM samples
          wLockDelay         0x0000


Since commit 3e4f8e21c4f2 ("USB: core: fix check for duplicate
endpoints") USB core ignores any duplicate endpoints, but in this case
we really want to ignore the first instance.

Can you try the below patch, which adds a blacklist quirk for the broken
endpoint descriptor?

Note that the broken altsetting probably should be using endpoint 0x81
just like the other altsettings for that interface, but hopefully you
don't really use this setting so that simply ignoring the endpoint will
make the device work again.

Interestingly enough, in your lsusb output from 5.4.11, the device
reports a second configuration in which this broken altsetting doesn't
exist. Switching to that config should also make the problem go away.

Johan