[PATCH] ALSA: usb-audio: Apply implicit feedback mode for BOSS devices

[Keith A. Milner]

On Tuesday, 20 April 2021 05:20:57 BST Lucas wrote:
> Keith, if it's anything like the Roland devices I've tested with this
> long-awaited patch, could you show the JS-8's "lsusb -v"?

Output pasted further down.

> 
> For me, silence due to the wrong line takes the form of unheard output
> playback, while still working for input capture, so I'm not sure this has
> any bearing on your issue.

When testing Takashi-san's earlier patches, I had a mixture of experiences 
including (depending on the patch) some devices recording silence, some 
playing back silence, and some where the record would lock up until playback 
was started (or vice versa).

> 
> Takashi Iwai has indicated a likely connection between needing the
> IMPLICIT_FB_BOTH_DEVICE line if there's "Asynchronous" "Synch Type" for
> both input and output endpoints.  Otherwise, possibly, it should be
> reverted to IMPLICIT_FB_FIXED_DEVICE for the JS-8.

As you can see, this has "Asynchronous" "Synch Type" on EP4 IN and EP 5 OUT, 
so I don't think it's this.

Bus 001 Device 007: ID 0582:0109 Roland Corp. eBand JS-8
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass          255 Vendor Specific Class
  bDeviceSubClass         0 
  bDeviceProtocol       255 
  bMaxPacketSize0        64
  idVendor           0x0582 Roland Corp.
  idProduct          0x0109 eBand JS-8
  bcdDevice            0.01
  iManufacturer           1 BOSS
  iProduct                2 JS-8
  iSerial                 0 
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength       0x00a7
    bNumInterfaces          3
    bConfigurationValue     1
    iConfiguration          0 
    bmAttributes         0xc0
      Self Powered
    MaxPower                0mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      2 
      bInterfaceProtocol      2 
      iInterface              0 
      ** UNRECOGNIZED:  06 24 f1 01 00 00
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       1
      bNumEndpoints           1
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      2 
      bInterfaceProtocol      2 
      iInterface              0 
      ** UNRECOGNIZED:  07 24 01 01 00 01 00
      ** UNRECOGNIZED:  0b 24 02 01 02 04 18 01 44 ac 00
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x05  EP 5 OUT
        bmAttributes            5
          Transfer Type            Isochronous
          Synch Type               Asynchronous
          Usage Type               Data
        wMaxPacketSize     0x0070  1x 112 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      2 
      bInterfaceProtocol      1 
      iInterface              0 
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       1
      bNumEndpoints           1
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      2 
      bInterfaceProtocol      1 
      iInterface              0 
      ** UNRECOGNIZED:  07 24 01 07 00 01 00
      ** UNRECOGNIZED:  0b 24 02 01 02 04 18 01 44 ac 00
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x84  EP 4 IN
        bmAttributes           37
          Transfer Type            Isochronous
          Synch Type               Asynchronous
          Usage Type               Implicit feedback Data
        wMaxPacketSize     0x0070  1x 112 bytes
        bInterval               1
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        2
      bAlternateSetting       0
      bNumEndpoints           2
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      3 
      bInterfaceProtocol      0 
      iInterface              0 
      ** UNRECOGNIZED:  06 24 f1 02 02 02
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x82  EP 2 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        2
      bAlternateSetting       1
      bNumEndpoints           2
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      3 
      bInterfaceProtocol      0 
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               1
Device Qualifier (for other device speed):
  bLength                10
  bDescriptorType         6
  bcdUSB               2.00
  bDeviceClass            8 Mass Storage
  bDeviceSubClass         6 SCSI
  bDeviceProtocol        80 Bulk-Only
  bMaxPacketSize0        64
  bNumConfigurations      0
can't get debug descriptor: Resource temporarily unavailable
Device Status:     0x0001
  Self Powered

Regards,

Keith