USB Audio Descriptor - multiple devices, one usb connection

mrecoskie · ‎02-14-2022

Hi,

I am attempting to manually create a USB descriptor for two devices behind a single USB Audio Class 2.0 connection. Does anyone know whether or not the Terminals, Clock and Unit should all be unique IDs when utilizing multiple Interface Association Descriptors (IAD)? I would assume so. Does anyone have a working example of this type of descriptor?

Below is my attempt however the linux host has complaints. Is there someone with experience in this area to review the descriptor below? Thank you.

Mark

Bus 001 Device 029: ID 1fc9:00a4 NXP Semiconductors

Device Descriptor:

bLength 18

bDescriptorType 1

bcdUSB 2.00

bDeviceClass 239 Miscellaneous Device

bDeviceSubClass 2

bDeviceProtocol 1 Interface Association

bMaxPacketSize0 64

idVendor 0x1fc9 NXP Semiconductors

idProduct 0x00a4

bcdDevice 1.01

iManufacturer 1

iProduct 2

iSerial 0

bNumConfigurations 1

Configuration Descriptor:

bLength 9

bDescriptorType 2

wTotalLength 0x01f3

bNumInterfaces 6

bConfigurationValue 1

iConfiguration 0

bmAttributes 0xc0

Self Powered

MaxPower 500mA

Interface Association:

bLength 8

bDescriptorType 11

bFirstInterface 0

bInterfaceCount 3

bFunctionClass 1 Audio

bFunctionSubClass 0

bFunctionProtocol 32

iFunction 0

Interface Descriptor:

bLength 9

bDescriptorType 4

bInterfaceNumber 0

bAlternateSetting 0

bNumEndpoints 0

bInterfaceClass 1 Audio

bInterfaceSubClass 1 Control Device

bInterfaceProtocol 32

iInterface 0

AudioControl Interface Descriptor:

bLength 9

bDescriptorType 36

bDescriptorSubtype 1 (HEADER)

bcdADC 2.00

bCategory 4

wTotalLength 0x006f

bmControls 0x00

AudioControl Interface Descriptor:

bLength 8

bDescriptorType 36

bDescriptorSubtype 10 (CLOCK_SOURCE)

bClockID 16

bmAttributes 3 Internal programmable clock

bmControls 0x07

Clock Frequency Control (read/write)

Clock Validity Control (read-only)

bAssocTerminal 0

iClockSource 0

AudioControl Interface Descriptor:

bLength 17

bDescriptorType 36

bDescriptorSubtype 2 (INPUT_TERMINAL)

bTerminalID 1

wTerminalType 0x0201 Microphone

bAssocTerminal 0

bCSourceID 16

bNrChannels 2

bmChannelConfig 0x00000003

Front Left (FL)

Front Right (FR)

iChannelNames 0

bmControls 0x0000

iTerminal 0

AudioControl Interface Descriptor:

bLength 18

bDescriptorType 36

bDescriptorSubtype 6 (FEATURE_UNIT)

bUnitID 2

bSourceID 1

bmaControls(0) 0x00000000

bmaControls(1) 0x00000000

bmaControls(2) 0x00000000

iFeature 0

AudioControl Interface Descriptor:

bLength 12

bDescriptorType 36

bDescriptorSubtype 3 (OUTPUT_TERMINAL)

bTerminalID 3

wTerminalType 0x0101 USB Streaming

bAssocTerminal 0

bSourceID 2

bCSourceID 16

bmControls 0x0000

iTerminal 0

AudioControl Interface Descriptor:

bLength 17

bDescriptorType 36

bDescriptorSubtype 2 (INPUT_TERMINAL)

bTerminalID 4

wTerminalType 0x0101 USB Streaming

bAssocTerminal 0

bCSourceID 16

bNrChannels 2

bmChannelConfig 0x00000003

Front Left (FL)

Front Right (FR)

iChannelNames 0

bmControls 0x0000

iTerminal 0

AudioControl Interface Descriptor:

bLength 18

bDescriptorType 36

bDescriptorSubtype 6 (FEATURE_UNIT)

bUnitID 5

bSourceID 4

bmaControls(0) 0x0000000f

Mute Control (read/write)

Volume Control (read/write)

bmaControls(1) 0x00000000

bmaControls(2) 0x00000000

iFeature 0

AudioControl Interface Descriptor:

bLength 12

bDescriptorType 36

bDescriptorSubtype 3 (OUTPUT_TERMINAL)

bTerminalID 6

wTerminalType 0x0301 Speaker

bAssocTerminal 0

bSourceID 5

bCSourceID 16

bmControls 0x0000

iTerminal 0

Interface Descriptor:

bLength 9

bDescriptorType 4

bInterfaceNumber 1

bAlternateSetting 0

bNumEndpoints 0

bInterfaceClass 1 Audio

bInterfaceSubClass 2 Streaming

bInterfaceProtocol 32

iInterface 0

Interface Descriptor:

bLength 9

bDescriptorType 4

bInterfaceNumber 1

bAlternateSetting 1

bNumEndpoints 1

bInterfaceClass 1 Audio

bInterfaceSubClass 2 Streaming

bInterfaceProtocol 32

iInterface 0

AudioStreaming Interface Descriptor:

bLength 16

bDescriptorType 36

bDescriptorSubtype 1 (AS_GENERAL)

bTerminalLink 3

bmControls 0x00

bFormatType 1

bmFormats 0x00000001

PCM

bNrChannels 2

bmChannelConfig 0x00000003

Front Left (FL)

Front Right (FR)

iChannelNames 0

AudioStreaming Interface Descriptor:

bLength 6

bDescriptorType 36

bDescriptorSubtype 2 (FORMAT_TYPE)

bFormatType 1 (FORMAT_TYPE_I)

bSubslotSize 2

bBitResolution 16

Endpoint Descriptor:

bLength 7

bDescriptorType 5

bEndpointAddress 0x83 EP 3 IN

bmAttributes 13

Transfer Type Isochronous

Synch Type Synchronous

Usage Type Data

wMaxPacketSize 0x00c4 1x 196 bytes

bInterval 4

AudioStreaming Endpoint Descriptor:

bLength 8

bDescriptorType 37

bDescriptorSubtype 1 (EP_GENERAL)

bmAttributes 0x00

bmControls 0x00

bLockDelayUnits 0 Undefined

wLockDelay 0x0000

Interface Descriptor:

bLength 9

bDescriptorType 4

bInterfaceNumber 2

bAlternateSetting 0

bNumEndpoints 0

bInterfaceClass 1 Audio

bInterfaceSubClass 2 Streaming

bInterfaceProtocol 32

iInterface 0

Interface Descriptor:

bLength 9

bDescriptorType 4

bInterfaceNumber 2

bAlternateSetting 1

bNumEndpoints 2

bInterfaceClass 1 Audio

bInterfaceSubClass 2 Streaming

bInterfaceProtocol 32

iInterface 0

AudioStreaming Interface Descriptor:

bLength 16

bDescriptorType 36

bDescriptorSubtype 1 (AS_GENERAL)

bTerminalLink 4

bmControls 0x00

bFormatType 1

bmFormats 0x00000001

PCM

bNrChannels 2

bmChannelConfig 0x00000003

Front Left (FL)

Front Right (FR)

iChannelNames 0

AudioStreaming Interface Descriptor:

bLength 6

bDescriptorType 36

bDescriptorSubtype 2 (FORMAT_TYPE)

bFormatType 1 (FORMAT_TYPE_I)

bSubslotSize 2

bBitResolution 16

Endpoint Descriptor:

bLength 7

bDescriptorType 5

bEndpointAddress 0x02 EP 2 OUT

bmAttributes 5

Transfer Type Isochronous

Synch Type Asynchronous

Usage Type Data

wMaxPacketSize 0x001c 1x 28 bytes

bInterval 1

AudioStreaming Endpoint Descriptor:

bLength 8

bDescriptorType 37

bDescriptorSubtype 1 (EP_GENERAL)

bmAttributes 0x00

bmControls 0x00

bLockDelayUnits 0 Undefined

wLockDelay 0x0000

Endpoint Descriptor:

bLength 7

bDescriptorType 5

bEndpointAddress 0x82 EP 2 IN

bmAttributes 17

Transfer Type Isochronous

Synch Type None

Usage Type Feedback

wMaxPacketSize 0x0004 1x 4 bytes

bInterval 4

Interface Association:

bLength 8

bDescriptorType 11

bFirstInterface 3

bInterfaceCount 3

bFunctionClass 1 Audio

bFunctionSubClass 0

bFunctionProtocol 32

iFunction 0

Interface Descriptor:

bLength 9

bDescriptorType 4

bInterfaceNumber 3

bAlternateSetting 0

bNumEndpoints 0

bInterfaceClass 1 Audio

bInterfaceSubClass 1 Control Device

bInterfaceProtocol 32

iInterface 0

AudioControl Interface Descriptor:

bLength 9

bDescriptorType 36

bDescriptorSubtype 1 (HEADER)

bcdADC 2.00

bCategory 4

wTotalLength 0x006f

bmControls 0x00

AudioControl Interface Descriptor:

bLength 8

bDescriptorType 36

bDescriptorSubtype 10 (CLOCK_SOURCE)

bClockID 17

bmAttributes 3 Internal programmable clock

bmControls 0x07

Clock Frequency Control (read/write)

Clock Validity Control (read-only)

bAssocTerminal 0

iClockSource 0

AudioControl Interface Descriptor:

bLength 17

bDescriptorType 36

bDescriptorSubtype 2 (INPUT_TERMINAL)

bTerminalID 7

wTerminalType 0x0201 Microphone

bAssocTerminal 0

bCSourceID 17

bNrChannels 2

bmChannelConfig 0x00000003

Front Left (FL)

Front Right (FR)

iChannelNames 0

bmControls 0x0000

iTerminal 0

AudioControl Interface Descriptor:

bLength 18

bDescriptorType 36

bDescriptorSubtype 6 (FEATURE_UNIT)

bUnitID 8

bSourceID 7

bmaControls(0) 0x0000000f

Mute Control (read/write)

Volume Control (read/write)

bmaControls(1) 0x00000000

bmaControls(2) 0x00000000

iFeature 0

AudioControl Interface Descriptor:

bLength 12

bDescriptorType 36

bDescriptorSubtype 3 (OUTPUT_TERMINAL)

bTerminalID 9

wTerminalType 0x0101 USB Streaming

bAssocTerminal 0

bSourceID 8

bCSourceID 17

bmControls 0x0000

iTerminal 0

AudioControl Interface Descriptor:

bLength 17

bDescriptorType 36

bDescriptorSubtype 2 (INPUT_TERMINAL)

bTerminalID 10

wTerminalType 0x0101 USB Streaming

bAssocTerminal 0

bCSourceID 17

bNrChannels 2

bmChannelConfig 0x00000003

Front Left (FL)

Front Right (FR)

iChannelNames 0

bmControls 0x0000

iTerminal 0

AudioControl Interface Descriptor:

bLength 18

bDescriptorType 36

bDescriptorSubtype 6 (FEATURE_UNIT)

bUnitID 11

bSourceID 10

bmaControls(0) 0x0000000f

Mute Control (read/write)

Volume Control (read/write)

bmaControls(1) 0x00000000

bmaControls(2) 0x00000000

iFeature 0

AudioControl Interface Descriptor:

bLength 12

bDescriptorType 36

bDescriptorSubtype 3 (OUTPUT_TERMINAL)

bTerminalID 12

wTerminalType 0x0301 Speaker

bAssocTerminal 0

bSourceID 11

bCSourceID 17

bmControls 0x0000

iTerminal 0

Interface Descriptor:

bLength 9

bDescriptorType 4

bInterfaceNumber 4

bAlternateSetting 0

bNumEndpoints 0

bInterfaceClass 1 Audio

bInterfaceSubClass 2 Streaming

bInterfaceProtocol 32

iInterface 0

Interface Descriptor:

bLength 9

bDescriptorType 4

bInterfaceNumber 4

bAlternateSetting 1

bNumEndpoints 1

bInterfaceClass 1 Audio

bInterfaceSubClass 2 Streaming

bInterfaceProtocol 32

iInterface 0

AudioStreaming Interface Descriptor:

bLength 16

bDescriptorType 36

bDescriptorSubtype 1 (AS_GENERAL)

bTerminalLink 9

bmControls 0x00

bFormatType 1

bmFormats 0x00000001

PCM

bNrChannels 2

bmChannelConfig 0x00000003

Front Left (FL)

Front Right (FR)

iChannelNames 0

AudioStreaming Interface Descriptor:

bLength 6

bDescriptorType 36

bDescriptorSubtype 2 (FORMAT_TYPE)

bFormatType 1 (FORMAT_TYPE_I)

bSubslotSize 2

bBitResolution 16

Endpoint Descriptor:

bLength 7

bDescriptorType 5

bEndpointAddress 0x85 EP 5 IN

bmAttributes 13

Transfer Type Isochronous

Synch Type Synchronous

Usage Type Data

wMaxPacketSize 0x00c0 1x 192 bytes

bInterval 1

AudioStreaming Endpoint Descriptor:

bLength 8

bDescriptorType 37

bDescriptorSubtype 1 (EP_GENERAL)

bmAttributes 0x00

bmControls 0x00

bLockDelayUnits 0 Undefined

wLockDelay 0x0000

Interface Descriptor:

bLength 9

bDescriptorType 4

bInterfaceNumber 5

bAlternateSetting 0

bNumEndpoints 0

bInterfaceClass 1 Audio

bInterfaceSubClass 2 Streaming

bInterfaceProtocol 32

iInterface 0

Interface Descriptor:

bLength 9

bDescriptorType 4

bInterfaceNumber 5

bAlternateSetting 1

bNumEndpoints 2

bInterfaceClass 1 Audio

bInterfaceSubClass 2 Streaming

bInterfaceProtocol 32

iInterface 0

AudioStreaming Interface Descriptor:

bLength 16

bDescriptorType 36

bDescriptorSubtype 1 (AS_GENERAL)

bTerminalLink 10

bmControls 0x00

bFormatType 1

bmFormats 0x00000001

PCM

bNrChannels 2

bmChannelConfig 0x00000003

Front Left (FL)

Front Right (FR)

iChannelNames 0

AudioStreaming Interface Descriptor:

bLength 6

bDescriptorType 36

bDescriptorSubtype 2 (FORMAT_TYPE)

bFormatType 1 (FORMAT_TYPE_I)

bSubslotSize 2

bBitResolution 16

Endpoint Descriptor:

bLength 7

bDescriptorType 5

bEndpointAddress 0x04 EP 4 OUT

bmAttributes 5

Transfer Type Isochronous

Synch Type Asynchronous

Usage Type Data

wMaxPacketSize 0x00c4 1x 196 bytes

bInterval 1

AudioStreaming Endpoint Descriptor:

bLength 8

bDescriptorType 37

bDescriptorSubtype 1 (EP_GENERAL)

bmAttributes 0x00

bmControls 0x00

bLockDelayUnits 0 Undefined

wLockDelay 0x0000

Endpoint Descriptor:

bLength 7

bDescriptorType 5

bEndpointAddress 0x84 EP 4 IN

bmAttributes 17

Transfer Type Isochronous

Synch Type None

Usage Type Feedback

wMaxPacketSize 0x0008 1x 8 bytes

bInterval 16

mrecoskie · ‎02-16-2022

Below are some of the messages Linux is reporting. I am digging through the kernel code to try to decode them.

[233102.781298] usb 1-7: New USB device found, idVendor=1fc9, idProduct=00a4, bcdDevice= 1.01

[233102.781299] usb 1-7: New USB device strings: Mfr=1, Product=2, SerialNumber=0

[233108.354021] usb 1-7: parse_audio_format_rates_v2v3(): unable to retrieve number of sample rates (clock 16)

[233113.474359] usb 1-7: parse_audio_format_rates_v2v3(): unable to retrieve number of sample rates (clock 16)

[233118.593224] usb 1-7: cannot get ctl value: req = 0x83, wValue = 0x200, wIndex = 0x200, type = 4

[233118.593228] usb 1-7: 2:0: cannot get min/max values for control 2 (id 2)

[233123.714658] usb 1-7: cannot get ctl value: req = 0x83, wValue = 0x200, wIndex = 0x500, type = 4

[233123.714665] usb 1-7: 5:0: cannot get min/max values for control 2 (id 5)

[233123.715896] usb 1-7: 4:1 : bogus bTerminalLink 9

[233124.117917] usb 1-7: 5:1 : bogus bTerminalLink 10

[233129.344734] usb 1-7: cannot get ctl value: req = 0x83, wValue = 0x200, wIndex = 0x803, type = 4

[233129.344739] usb 1-7: 8:3: cannot get min/max values for control 2 (id 8)

[233134.464652] usb 1-7: cannot get ctl value: req = 0x83, wValue = 0x200, wIndex = 0xb03, type = 4

[233134.464657] usb 1-7: 11:3: cannot get min/max values for control 2 (id 11)

[233139.584766] usb 1-7: cannot get ctl value: req = 0x83, wValue = 0x200, wIndex = 0x500, type = 4

[233139.584770] usb 1-7: 5:0: cannot get min/max values for control 2 (id 5)

[233144.704744] usb 1-7: cannot get ctl value: req = 0x83, wValue = 0x200, wIndex = 0x500, type = 4

[233144.704749] usb 1-7: 5:0: cannot get min/max values for control 2 (id 5)

[233149.825169] usb 1-7: cannot get ctl value: req = 0x83, wValue = 0x200, wIndex = 0x500, type = 4

[233149.825173] usb 1-7: 5:0: cannot get min/max values for control 2 (id 5)

[233154.945395] usb 1-7: cannot get ctl value: req = 0x83, wValue = 0x200, wIndex = 0x500, type = 4

[233154.945400] usb 1-7: 5:0: cannot get min/max values for control 2 (id 5)

[233160.065816] usb 1-7: cannot get ctl value: req = 0x83, wValue = 0x200, wIndex = 0x500, type = 4

[233160.065821] usb 1-7: 5:0: cannot get min/max values for control 2 (id 5)

[233165.185114] usb 1-7: cannot get ctl value: req = 0x83, wValue = 0x200, wIndex = 0x500, type = 4

[233165.185119] usb 1-7: 5:0: cannot get min/max values for control 2 (id 5)

[233165.680270] usb 1-7: cannot get ctl value: req = 0x81, wValue = 0x200, wIndex = 0x500, type = 4

[233165.680667] usb 1-7: cannot get ctl value: req = 0x81, wValue = 0x200, wIndex = 0x500, type = 4

[233165.681407] usb 1-7: cannot get ctl value: req = 0x81, wValue = 0x200, wIndex = 0x500, type = 4

[233165.682086] usb 1-7: cannot get ctl value: req = 0x81, wValue = 0x100, wIndex = 0x500, type = 1

[233165.682427] usb 1-7: cannot get ctl value: req = 0x83, wValue = 0x200, wIndex = 0xb03, type = 4

[233165.682430] usb 1-7: 11:3: cannot get min/max values for control 2 (id 11)

mrecoskie · ‎02-16-2022

True. However there are multiple Audio Control Interfaces in the definition above - one for each device. Interface 0 and 3. In theory the same IDs could be used because they are in different Audio Control interfaces?

    Interface Descriptor:

      bLength                 9

      bDescriptorType         4

      bInterfaceNumber        0

      bAlternateSetting       0

      bNumEndpoints           0

      bInterfaceClass         1 Audio

      bInterfaceSubClass      1 Control Device

      bInterfaceProtocol     32 

      iInterface              0 




…




    Interface Descriptor:

      bLength                 9

      bDescriptorType         4

      bInterfaceNumber        3

      bAlternateSetting       0

      bNumEndpoints           0

      bInterfaceClass         1 Audio

      bInterfaceSubClass      1 Control Device

      bInterfaceProtocol     32 

      iInterface              0

jingpan · ‎02-16-2022

Hi @mrecoskie ,

Yes, I think so.

Regards,

Jing

mrecoskie · ‎02-17-2022

Hi Jing. Mirroring the indices from the first device to the second device did in fact work.

jingpan · ‎02-16-2022

Hi @mrecoskie ,

I'm not familiar with UAC. But I see in USB Audio Class 2.0 spec, it says

Regards,

Jing

USB Audio Descriptor - multiple devices, one usb connection

USB Audio Descriptor - multiple devices, one usb connection

i.MXRT 106x