Re: [alsa-devel] Jack sensing in snd_usb_audio ?

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On Wed, 12 Oct 2016 18:15:04 +0200,
Bastien Nocera wrote:
> 
> On Wed, 2016-10-12 at 18:06 +0200, Clemens Ladisch wrote:
> > Bastien Nocera wrote:
> > > On Wed, 2016-10-12 at 14:43 +0200, Clemens Ladisch wrote:
> > > > Bastien Nocera wrote:
> > > > > "
> > > > > A change of state in the audio function is most often caused by
> > > > > a
> > > > > certain event that takes place. An event can either be user-
> > > > > initiated
> > > > > or device-initiated. User-initiated jack insertion or removal
> > > > > is a
> > > > > typical example of a user-initiated event.
> > > > > "
> > > > 
> > > > 
> > > > There are not many USB Audio 2.0 devices, and I'm not aware of
> > > > any
> > > > that actually implements this.
> > > 
> > > 
> > > I guess I would see whether there are events if I captured the USB
> > > traffic even without special handling/turning on a feature in the
> > > drivers, right?
> > 
> > 
> > Most devices do not even have the status endpoint (see "lsusb -v").
> > To check what events arrive, you can add logging to the
> > snd_usb_mixer_interrupt() function.
> 
> I'm guessing it doesn't support it then (see attached log)

So this looks like a HID, not from the audio device class.
It's an oft-seen implementation.

> I also checked the input device output when plugging in something, with
> evtest, and no feedback either.

Then at first you need to hack a HID driver to support this device.
It'll create an input device, and then we'll need to find some way to
couple the given input device and the audio device.  We can parse the
sysfs device path to figure out, but I'm not sure what's the best way
to tell it to applications.


Takashi

> Bus 003 Device 035: ID 1b3f:2008 Generalplus Technology Inc. 
> Device Descriptor:
>   bLength                18
>   bDescriptorType         1
>   bcdUSB               1.10
>   bDeviceClass            0 
>   bDeviceSubClass         0 
>   bDeviceProtocol         0 
>   bMaxPacketSize0         8
>   idVendor           0x1b3f Generalplus Technology Inc.
>   idProduct          0x2008 
>   bcdDevice            1.00
>   iManufacturer           1 GeneralPlus
>   iProduct                2 USB Audio Device
>   iSerial                 0 
>   bNumConfigurations      1
>   Configuration Descriptor:
>     bLength                 9
>     bDescriptorType         2
>     wTotalLength          253
>     bNumInterfaces          4
>     bConfigurationValue     1
>     iConfiguration          0 
>     bmAttributes         0x80
>       (Bus Powered)
>     MaxPower              100mA
>     Interface Descriptor:
>       bLength                 9
>       bDescriptorType         4
>       bInterfaceNumber        0
>       bAlternateSetting       0
>       bNumEndpoints           0
>       bInterfaceClass         1 Audio
>       bInterfaceSubClass      1 Control Device
>       bInterfaceProtocol      0 
>       iInterface              0 
>       AudioControl Interface Descriptor:
>         bLength                10
>         bDescriptorType        36
>         bDescriptorSubtype      1 (HEADER)
>         bcdADC               1.00
>         wTotalLength          100
>         bInCollection           2
>         baInterfaceNr( 0)       1
>         baInterfaceNr( 1)       2
>       AudioControl Interface Descriptor:
>         bLength                12
>         bDescriptorType        36
>         bDescriptorSubtype      2 (INPUT_TERMINAL)
>         bTerminalID             1
>         wTerminalType      0x0101 USB Streaming
>         bAssocTerminal          0
>         bNrChannels             2
>         wChannelConfig     0x0003
>           Left Front (L)
>           Right Front (R)
>         iChannelNames           0 
>         iTerminal               0 
>       AudioControl Interface Descriptor:
>         bLength                12
>         bDescriptorType        36
>         bDescriptorSubtype      2 (INPUT_TERMINAL)
>         bTerminalID             4
>         wTerminalType      0x0201 Microphone
>         bAssocTerminal          0
>         bNrChannels             1
>         wChannelConfig     0x0001
>           Left Front (L)
>         iChannelNames           0 
>         iTerminal               0 
>       AudioControl Interface Descriptor:
>         bLength                 9
>         bDescriptorType        36
>         bDescriptorSubtype      3 (OUTPUT_TERMINAL)
>         bTerminalID             3
>         wTerminalType      0x0301 Speaker
>         bAssocTerminal          0
>         bSourceID               6
>         iTerminal               0 
>       AudioControl Interface Descriptor:
>         bLength                 9
>         bDescriptorType        36
>         bDescriptorSubtype      3 (OUTPUT_TERMINAL)
>         bTerminalID             2
>         wTerminalType      0x0101 USB Streaming
>         bAssocTerminal          0
>         bSourceID               9
>         iTerminal               0 
>       AudioControl Interface Descriptor:
>         bLength                 7
>         bDescriptorType        36
>         bDescriptorSubtype      5 (SELECTOR_UNIT)
>         bUnitID                 9
>         bNrInPins               1
>         baSource( 0)            5
>         iSelector               0 
>       AudioControl Interface Descriptor:
>         bLength                10
>         bDescriptorType        36
>         bDescriptorSubtype      6 (FEATURE_UNIT)
>         bUnitID                 6
>         bSourceID               8
>         bControlSize            1
>         bmaControls( 0)      0x01
>           Mute Control
>         bmaControls( 1)      0x02
>           Volume Control
>         bmaControls( 2)      0x02
>           Volume Control
>         iFeature                0 
>       AudioControl Interface Descriptor:
>         bLength                 9
>         bDescriptorType        36
>         bDescriptorSubtype      6 (FEATURE_UNIT)
>         bUnitID                 5
>         bSourceID               4
>         bControlSize            1
>         bmaControls( 0)      0x43
>           Mute Control
>           Volume Control
>           Automatic Gain Control
>         bmaControls( 1)      0x00
>         iFeature                0 
>       AudioControl Interface Descriptor:
>         bLength                 9
>         bDescriptorType        36
>         bDescriptorSubtype      6 (FEATURE_UNIT)
>         bUnitID                 7
>         bSourceID               4
>         bControlSize            1
>         bmaControls( 0)      0x03
>           Mute Control
>           Volume Control
>         bmaControls( 1)      0x00
>         iFeature                0 
>       AudioControl Interface Descriptor:
>         bLength                13
>         bDescriptorType        36
>         bDescriptorSubtype      4 (MIXER_UNIT)
>         bUnitID                 8
>         bNrInPins               2
>         baSourceID( 0)          1
>         baSourceID( 1)          7
>         bNrChannels             2
>         wChannelConfig     0x0003
>           Left Front (L)
>           Right Front (R)
>         iChannelNames           0 
>         bmControls         0x00
>         iMixer                  0 
>     Interface Descriptor:
>       bLength                 9
>       bDescriptorType         4
>       bInterfaceNumber        1
>       bAlternateSetting       0
>       bNumEndpoints           0
>       bInterfaceClass         1 Audio
>       bInterfaceSubClass      2 Streaming
>       bInterfaceProtocol      0 
>       iInterface              0 
>     Interface Descriptor:
>       bLength                 9
>       bDescriptorType         4
>       bInterfaceNumber        1
>       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           1
>         bDelay                  1 frames
>         wFormatTag              1 PCM
>       AudioStreaming Interface Descriptor:
>         bLength                14
>         bDescriptorType        36
>         bDescriptorSubtype      2 (FORMAT_TYPE)
>         bFormatType             1 (FORMAT_TYPE_I)
>         bNrChannels             2
>         bSubframeSize           2
>         bBitResolution         16
>         bSamFreqType            2 Discrete
>         tSamFreq[ 0]        44100
>         tSamFreq[ 1]        48000
>       Endpoint Descriptor:
>         bLength                 9
>         bDescriptorType         5
>         bEndpointAddress     0x05  EP 5 OUT
>         bmAttributes            1
>           Transfer Type            Isochronous
>           Synch Type               None
>           Usage Type               Data
>         wMaxPacketSize     0x00c0  1x 192 bytes
>         bInterval               1
>         bRefresh                0
>         bSynchAddress           0
>         AudioControl Endpoint Descriptor:
>           bLength                 7
>           bDescriptorType        37
>           bDescriptorSubtype      1 (EP_GENERAL)
>           bmAttributes         0x01
>             Sampling Frequency
>           bLockDelayUnits         0 Undefined
>           wLockDelay              0 Undefined
>     Interface Descriptor:
>       bLength                 9
>       bDescriptorType         4
>       bInterfaceNumber        2
>       bAlternateSetting       0
>       bNumEndpoints           0
>       bInterfaceClass         1 Audio
>       bInterfaceSubClass      2 Streaming
>       bInterfaceProtocol      0 
>       iInterface              0 
>     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           2
>         bDelay                  1 frames
>         wFormatTag              1 PCM
>       AudioStreaming Interface Descriptor:
>         bLength                14
>         bDescriptorType        36
>         bDescriptorSubtype      2 (FORMAT_TYPE)
>         bFormatType             1 (FORMAT_TYPE_I)
>         bNrChannels             1
>         bSubframeSize           2
>         bBitResolution         16
>         bSamFreqType            2 Discrete
>         tSamFreq[ 0]        44100
>         tSamFreq[ 1]        48000
>       Endpoint Descriptor:
>         bLength                 9
>         bDescriptorType         5
>         bEndpointAddress     0x86  EP 6 IN
>         bmAttributes            1
>           Transfer Type            Isochronous
>           Synch Type               None
>           Usage Type               Data
>         wMaxPacketSize     0x0064  1x 100 bytes
>         bInterval               1
>         bRefresh                0
>         bSynchAddress           0
>         AudioControl Endpoint Descriptor:
>           bLength                 7
>           bDescriptorType        37
>           bDescriptorSubtype      1 (EP_GENERAL)
>           bmAttributes         0x01
>             Sampling Frequency
>           bLockDelayUnits         0 Undefined
>           wLockDelay              0 Undefined
>     Interface Descriptor:
>       bLength                 9
>       bDescriptorType         4
>       bInterfaceNumber        3
>       bAlternateSetting       0
>       bNumEndpoints           1
>       bInterfaceClass         3 Human Interface Device
>       bInterfaceSubClass      0 
>       bInterfaceProtocol      0 
>       iInterface              0 
>         HID Device Descriptor:
>           bLength                 9
>           bDescriptorType        33
>           bcdHID               2.01
>           bCountryCode            0 Not supported
>           bNumDescriptors         1
>           bDescriptorType        34 Report
>           wDescriptorLength      41
>          Report Descriptors: 
>            ** UNAVAILABLE **
>       Endpoint Descriptor:
>         bLength                 7
>         bDescriptorType         5
>         bEndpointAddress     0x83  EP 3 IN
>         bmAttributes            3
>           Transfer Type            Interrupt
>           Synch Type               None
>           Usage Type               Data
>         wMaxPacketSize     0x0008  1x 8 bytes
>         bInterval              32
> Device Status:     0x0000
>   (Bus Powered)
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