Re: snd-usb-audio : issue sending "set sample freq"

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On 22.04.2013 21:23, Torstein Hegge wrote:
> On Mon, Apr 22, 2013 at 20:44:40 +0200, Daniel Mack wrote:
>> Also, the lsusb dumps don't contain a audio specific header descriptor,
>> which normally looks like this:
>>
>>         AudioControl Endpoint Descriptor:
>>           bLength                 7
>>           bDescriptorType        37
>>           bDescriptorSubtype      1 (EP_GENERAL)
>>           bmAttributes         0x01
>>             Sampling Frequency
>>           bLockDelayUnits         0 Undefined
>>           wLockDelay              0 Undefined
>>
>> And without the "Sampling Frequency" bit in bmAttributes, the driver
>> will bail out early (clock.c):
> 
> I think it has the class specific endpoint descriptor, but it is in
> front of the standard endpoint descriptor. From the 'lsusb -v':
> 
>        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]        16000
>          tSamFreq[ 1]        48000
>        ** UNRECOGNIZED:  07 25 01 81 02 00 00
>        Endpoint Descriptor:
>          bLength                 9
>          bDescriptorType         5
>          bEndpointAddress     0x03  EP 3 OUT
>          bmAttributes            1
>            Transfer Type            Isochronous
>            Synch Type               None
>            Usage Type               Data
>          wMaxPacketSize     0x00c0  1x 192 bytes
>          bInterval               1
>          bRefresh                0
>          bSynchAddress           0
> 
> The UNRECOGNIZED bit matches the missing AudioControl endpoint
> descriptor.

Ah, yes, good catch.

> Even if this is against the specification, devices that does this is out
> there. I have seen the same thing on a Sennheiser BTD-500, but that only
> supports one frequency, so I didn't hit this problem.

Yes, if that's the case, we should patch both lsusb and the snd-usb
driver. Let's see who provides a patch first :)


Daniel


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