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.
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.
Torstein
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