[linux-usb-devel] Changing default Configuration of a usb device.

[Dwaine Garden]

We are trying to get our device to use another configuration other than 
the default configuration.  We are trying to get the audio over usb 
working on the device.   The third endpoint does not appear active if we 
use configuration #1, it's only active if configuration #2 and higher is 
used.

All the drivers do not handle devices with multiple configurations very 
well.   I could not locate any sample code to change the default 
configuration.

/* We don't handle multi-config */
   /*
   if (dev->descriptor.bNumConfigurations != 1)
       return NULL;
   */
Here is the example of configuration 1.  Only two endpoint, which 
neither are the audio endpoint.

C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=200mA
I:  If#= 0 Alt= 1 #EPs= 2 Cls=00(>ifc ) Sub=00 Prot=00 Driver=USBVision 
Video Grabber
E:  Ad=01(B) Atr=00(Ctrl) MxPS=   8 Ivl=0ms
E:  Ad=82(I) Atr=01(Isoc) MxPS= 959 Ivl=1ms

Here is the configuration I'm trying to have the usbvision device use.
C:  #Ifs= 1 Cfg#= 2 Atr=80 MxPwr=200mA
I:  If#= 0 Alt= 1 #EPs= 3 Cls=00(>ifc ) Sub=00 Prot=00 Driver=
E:  Ad=01(B) Atr=00(Ctrl) MxPS=   8 Ivl=0ms
E:  Ad=82(I) Atr=01(Isoc) MxPS= 959 Ivl=1ms
E:  Ad=83(I) Atr=01(Isoc) MxPS=  66 Ivl=1ms <-----  This is the audio 
endpoint!!!!!1111

I have also read that the configuration of a usb device is handled by 
the usb-core, and can not be changed.   Is this true?

I'm looking for some hints on how to code the change to configuration #2.
Thanks
Dwaine. 


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