USB Control Transfers on Devices with CDC Serial Port

I have a USB-device with three interfaces:

  • Vendor-Specific Bulk
  • CDC Serial Control
  • CDC Serial Data

To configure the vendor specific bulk endpoints I need to send vendor specific control requests to endpoint 0. I'm using libusb for this task. As long as the interfaces for the CDC serial port are present I get an access error when trying to send vendor control requests.

If I disable these CDC interfaces I can send vendor control request without any problems:

Is this by design or ist there any possibility to send vendor control requests to the USB device while a CDC driver is active?

USB Control Transfers on Devices with CDC Serial Port
 
 
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