[Libusb-devel] MacOSX: Accessing multiple interfaces of the same device at once

[Emmanuel B. <ebl...@gm...>]

Hi All,

I was wondering what is the recommended way, on Mac OS X (10.5/10.6),
to access multiple interfaces of the same device, from the same process ?

It seems that opening the same device twice or more is not allowed,
as the libusb_open() call silently fails:

The call sequence looks like the following:
usb_open
  libusb_open
    darwin_open
      USBDeviceOpenSeize

fails with the kIOReturnExclusiveAccess error.
darwin_open silently discards the error, and resume execution.

Then the following call sequence is executed to perform a USB reset

usb_control_msg
  libusb_control_transfer
    libusb_submit_transfer
      darwin_submit_transfer
        submit_control_transfer
          DeviceRequestAsyncTO

which fails with kIOUSBNoAsyncPortErr as the CreateDeviceAsyncEventSource()
never got called in the previous darwin_open() invokation.

So what would be the proper way to open a single device and use several
interfaces at once ?

Thanks in advance,
Manu

(using the latest libusb release, 1.0.4)