I have an intra-**** video device that's supported by Apple's AVCaptureDevice. I can use the AV classes to connect to the device and get video. However, this device has a button that's used to acquire still images from the video stream. I can't use the IOUSBDeviceInterface to do an asynchronous read, because the Apple driver has the device opened exclusively. How do I go about receiving the button event in this scenario? I know which pipe to read, based on a bus analyzer when I run this on Windows, I just need to know how to access that pipe when the device is opened by another process.
The Apple driver has the UVC interface open all the time when the device is streaming, but not the device interface. You can send device commands or receive status over pipe 0. You would have to poll to get the button press.
What platform is this on - macOS, or iPadOS? On macOS, if your button exposes a HID interface, you can use HID manager routines to get notifications of reports on the interrupt pipe. The system will attach its own driver to a keyboard or mouse, but it will leave a vendor-specific HID device alone, so your code can talk to it.