Can more than one application claim an interface in libusb?

Question

I am working on a hardware/software application where, connected via usb, is a device that does some off board processing on some data. The application is meant to be open multiple times and which device needs which data is identified by an in-stream parameter. My question is, can more than one application claim an interface? my first implementation used WinUSB but I quickly realized that that limits me to only one instance. The libusb documentation claims that this limitation is removed in their driver.

My concern is, because I intend to have far more than 8 instances running, having only the 8 interfaces allotted will not be sufficient. If I cannot, in fact, claim an interface more than once, is there a method where I could have the applications call a shared library that claims the interface and manages and routes traffic between the applications?

Answer 1

As far as I know you can only have one handle open to a device in either implementation.

I think you are on track in terms of how to handle this problem. The way I have done something like this in the past is to create a service that is to run in the background. This service should be launched by the first instance of the application, and can keep a reference count of it's clients. On your next instance of the application increment your reference count, and whenever a client application closes decrement the reference count. When the last application closes the service can close too.

The service would have the job of opening the device and reading all data in to a buffer. From there you can either put smarts in to the service to process the data and load it in to different shared buffers that are each individually accessible by your other client application instances, or you could simply make one huge buffer available to everyone (but this is a riskier solution).