Hi Dragan,
Using the Linux IPU driver, it's not possible to specify what IPU will be used. The driver handles it automatically and assigns each task for the available IPU.
If you want to use both IPUs at the same time (e.g. to process a specific task faster using 2 IPUs), you can open /dev/mxc_ipu once, create 2 threads and call the iotcl to perform the operation you want inside each thread.
I tried this approach and it works.
Rgds
Rogerio