I recently received my Hifiberry DAC+ Pro, using it with Openelec 6.0.0 (linux kernel 4.1.12). I used the Hifiberry Installer to get the RPI2 recognising the board, using gold plated RCA cables to connect to AUX on the Bose 321 2.1 soundsystem: http://worldwide.bose.com/productsupport/en_us/web/321gs_series2/page.html
Here's my settings:
As you can see, passthrough output is greyed out and stuck on "PI: HDMI"
If passthrough is enabled, when I playback most of my video, there's no audio. If I increase the audio on the actual TV (ie via HDMI) there is horrible white noise.
Hifiberry DAC+ Pro and OpenElec passthrough enabled == white noise