On Sat, May 09, 2015 at 07:49:44PM +0300, Anssi Hannula wrote:
(Of course having userspace set them requires that the device has a proper entry in /usr/share/alsa/cards and the pcm device is accessed via the standard "hdmi" or "iec958" device names which perform the channel status word setup. I guess the ARM SoC stuff generally doesn't bother with that, explaining a bit why some kernel drivers set them by themselves).
I'm not sure that's sufficient - I haven't yet found where in the ALSA userspace, the AES bits are appropriately set according to the sample rate.
HDMI_FC_AUDICONF2 register default value is 0x00, which means plain stereo (per CEA-861). If this is what goes on to the HDMI link as well, the audio sink should ignore the other channels. Did you check that multichannel PCM actually works? (maybe I'm just missing where CA is set)
I have no way to test multichannel support - not everyone has a plethora of HDMI devices readily accessible.