This is the current also conf we embed: https://github.com/chewitt/alsa-l…sound-card.conf
This is an older version: https://github.com/chewitt/alsa-l…sound-card.conf
The older conf has all the analogue device pcm extras needed for speaker-test to work with multiple channels. In the absence of all of them (as per the current conf) speaker-test will only output stereo since this is all the default pcm device supports/exposes. This is 100% same on my system; which happily outputs multi-channel PCM and PT on the HDMI connection (which is not the analogue pcm device). So kudos for playing "spot the difference" .. but this difference is not the thing you are looking for.
NB: The only reason the older conf exists was an earlier attempt to work around a driver not-technically-a-bug where alsa does not pass mixer controls correctly. This patch hacks a fix: https://github.com/chewitt/linux/…702a070dc71c133
I'd ask that you play with cables and AVR/TV ports. Multi-channel output depends on the ELD data read from EDID/HDMI and the usual "but it works in the legacy image!" claim means little due to a) the upstream codebase being 100% different, and b) the amount of hideous stuff the legacy kernel ignores/overrides/fakes to work around TVs and monitors that provide bad/broken EDID data.
And yes the greatest percentage of AMLGX users are probably using default 2-channel output. However, enough folks have complained about the earlier multi-channel state (that the kernel patch resolved) that I know people are using multi-channel output.
