vc4.ko brings unusable&unstable ALSA sinks

[Ryutaroh Matsumoto]

Hi Diederik,

Thank you for your response and sorry for my emails not being much helpful...

> In both cases mpd started playing but I heard nothing.
> diederik at rpi-mpd:~$ aplay -l
> diederik at rpi-mpd:~$ pactl list cards

It should work... At least I had no problem under similar situations...

> In both cases mpd started playing but I heard nothing.

vc4.ko's HDMI audio output works fine with my RPi4B,
but I am not very sure if vc4.ko works with HDMI audio of your RPi3.

My weak suggestions are
(1) module_blacklist=vc4 if you don't need it... Or
(2) Comment out load-module module-udev-detect and load-module module-detect
from /etc/pulse/default.pa, and add
load-module module-alsa-card device_id=number,
where "number" is the card number of snd_bcm2835.ko found in /proc/asound/cards.

For (2), I found that vc4.ko's HDMI audio does not work with
"module-alsa-sink" in default.pa... "module-alsa-card" works...

> And all the rest what I can find online may be dated (previously the 
> recommendation was to remove pulseaudio to get audio working, now it
> is required?),

Raspberry Pi OS kernel latest version now works fine with pulseaudio.
Their solution is to completely disable HDMI audio output of snd_bcm2835.ko,
and only vc4.ko's HDMI audio is used and enabled by them.

I hope the above is useful...

> to be configured. Thus too many variables.

I agree...
But now I probably found all the workaround to let pure Debian work
on my RPi4B with no problem... They are summarized at
https://github.com/emojifreak/debian-rpi-image-script#comments-on-linux-510-and-rapsberry-pi-4-as-of-march-2021
So far I have gotten rid of all the problem I met.

Best regards, Ryutaroh