vc4.ko brings unusable&unstable ALSA sinks

[Ryutaroh Matsumoto]

Hi again,

>> Raspberry Pi OS kernel latest version now works fine with pulseaudio.
> Is that a 32bit or 64bit kernel? AFAIK, all the problems are with 64bit.

It's 64-bit.
It is funny that 32-bit kernel works fine while 64-bit doesn't...
The only problem in 64-bit Raspberry Pi kernel that I know is that
gnome-shell wayland doesn't work and drawing collapses,
which is a bug in gnome-shell and not in the kernel.

> I previously asked what the role/purpose was of vc4hdmi, but got no answer.
> So I don't know if I should use one OR the other or that they're supposed to 
> work together in 'some' way.

I am pretty sure that vc4hdmi does not work in the same way as
snd_bcm2835.ko, as most of aplay commands fail with vc4hdmi
while they succeed with snd_bcm2835.
"aplay" behaves very differently with vc4hdmi and snd_bcm2835.

In addition RPi4B has two HDMI outputs, but snd_bcm2835 does not
show two HDMIs... The second HDMI can probably only be accessed via vc4.ko.

If they are  supposed to work in the same way, someone should file a bug report.

On the other hand, with module_blacklist=snd_bcm2835,
vc4hdmi shows no problem with the default Debian setting
of pulseaudio (user-mode) on RPi4B 8GB...

As I do not have a multi-channel device, I have no idea on
multi-channel functioning...

Best regards, Ryutaroh