Multiple error messages on Raspberry Pi 4 using the vc4-hdmi ALSA device

[vanfanel]

Describe the bug

On Raspberry PI OS 64bit (aarch64), if the vc4-hdmi device is used, running any PortAudio program causes multiple errors on the console. With the sine example:

PortAudio Test: output sine wave. SR = 44100, BufSize = 64
ALSA lib pcm_asym.c:105:(_snd_pcm_asym_open) capture slave is not defined
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.front
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround21
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround21
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround40
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround41
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround50
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround51
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround71
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.iec958
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.iec958
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.iec958
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.modem
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.modem
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.phoneline
ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.phoneline
ALSA lib pcm_asym.c:105:(_snd_pcm_asym_open) capture slave is not defined
ALSA lib pcm_direct.c:1206:(snd1_pcm_direct_initialize_slave) requested or auto-format is not available
ALSA lib pcm_dmix.c:1087:(snd_pcm_dmix_open) unable to initialize slave
Play for 5 seconds.

It works after all those errors, but messages are somewhat worrying.

To Reproduce
Steps to reproduce the behavior. Include code if applicable.

1. Activate the vc4-hdmi audio device, by having dtoverlay=vc4-kms-v3d and commenting out dtparam=audio=on
2. Try a PortAudio test.

Expected behavior
PortAudio programs should work without errors.

Desktop (please complete the following information):

• OS: Raspberry Pi OS aarch64
• OS Version: Debian 11 (Latest stable)
• PortAudio version: current (please give date and/or Git hash): 68e963a
• If Windows or Linux, which Host API (e.g. WASAPI): GNU/Linux - ALSA

Additional information

The vc4-hdmi ALSA device configuration is exactly this one:
https://github.com/alsa-project/alsa-lib/blob/master/src/conf/cards/vc4-hdmi.conf

[RossBencina]

Possible duplicate #739, #555, #163