iMX8QM HDMI input audio issue when HDMI cable is unplugged

[stephanhoffmann]

When a HDMI source is connected to the HDMI Input of iMX8QM I can access it with v4l2 (e.g. v4l2-ctl --list-devices) and alsa (e.g. arecord -l or arecord -D hw:1 -f S16_LE -r 48000 -c 2 /tmp/record).

When I do not have a HDMI source connected v4l2-ctl --list-devices does not list the device which I consider expected behaviour. Also the video device /dev/videox is not present in this case.

At the same time arecord -l still lists the HDMI rx audio device, but it does not work, arecord gives an error message:

# arecord -D hw:1 -f S16_LE -r 48000 -c 2 /tmp/record
arecord: main:831: audio open error: Invalid argument

 As of my understanding ALSA should work the same as v4l2 in this regard.

I am using a custom image based on NXP Linux kernel lf-6.1.1-1.0.0 from https://github.com/nxp-imx/linux-imx on a custom board.

I observed the same behavior with a iMX8QM MEK running NXP i.MX Release Distro 6.6-nanbield with kernel 6.6.3-lts-next-gccf0a99701a7.

[JorgeCas]

Hello,

It seems that does not update the card list when RX HDMI device is unplugged, and takes the last list configuration in:

/proc/asound/cards

Best regards.

[stephanhoffmann]

Thank you for replying, JorgeCas, but that's obvious.

The question is: Is this considered a bug that might get fixed sometimes in the future? Is NXP already aware of this and working on it?

Kind regards

Stephan

[JorgeCas]

Hello,

ALSA enumerates the sound cards according to the device tree configuration and it is not updated until reboot. That is an expected behavior.

Best regards.

[JorgeCas]

Hello,

This is not reported as a bug. Let me check if internal team knows about this behavior and confirm if this is an expected behavior.

Best regards.

[stephanhoffmann]

Thanks!