Channel count in GoXLR SplitPCM configuration

[pv]

Similar issue as #515, and related to #444:

We have a report https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/4602 that GoXLR UCM profile with SplitPCM=1 specifies always 23 channels, but the device can't be opened with exactly 23 channels. According to https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/4602#note_2819696 the device may have 21, 23, or 25 depending on firmware/etc details.

In Pipewire, I think we add a workaround that just uses the available channel count even if it is different from what UCM profile specifies, but logs warnings if the counts are different so these issues in the profiles can be caught.

[perexg]

In Pipewire, I think we add a workaround that just uses the available channel count even if it is different from what UCM profile specifies, but logs warnings if the counts are different so these issues in the profiles can be caught.

I don't think that it's the right way to do. Those are really specific issue which should be resolved in UCM. Probably, we can parse /proc/card#/stream0 contents to know the number of channels for this device. I'm closing this as a dup of #444.

[pv]

I don't think that it's the right way to do.

I agree. However, we need a workaround for the short term, as we need something to address this as it's a regression that makes audio devices disappear in PW 1.4.0 (which now uses the SpliPCM UCM profiles).

[perexg]

Users can fix the UCM configuration files manually for now. If wireplumber continues with detection - nobody will care to fix this properly. Warnings are not enough.