* USB-Audio: fix channel count for SSL 2+ Mk II
[not found] <alsa-project/alsa-ucm-conf/pr/854@alsa-project.org>
@ 2026-09-12 19:43 ` GitHub pull_request - opened
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From: GitHub pull_request - opened @ 2026-09-12 19:43 UTC (permalink / raw)
To: alsa-devel
alsa-project/alsa-ucm-conf pull request #854 was opened from zachberger:
The "SSL 2+ Mk II" reports the same USB product ID (31e9:0009) as the plain "SSL 2 Mk II", so the existing detection based on CardComponents and bcdDevice cannot tell them apart. It has more physical I/O though: 6 playback channels and 8 capture channels, vs 4/4 for the plain model.
With the previous profile (DirectPlaybackChannels=4, DirectCaptureChannels=4), WirePlumber rejects the whole card:
spa.alsa: Error in ALSA UCM profile for _ucm0003.hw:II,0 (HiFi: Line2: sink): PlaybackChannels=4 < avail 6
spa.alsa: Error in ALSA UCM profile for _ucm0003.hw:II,0 (HiFi: Mic2: source): CaptureChannels=4 < avail 8
spa.alsa: Errors in ALSA UCM profile for card SSL 2+ Mk II
...and it shows up as "SSL 2+ Mk II [ALSA UCM error]" in wpctl/sound pickers built on PipeWire.
Disambiguate using the USB product string (which does carry the "+"), read via sys-card the same way bcdDevice already is, and set the correct channel counts for the confirmed "SSL 2+ Mk II" case.
The If.chn4 gate in SSL2-HiFi.conf that builds the split Line1/Line2 output devices only matched DirectPlaybackChannels == "4" exactly. Broaden it to match "4" or "6" so the "+" Mk II also gets routed through the existing channel-splitting macros (which already use the variable dynamically and needed no other change).
Tested against real "SSL 2+ Mk II" hardware (USB ID 31e9:0009, bcdDevice 0116, 6 playback / 8 capture channels per USB descriptors). Before: card flagged with [ALSA UCM error], no usable output. After: clean profile, Line1/Line2 both work as separate stereo outputs, Mic1/Mic2 both work as separate mono inputs.
Not extended to the non-Mk-II "SSL 2+" since that hardware wasn't available to verify its channel counts also come out to 6/8.
[alsa-info-ssl2plus.txt](https://github.com/user-attachments/files/32149222/alsa-info-ssl2plus.txt)
Request URL : https://github.com/alsa-project/alsa-ucm-conf/pull/854
Patch URL : https://github.com/alsa-project/alsa-ucm-conf/pull/854.patch
Repository URL: https://github.com/alsa-project/alsa-ucm-conf
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