[alsa-devel] UCM file lookup logic

[Jaroslav Kysela]

Dne 27. 01. 20 v 4:38 Tanu Kaskinen napsal(a):
> Hi all,
> 
> I was looking at the UCM files, and most paths have the following
> structure:
> 
>      <cardname>/<cardname>.conf
> 
> I noticed that the "HDA Intel PCH" configuration uses some other
> scheme:
> 
>      HDA Intel PCH/HDAudio-DualCodecs.conf
>      HDA Intel PCH/HDAudio-Gigabyte-ALC1220DualCodecs.conf
>      HDA Intel PCH/HDAudio-Lenovo-DualCodecs.conf
> 
> How are the directory and file names determined? If I write
> configuration for some random sound card that I don't have myself,
> where do I find the various identifiers in the alsa-info output? I
> don't even really know for sure what the <cardname> in the first
> example is, I've been assuming it's the name that appears in the square
> brackets in /proc/asound/cards.

The ucm has scheme <longname>/<longname>.conf and 
<drivername>/<drivername>.conf (fallback).

The ucm2 has scheme <drivername>/<longname>.conf and
<drivername>/<drivername>.conf (fallback).

Example proc output:

  2 [device         ]: USB-Audio - USB Video device
                       317GAWCM001LON3BC1AZ USB Video device at 
usb-0000:00:14.0-4.2.4, high speed

The driver name is 'USB-Audio' here. The longname is '317GAWCM001LON3BC1AZ USB 
Video device at usb-0000:00:14.0-4.2.4, high speed' here. The name in brackets 
is the user selectable identifier for the card (card id). It can be used 
instead the sound card number.

> I think the lookup logic should be explained in the ucm2/README.md
> file. I can write a patch if someone expains the logic to me, but
> probably it's easier if you just write the patch yourself.

Yes, a better documentation for the internals is missing. Unfortunately, I hit 
other real problems with the current UCM logic and trying to resolve them. 
Unfortunately, I am interrupted with other things so things are going slowly 
than I want.

Actually, I am working on a UCM configuration verification tool.

					Jaroslav

-- 
Jaroslav Kysela <perex at perex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.